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release/21.x: [DAG] visitFREEZE - limit freezing of multiple operands #150425

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@RKSimon RKSimon commented Jul 24, 2025

This is a partial revert of #145939 (I've kept the BUILD_VECTOR(FREEZE(UNDEF), FREEZE(UNDEF), elt2, ...) canonicalization) as we're getting reports of infinite loops (#148084).

The issue appears to be due to deep chains of nodes and how visitFREEZE replaces all instances of an operand with a common frozen version - other users of the original frozen node then get added back to the worklist but might no longer be able to confirm a node isn't poison due to recursion depth limits on isGuaranteedNotToBeUndefOrPoison.

The issue still exists with the old implementation but by only allowing a single frozen operand it helps prevent cases of interdependent frozen nodes.

I'm still working on supporting multiple operands as its critical for topological DAG handling but need to get a fix in for trunk and 21.x.

Fixes #148084

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llvmbot commented Jul 24, 2025 •
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@llvm/pr-subscribers-llvm-selectiondag
@llvm/pr-subscribers-backend-amdgpu
@llvm/pr-subscribers-backend-risc-v
@llvm/pr-subscribers-backend-nvptx

@llvm/pr-subscribers-backend-powerpc

Author: Simon Pilgrim (RKSimon)

Changes

This is a partial revert of #145939 (I've kept the BUILD_VECTOR(FREEZE(UNDEF), FREEZE(UNDEF), elt2, ...) canonicalization) as we're getting reports of infinite loops (#148084).

The issue appears to be due to deep chains of nodes and how visitFREEZE replaces all instances of an operand with a common frozen version - other users of the original frozen node then get added back to the worklist but might no longer be able to confirm a node isn't poison due to recursion depth limits on isGuaranteedNotToBeUndefOrPoison.

The issue still exists with the old implementation but by only allowing a single frozen operand it helps prevent cases of interdependent frozen nodes.

I'm still working on supporting multiple operands as its critical for topological DAG handling but need to get a fix in for trunk and 21.x.

Fixes #148084

Patch is 202.83 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/150425.diff

20 Files Affected:

  • (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+18-1)
  • (modified) llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp (+3-2)
  • (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+11-4)
  • (modified) llvm/test/CodeGen/AMDGPU/div_i128.ll (+24-40)
  • (modified) llvm/test/CodeGen/AMDGPU/rem_i128.ll (+24-40)
  • (modified) llvm/test/CodeGen/NVPTX/i1-select.ll (+15-15)
  • (modified) llvm/test/CodeGen/NVPTX/i128.ll (+290-292)
  • (modified) llvm/test/CodeGen/PowerPC/ppc64-P9-vabsd.ll (+204-213)
  • (modified) llvm/test/CodeGen/RISCV/fpclamptosat.ll (+44-44)
  • (modified) llvm/test/CodeGen/RISCV/intrinsic-cttz-elts-vscale.ll (+18-18)
  • (added) llvm/test/CodeGen/RISCV/pr148084.ll (+279)
  • (modified) llvm/test/CodeGen/RISCV/wide-scalar-shift-legalization.ll (+1018-883)
  • (modified) llvm/test/CodeGen/SystemZ/pr60413.ll (+18-18)
  • (modified) llvm/test/CodeGen/X86/abds-neg.ll (+18-18)
  • (modified) llvm/test/CodeGen/X86/avg.ll (+90-87)
  • (modified) llvm/test/CodeGen/X86/div-rem-pair-recomposition-signed.ll (+19-20)
  • (modified) llvm/test/CodeGen/X86/div-rem-pair-recomposition-unsigned.ll (+6-6)
  • (modified) llvm/test/CodeGen/X86/freeze-vector.ll (+12-12)
  • (modified) llvm/test/CodeGen/X86/pr62286.ll (+4-4)
  • (modified) llvm/test/CodeGen/X86/setcc-non-simple-type.ll (+2-2)
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 23812d795f5fa..91fd2d843f445 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -16717,7 +16717,8 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
   // Fold freeze(op(x, ...)) -> op(freeze(x), ...).
   // Try to push freeze through instructions that propagate but don't produce
   // poison as far as possible. If an operand of freeze follows three
-  // conditions 1) one-use, and 2) does not produce poison then push
+  // conditions 1) one-use, 2) does not produce poison, and 3) has all but one
+  // guaranteed-non-poison operands (or is a BUILD_VECTOR or similar) then push
   // the freeze through to the operands that are not guaranteed non-poison.
   // NOTE: we will strip poison-generating flags, so ignore them here.
   if (DAG.canCreateUndefOrPoison(N0, /*PoisonOnly*/ false,
@@ -16725,6 +16726,18 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
       N0->getNumValues() != 1 || !N0->hasOneUse())
     return SDValue();
 
+  // TOOD: we should always allow multiple operands, however this increases the
+  // likelihood of infinite loops due to the ReplaceAllUsesOfValueWith call
+  // below causing later nodes that share frozen operands to fold again and no
+  // longer being able to confirm other operands are not poison due to recursion
+  // depth limits on isGuaranteedNotToBeUndefOrPoison.
+  bool AllowMultipleMaybePoisonOperands =
+      N0.getOpcode() == ISD::SELECT_CC || N0.getOpcode() == ISD::SETCC ||
+      N0.getOpcode() == ISD::BUILD_VECTOR ||
+      N0.getOpcode() == ISD::BUILD_PAIR ||
+      N0.getOpcode() == ISD::VECTOR_SHUFFLE ||
+      N0.getOpcode() == ISD::CONCAT_VECTORS || N0.getOpcode() == ISD::FMUL;
+
   // Avoid turning a BUILD_VECTOR that can be recognized as "all zeros", "all
   // ones" or "constant" into something that depends on FrozenUndef. We can
   // instead pick undef values to keep those properties, while at the same time
@@ -16757,6 +16770,10 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
       MaybePoisonOperandNumbers.push_back(OpNo);
     if (!HadMaybePoisonOperands)
       continue;
+    if (IsNewMaybePoisonOperand && !AllowMultipleMaybePoisonOperands) {
+      // Multiple maybe-poison ops when not allowed - bail out.
+      return SDValue();
+    }
   }
   // NOTE: the whole op may be not guaranteed to not be undef or poison because
   // it could create undef or poison due to it's poison-generating flags.
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index e0597988e8907..37fddcf943681 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -778,7 +778,7 @@ SDValue TargetLowering::SimplifyMultipleUseDemandedBits(
   case ISD::FREEZE: {
     SDValue N0 = Op.getOperand(0);
     if (DAG.isGuaranteedNotToBeUndefOrPoison(N0, DemandedElts,
-                                             /*PoisonOnly=*/false))
+                                             /*PoisonOnly=*/false, Depth + 1))
       return N0;
     break;
   }
@@ -3369,7 +3369,8 @@ bool TargetLowering::SimplifyDemandedVectorElts(
   case ISD::FREEZE: {
     SDValue N0 = Op.getOperand(0);
     if (TLO.DAG.isGuaranteedNotToBeUndefOrPoison(N0, DemandedElts,
-                                                 /*PoisonOnly=*/false))
+                                                 /*PoisonOnly=*/false,
+                                                 Depth + 1))
       return TLO.CombineTo(Op, N0);
 
     // TODO: Replace this with the general fold from DAGCombiner::visitFREEZE
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 5e35d5630d667..d755c7e9bf3b3 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -45096,27 +45096,34 @@ bool X86TargetLowering::canCreateUndefOrPoisonForTargetNode(
     bool PoisonOnly, bool ConsiderFlags, unsigned Depth) const {
 
   switch (Op.getOpcode()) {
+  // SSE vector insert/extracts use modulo indices.
+  case X86ISD::PINSRB:
+  case X86ISD::PINSRW:
+  case X86ISD::PEXTRB:
+  case X86ISD::PEXTRW:
+    return false;
   // SSE vector multiplies are either inbounds or saturate.
   case X86ISD::VPMADDUBSW:
   case X86ISD::VPMADDWD:
+    return false;
   // SSE vector shifts handle out of bounds shift amounts.
   case X86ISD::VSHLI:
   case X86ISD::VSRLI:
   case X86ISD::VSRAI:
     return false;
-    // SSE blends.
+  // SSE blends.
   case X86ISD::BLENDI:
   case X86ISD::BLENDV:
     return false;
-    // SSE target shuffles.
+  // SSE target shuffles.
   case X86ISD::PSHUFD:
   case X86ISD::UNPCKL:
   case X86ISD::UNPCKH:
   case X86ISD::VPERMILPI:
   case X86ISD::VPERMV3:
     return false;
-    // SSE comparisons handle all icmp/fcmp cases.
-    // TODO: Add CMPM/MM with test coverage.
+  // SSE comparisons handle all icmp/fcmp cases.
+  // TODO: Add CMPM/MM with test coverage.
   case X86ISD::CMPP:
   case X86ISD::PCMPEQ:
   case X86ISD::PCMPGT:
diff --git a/llvm/test/CodeGen/AMDGPU/div_i128.ll b/llvm/test/CodeGen/AMDGPU/div_i128.ll
index f8e13fcdd2273..51398a45055eb 100644
--- a/llvm/test/CodeGen/AMDGPU/div_i128.ll
+++ b/llvm/test/CodeGen/AMDGPU/div_i128.ll
@@ -475,28 +475,21 @@ define i128 @v_sdiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -507,7 +500,6 @@ define i128 @v_sdiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -1043,10 +1035,10 @@ define i128 @v_sdiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    s_mov_b64 s[6:7], 1
 ; GFX9-O0-NEXT:    s_mov_b32 s5, s6
 ; GFX9-O0-NEXT:    s_waitcnt vmcnt(1)
@@ -2664,28 +2656,21 @@ define i128 @v_udiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -2696,7 +2681,6 @@ define i128 @v_udiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -3232,10 +3216,10 @@ define i128 @v_udiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    s_mov_b64 s[6:7], 1
 ; GFX9-O0-NEXT:    s_mov_b32 s5, s6
 ; GFX9-O0-NEXT:    s_waitcnt vmcnt(1)
diff --git a/llvm/test/CodeGen/AMDGPU/rem_i128.ll b/llvm/test/CodeGen/AMDGPU/rem_i128.ll
index ba9dd8f7c2468..6512bee36e88b 100644
--- a/llvm/test/CodeGen/AMDGPU/rem_i128.ll
+++ b/llvm/test/CodeGen/AMDGPU/rem_i128.ll
@@ -513,28 +513,21 @@ define i128 @v_srem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -545,7 +538,6 @@ define i128 @v_srem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -1081,10 +1073,10 @@ define i128 @v_srem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    s_mov_b64 s[6:7], 1
 ; GFX9-O0-NEXT:    s_mov_b32 s5, s6
 ; GFX9-O0-NEXT:    s_waitcnt vmcnt(1)
@@ -1897,28 +1889,21 @@ define i128 @v_urem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -1929,7 +1914,6 @@ define i128 @v_urem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -2465,10 +2449,10 @@ define i128 @v_urem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded...
[truncated]

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llvmbot commented Jul 24, 2025

@llvm/pr-subscribers-backend-systemz

Author: Simon Pilgrim (RKSimon)

Changes

This is a partial revert of #145939 (I've kept the BUILD_VECTOR(FREEZE(UNDEF), FREEZE(UNDEF), elt2, ...) canonicalization) as we're getting reports of infinite loops (#148084).

The issue appears to be due to deep chains of nodes and how visitFREEZE replaces all instances of an operand with a common frozen version - other users of the original frozen node then get added back to the worklist but might no longer be able to confirm a node isn't poison due to recursion depth limits on isGuaranteedNotToBeUndefOrPoison.

The issue still exists with the old implementation but by only allowing a single frozen operand it helps prevent cases of interdependent frozen nodes.

I'm still working on supporting multiple operands as its critical for topological DAG handling but need to get a fix in for trunk and 21.x.

Fixes #148084

Patch is 202.83 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/150425.diff

20 Files Affected:

  • (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+18-1)
  • (modified) llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp (+3-2)
  • (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+11-4)
  • (modified) llvm/test/CodeGen/AMDGPU/div_i128.ll (+24-40)
  • (modified) llvm/test/CodeGen/AMDGPU/rem_i128.ll (+24-40)
  • (modified) llvm/test/CodeGen/NVPTX/i1-select.ll (+15-15)
  • (modified) llvm/test/CodeGen/NVPTX/i128.ll (+290-292)
  • (modified) llvm/test/CodeGen/PowerPC/ppc64-P9-vabsd.ll (+204-213)
  • (modified) llvm/test/CodeGen/RISCV/fpclamptosat.ll (+44-44)
  • (modified) llvm/test/CodeGen/RISCV/intrinsic-cttz-elts-vscale.ll (+18-18)
  • (added) llvm/test/CodeGen/RISCV/pr148084.ll (+279)
  • (modified) llvm/test/CodeGen/RISCV/wide-scalar-shift-legalization.ll (+1018-883)
  • (modified) llvm/test/CodeGen/SystemZ/pr60413.ll (+18-18)
  • (modified) llvm/test/CodeGen/X86/abds-neg.ll (+18-18)
  • (modified) llvm/test/CodeGen/X86/avg.ll (+90-87)
  • (modified) llvm/test/CodeGen/X86/div-rem-pair-recomposition-signed.ll (+19-20)
  • (modified) llvm/test/CodeGen/X86/div-rem-pair-recomposition-unsigned.ll (+6-6)
  • (modified) llvm/test/CodeGen/X86/freeze-vector.ll (+12-12)
  • (modified) llvm/test/CodeGen/X86/pr62286.ll (+4-4)
  • (modified) llvm/test/CodeGen/X86/setcc-non-simple-type.ll (+2-2)
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 23812d795f5fa..91fd2d843f445 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -16717,7 +16717,8 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
   // Fold freeze(op(x, ...)) -> op(freeze(x), ...).
   // Try to push freeze through instructions that propagate but don't produce
   // poison as far as possible. If an operand of freeze follows three
-  // conditions 1) one-use, and 2) does not produce poison then push
+  // conditions 1) one-use, 2) does not produce poison, and 3) has all but one
+  // guaranteed-non-poison operands (or is a BUILD_VECTOR or similar) then push
   // the freeze through to the operands that are not guaranteed non-poison.
   // NOTE: we will strip poison-generating flags, so ignore them here.
   if (DAG.canCreateUndefOrPoison(N0, /*PoisonOnly*/ false,
@@ -16725,6 +16726,18 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
       N0->getNumValues() != 1 || !N0->hasOneUse())
     return SDValue();
 
+  // TOOD: we should always allow multiple operands, however this increases the
+  // likelihood of infinite loops due to the ReplaceAllUsesOfValueWith call
+  // below causing later nodes that share frozen operands to fold again and no
+  // longer being able to confirm other operands are not poison due to recursion
+  // depth limits on isGuaranteedNotToBeUndefOrPoison.
+  bool AllowMultipleMaybePoisonOperands =
+      N0.getOpcode() == ISD::SELECT_CC || N0.getOpcode() == ISD::SETCC ||
+      N0.getOpcode() == ISD::BUILD_VECTOR ||
+      N0.getOpcode() == ISD::BUILD_PAIR ||
+      N0.getOpcode() == ISD::VECTOR_SHUFFLE ||
+      N0.getOpcode() == ISD::CONCAT_VECTORS || N0.getOpcode() == ISD::FMUL;
+
   // Avoid turning a BUILD_VECTOR that can be recognized as "all zeros", "all
   // ones" or "constant" into something that depends on FrozenUndef. We can
   // instead pick undef values to keep those properties, while at the same time
@@ -16757,6 +16770,10 @@ SDValue DAGCombiner::visitFREEZE(SDNode *N) {
       MaybePoisonOperandNumbers.push_back(OpNo);
     if (!HadMaybePoisonOperands)
       continue;
+    if (IsNewMaybePoisonOperand && !AllowMultipleMaybePoisonOperands) {
+      // Multiple maybe-poison ops when not allowed - bail out.
+      return SDValue();
+    }
   }
   // NOTE: the whole op may be not guaranteed to not be undef or poison because
   // it could create undef or poison due to it's poison-generating flags.
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index e0597988e8907..37fddcf943681 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -778,7 +778,7 @@ SDValue TargetLowering::SimplifyMultipleUseDemandedBits(
   case ISD::FREEZE: {
     SDValue N0 = Op.getOperand(0);
     if (DAG.isGuaranteedNotToBeUndefOrPoison(N0, DemandedElts,
-                                             /*PoisonOnly=*/false))
+                                             /*PoisonOnly=*/false, Depth + 1))
       return N0;
     break;
   }
@@ -3369,7 +3369,8 @@ bool TargetLowering::SimplifyDemandedVectorElts(
   case ISD::FREEZE: {
     SDValue N0 = Op.getOperand(0);
     if (TLO.DAG.isGuaranteedNotToBeUndefOrPoison(N0, DemandedElts,
-                                                 /*PoisonOnly=*/false))
+                                                 /*PoisonOnly=*/false,
+                                                 Depth + 1))
       return TLO.CombineTo(Op, N0);
 
     // TODO: Replace this with the general fold from DAGCombiner::visitFREEZE
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 5e35d5630d667..d755c7e9bf3b3 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -45096,27 +45096,34 @@ bool X86TargetLowering::canCreateUndefOrPoisonForTargetNode(
     bool PoisonOnly, bool ConsiderFlags, unsigned Depth) const {
 
   switch (Op.getOpcode()) {
+  // SSE vector insert/extracts use modulo indices.
+  case X86ISD::PINSRB:
+  case X86ISD::PINSRW:
+  case X86ISD::PEXTRB:
+  case X86ISD::PEXTRW:
+    return false;
   // SSE vector multiplies are either inbounds or saturate.
   case X86ISD::VPMADDUBSW:
   case X86ISD::VPMADDWD:
+    return false;
   // SSE vector shifts handle out of bounds shift amounts.
   case X86ISD::VSHLI:
   case X86ISD::VSRLI:
   case X86ISD::VSRAI:
     return false;
-    // SSE blends.
+  // SSE blends.
   case X86ISD::BLENDI:
   case X86ISD::BLENDV:
     return false;
-    // SSE target shuffles.
+  // SSE target shuffles.
   case X86ISD::PSHUFD:
   case X86ISD::UNPCKL:
   case X86ISD::UNPCKH:
   case X86ISD::VPERMILPI:
   case X86ISD::VPERMV3:
     return false;
-    // SSE comparisons handle all icmp/fcmp cases.
-    // TODO: Add CMPM/MM with test coverage.
+  // SSE comparisons handle all icmp/fcmp cases.
+  // TODO: Add CMPM/MM with test coverage.
   case X86ISD::CMPP:
   case X86ISD::PCMPEQ:
   case X86ISD::PCMPGT:
diff --git a/llvm/test/CodeGen/AMDGPU/div_i128.ll b/llvm/test/CodeGen/AMDGPU/div_i128.ll
index f8e13fcdd2273..51398a45055eb 100644
--- a/llvm/test/CodeGen/AMDGPU/div_i128.ll
+++ b/llvm/test/CodeGen/AMDGPU/div_i128.ll
@@ -475,28 +475,21 @@ define i128 @v_sdiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -507,7 +500,6 @@ define i128 @v_sdiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -1043,10 +1035,10 @@ define i128 @v_sdiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    s_mov_b64 s[6:7], 1
 ; GFX9-O0-NEXT:    s_mov_b32 s5, s6
 ; GFX9-O0-NEXT:    s_waitcnt vmcnt(1)
@@ -2664,28 +2656,21 @@ define i128 @v_udiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -2696,7 +2681,6 @@ define i128 @v_udiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -3232,10 +3216,10 @@ define i128 @v_udiv_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    s_mov_b64 s[6:7], 1
 ; GFX9-O0-NEXT:    s_mov_b32 s5, s6
 ; GFX9-O0-NEXT:    s_waitcnt vmcnt(1)
diff --git a/llvm/test/CodeGen/AMDGPU/rem_i128.ll b/llvm/test/CodeGen/AMDGPU/rem_i128.ll
index ba9dd8f7c2468..6512bee36e88b 100644
--- a/llvm/test/CodeGen/AMDGPU/rem_i128.ll
+++ b/llvm/test/CodeGen/AMDGPU/rem_i128.ll
@@ -513,28 +513,21 @@ define i128 @v_srem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -545,7 +538,6 @@ define i128 @v_srem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -1081,10 +1073,10 @@ define i128 @v_srem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:20 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v5, off, s[0:3], s32 offset:24 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v0, off, s[0:3], s32 offset:28 ; 4-byte Folded Reload
+; GFX9-O0-NEXT:    buffer_load_dword v1, off, s[0:3], s32 offset:32 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    s_mov_b64 s[6:7], 1
 ; GFX9-O0-NEXT:    s_mov_b32 s5, s6
 ; GFX9-O0-NEXT:    s_waitcnt vmcnt(1)
@@ -1897,28 +1889,21 @@ define i128 @v_urem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v5, v8
+; GFX9-O0-NEXT:    buffer_store_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    s_nop 0
+; GFX9-O0-NEXT:    buffer_store_dword v5, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; implicit-def: $sgpr8
 ; GFX9-O0-NEXT:    ; kill: def $vgpr7 killed $vgpr7 def $vgpr7_vgpr8 killed $exec
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v8, v6
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v8
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v7
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:28 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:32 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    v_mov_b32_e32 v10, v5
-; GFX9-O0-NEXT:    v_mov_b32_e32 v9, v4
-; GFX9-O0-NEXT:    buffer_store_dword v9, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    buffer_store_dword v7, off, s[0:3], s32 offset:20 ; 4-byte Folded Spill
 ; GFX9-O0-NEXT:    s_nop 0
-; GFX9-O0-NEXT:    buffer_store_dword v10, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
-; GFX9-O0-NEXT:    s_mov_b64 s[8:9], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[8:9]
+; GFX9-O0-NEXT:    buffer_store_dword v8, off, s[0:3], s32 offset:24 ; 4-byte Folded Spill
+; GFX9-O0-NEXT:    v_cmp_eq_u64_e64 s[8:9], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    s_mov_b64 s[12:13], 0x7f
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[12:13]
-; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_gt_u64_e64 s[14:15], v[4:5], s[12:13]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v9, 0, 1, s[14:15]
-; GFX9-O0-NEXT:    s_mov_b64 s[14:15], s[6:7]
-; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[14:15]
+; GFX9-O0-NEXT:    v_cmp_ne_u64_e64 s[14:15], v[7:8], s[6:7]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, 0, 1, s[14:15]
 ; GFX9-O0-NEXT:    v_cndmask_b32_e64 v6, v6, v9, s[8:9]
 ; GFX9-O0-NEXT:    v_and_b32_e64 v6, 1, v6
@@ -1929,7 +1914,6 @@ define i128 @v_urem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    v_mov_b32_e32 v6, v5
 ; GFX9-O0-NEXT:    s_mov_b32 s14, s13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v6, v6, s14
-; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 killed $vgpr4_vgpr5 killed $exec
 ; GFX9-O0-NEXT:    ; kill: def $sgpr12 killed $sgpr12 killed $sgpr12_sgpr13
 ; GFX9-O0-NEXT:    v_xor_b32_e64 v4, v4, s12
 ; GFX9-O0-NEXT:    ; kill: def $vgpr4 killed $vgpr4 def $vgpr4_vgpr5 killed $exec
@@ -2465,10 +2449,10 @@ define i128 @v_urem_i128_vv(i128 %lhs, i128 %rhs) {
 ; GFX9-O0-NEXT:    buffer_load_dword v7, off, s[0:3], s32 offset:40 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v10, off, s[0:3], s32 offset:44 ; 4-byte Folded Reload
 ; GFX9-O0-NEXT:    buffer_load_dword v11, off, s[0:3], s32 offset:48 ; 4-byte Folded Reload
-; GFX9-O0-NEXT:    buffer_load_dword v4, off, s[0:3], s32 offset:28 ; 4-byte Folded...
[truncated]

@RKSimon RKSimon mentioned this pull request Jul 24, 2025
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@RKSimon RKSimon requested review from nikic, phoebewang and bjope July 25, 2025 07:37
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nikic commented Jul 25, 2025

Do we need all of those? For the release branch, can we revert the change fully? Or is other stuff already based on it?

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RKSimon commented Jul 25, 2025

a612be6 I just included as it simplified the merge (it gets added back again later as part of the revert)

4f07800 would be the easiest to remove

@RKSimon RKSimon changed the title [DAG] visitFREEZE - limit freezing of multiple operands release/21.x: [DAG] visitFREEZE - limit freezing of multiple operands Jul 28, 2025
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RKSimon commented Jul 28, 2025

I'll rebase with fewer patches once #150746 has landed - its going to be a mess anyhow

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RKSimon commented Aug 1, 2025

ping

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nikic approved these changes Aug 1, 2025
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LGTM, though I'd probably squash the first two commits. The back and forth is confusing.

RKSimon added 2 commits August 1, 2025 17:19
@RKSimon
[DAG] visitFREEZE - limit freezing of multiple operands (llvm#149797)
8a52605 
This is a partial revert of llvm#145939 (I've kept the BUILD_VECTOR(FREEZE(UNDEF), FREEZE(UNDEF), elt2, ...) canonicalization) as we're getting reports of infinite loops (llvm#148084).

The issue appears to be due to deep chains of nodes and how visitFREEZE replaces all instances of an operand with a common frozen version - other users of the original frozen node then get added back to the worklist but might no longer be able to confirm a node isn't poison due to recursion depth limits on isGuaranteedNotToBeUndefOrPoison.

The issue still exists with the old implementation but by only allowing a single frozen operand it helps prevent cases of interdependent frozen nodes.

I'm still working on supporting multiple operands as its critical for topological DAG handling but need to get a fix in for trunk and 21.x.

Fixes llvm#148084
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[RISCV] Add test coverage for llvm#148084
d306600
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RKSimon commented Aug 2, 2025

@tru This should be OK to merge now - thanks.

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@nikic nikic nikic approved these changes

@phoebewang phoebewang Awaiting requested review from phoebewang

@bjope bjope Awaiting requested review from bjope

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