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[X86] Try to shrink i64 compares if the input has enough one bits #149719

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[X86] Try to shrink i64 compares if the input has enough one bits #149719

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44e4397
Pre-commit test (NFC)
AZero13 Jul 20, 2025
3395955
[X86] Try to shrink signed i64 compares if the input has enough one bits
AZero13 Jul 20, 2025
7755719
Comments
AZero13 Jul 20, 2025
7eee49b
Use ComputeNumSignBits > 32
AZero13 Jul 20, 2025
0c2b42c
Address concerns
AZero13 Jul 23, 2025
bdc83c2
Improve comment
AZero13 Jul 23, 2025
67f9a5c
Add isX86CCUnsigned
AZero13 Jul 26, 2025
c8bb79a
Fix error
AZero13 Jul 27, 2025
28cef73
Remove unsigned check
AZero13 Jul 27, 2025
5631b13
Add new tests for eq and unsigned checks
AZero13 Jul 27, 2025
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11 changes: 10 additions & 1 deletion llvm/lib/Target/X86/X86ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -23479,7 +23479,6 @@ static SDValue EmitCmp(SDValue Op0, SDValue Op1, X86::CondCode X86CC,
}

// Try to shrink i64 compares if the input has enough zero bits.
// TODO: Add sign-bits equivalent for isX86CCSigned(X86CC)?
if (CmpVT == MVT::i64 && !isX86CCSigned(X86CC) &&
Op0.hasOneUse() && // Hacky way to not break CSE opportunities with sub.
DAG.MaskedValueIsZero(Op1, APInt::getHighBitsSet(64, 32)) &&
Expand All @@ -23489,6 +23488,16 @@ static SDValue EmitCmp(SDValue Op0, SDValue Op1, X86::CondCode X86CC,
Op1 = DAG.getNode(ISD::TRUNCATE, dl, CmpVT, Op1);
}

// Try to shrink all i64 compares if the inputs are representable as signed
// i32.
if (CmpVT == MVT::i64 &&
Op0.hasOneUse() && // Hacky way to not break CSE opportunities with sub.
DAG.ComputeNumSignBits(Op1) > 32 && DAG.ComputeNumSignBits(Op0) > 32) {
CmpVT = MVT::i32;
Op0 = DAG.getNode(ISD::TRUNCATE, dl, CmpVT, Op0);
Op1 = DAG.getNode(ISD::TRUNCATE, dl, CmpVT, Op1);
}

// 0-x == y --> x+y == 0
// 0-x != y --> x+y != 0
if (Op0.getOpcode() == ISD::SUB && isNullConstant(Op0.getOperand(0)) &&
Expand Down
182 changes: 182 additions & 0 deletions llvm/test/CodeGen/X86/cmp.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -956,3 +956,185 @@ define i1 @fold_test_and_with_chain(ptr %x, ptr %y, i32 %z) {
store i32 %z, ptr %y
ret i1 %c
}

define i1 @sext_mask(i32 %a) {
; CHECK-LABEL: sext_mask:
; CHECK: # %bb.0:
; CHECK-NEXT: cmpl $-523, %edi # encoding: [0x81,0xff,0xf5,0xfd,0xff,0xff]
; CHECK-NEXT: # imm = 0xFDF5
; CHECK-NEXT: setl %al # encoding: [0x0f,0x9c,0xc0]
; CHECK-NEXT: retq # encoding: [0xc3]
%a64 = sext i32 %a to i64
%v1 = icmp slt i64 %a64, -523
ret i1 %v1
}

define i1 @sext_i9_mask(i9 %a) {
; NO-NDD-LABEL: sext_i9_mask:
; NO-NDD: # %bb.0:
; NO-NDD-NEXT: # kill: def $edi killed $edi def $rdi
; NO-NDD-NEXT: shlq $55, %rdi # encoding: [0x48,0xc1,0xe7,0x37]
; NO-NDD-NEXT: sarq $55, %rdi # encoding: [0x48,0xc1,0xff,0x37]
; NO-NDD-NEXT: cmpl $-522, %edi # encoding: [0x81,0xff,0xf6,0xfd,0xff,0xff]
; NO-NDD-NEXT: # imm = 0xFDF6
; NO-NDD-NEXT: setl %al # encoding: [0x0f,0x9c,0xc0]
; NO-NDD-NEXT: retq # encoding: [0xc3]
;
; NDD-LABEL: sext_i9_mask:
; NDD: # %bb.0:
; NDD-NEXT: # kill: def $edi killed $edi def $rdi
; NDD-NEXT: shlq $55, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xe7,0x37]
; NDD-NEXT: sarq $55, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xff,0x37]
; NDD-NEXT: cmpl $-522, %edi # encoding: [0x81,0xff,0xf6,0xfd,0xff,0xff]
; NDD-NEXT: # imm = 0xFDF6
; NDD-NEXT: setl %al # encoding: [0x0f,0x9c,0xc0]
; NDD-NEXT: retq # encoding: [0xc3]
%a64 = sext i9 %a to i64
%v1 = icmp slt i64 %a64, -522
ret i1 %v1
}

define i1 @sext_i32_mask(i32 %a) {
; CHECK-LABEL: sext_i32_mask:
; CHECK: # %bb.0:
; CHECK-NEXT: cmpl $-522, %edi # encoding: [0x81,0xff,0xf6,0xfd,0xff,0xff]
; CHECK-NEXT: # imm = 0xFDF6
; CHECK-NEXT: setl %al # encoding: [0x0f,0x9c,0xc0]
; CHECK-NEXT: retq # encoding: [0xc3]
%a64 = sext i32 %a to i64
%v1 = icmp slt i64 %a64, -522
ret i1 %v1
}

define i1 @i40(i40 %a) {
; NO-NDD-LABEL: i40:
; NO-NDD: # %bb.0:
; NO-NDD-NEXT: shlq $24, %rdi # encoding: [0x48,0xc1,0xe7,0x18]
; NO-NDD-NEXT: sarq $24, %rdi # encoding: [0x48,0xc1,0xff,0x18]
; NO-NDD-NEXT: cmpq $-521, %rdi # encoding: [0x48,0x81,0xff,0xf7,0xfd,0xff,0xff]
; NO-NDD-NEXT: # imm = 0xFDF7
; NO-NDD-NEXT: setl %al # encoding: [0x0f,0x9c,0xc0]
; NO-NDD-NEXT: retq # encoding: [0xc3]
;
; NDD-LABEL: i40:
; NDD: # %bb.0:
; NDD-NEXT: shlq $24, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xe7,0x18]
; NDD-NEXT: sarq $24, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xff,0x18]
; NDD-NEXT: cmpq $-521, %rdi # encoding: [0x48,0x81,0xff,0xf7,0xfd,0xff,0xff]
; NDD-NEXT: # imm = 0xFDF7
; NDD-NEXT: setl %al # encoding: [0x0f,0x9c,0xc0]
; NDD-NEXT: retq # encoding: [0xc3]
%a64 = sext i40 %a to i64
%v1 = icmp slt i64 %a64, -521
ret i1 %v1
}

define i1 @sext_i9_mask_sgt(i9 %a) {
; NO-NDD-LABEL: sext_i9_mask_sgt:
; NO-NDD: # %bb.0:
; NO-NDD-NEXT: # kill: def $edi killed $edi def $rdi
; NO-NDD-NEXT: shlq $55, %rdi # encoding: [0x48,0xc1,0xe7,0x37]
; NO-NDD-NEXT: sarq $55, %rdi # encoding: [0x48,0xc1,0xff,0x37]
; NO-NDD-NEXT: cmpl $-520, %edi # encoding: [0x81,0xff,0xf8,0xfd,0xff,0xff]
; NO-NDD-NEXT: # imm = 0xFDF8
; NO-NDD-NEXT: setge %al # encoding: [0x0f,0x9d,0xc0]
; NO-NDD-NEXT: retq # encoding: [0xc3]
;
; NDD-LABEL: sext_i9_mask_sgt:
; NDD: # %bb.0:
; NDD-NEXT: # kill: def $edi killed $edi def $rdi
; NDD-NEXT: shlq $55, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xe7,0x37]
; NDD-NEXT: sarq $55, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xff,0x37]
; NDD-NEXT: cmpl $-520, %edi # encoding: [0x81,0xff,0xf8,0xfd,0xff,0xff]
; NDD-NEXT: # imm = 0xFDF8
; NDD-NEXT: setge %al # encoding: [0x0f,0x9d,0xc0]
; NDD-NEXT: retq # encoding: [0xc3]
%a64 = sext i9 %a to i64
%v1 = icmp sgt i64 %a64, -521
ret i1 %v1
}

define i1 @sext_i32_mask_sgt(i32 %a) {
; CHECK-LABEL: sext_i32_mask_sgt:
; CHECK: # %bb.0:
; CHECK-NEXT: cmpl $-521, %edi # encoding: [0x81,0xff,0xf7,0xfd,0xff,0xff]
; CHECK-NEXT: # imm = 0xFDF7
; CHECK-NEXT: setge %al # encoding: [0x0f,0x9d,0xc0]
; CHECK-NEXT: retq # encoding: [0xc3]
%a64 = sext i32 %a to i64
%v1 = icmp sgt i64 %a64, -522
ret i1 %v1
}

define i1 @i40_sge(i40 %a) {
; NO-NDD-LABEL: i40_sge:
; NO-NDD: # %bb.0:
; NO-NDD-NEXT: shlq $24, %rdi # encoding: [0x48,0xc1,0xe7,0x18]
; NO-NDD-NEXT: sarq $24, %rdi # encoding: [0x48,0xc1,0xff,0x18]
; NO-NDD-NEXT: cmpq $-521, %rdi # encoding: [0x48,0x81,0xff,0xf7,0xfd,0xff,0xff]
; NO-NDD-NEXT: # imm = 0xFDF7
; NO-NDD-NEXT: setge %al # encoding: [0x0f,0x9d,0xc0]
; NO-NDD-NEXT: retq # encoding: [0xc3]
;
; NDD-LABEL: i40_sge:
; NDD: # %bb.0:
; NDD-NEXT: shlq $24, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xe7,0x18]
; NDD-NEXT: sarq $24, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xff,0x18]
; NDD-NEXT: cmpq $-521, %rdi # encoding: [0x48,0x81,0xff,0xf7,0xfd,0xff,0xff]
; NDD-NEXT: # imm = 0xFDF7
; NDD-NEXT: setge %al # encoding: [0x0f,0x9d,0xc0]
; NDD-NEXT: retq # encoding: [0xc3]
%a64 = sext i40 %a to i64
%v1 = icmp sge i64 %a64, -521
ret i1 %v1
}

define i1 @i40_eq(i40 %a) {
; NO-NDD-LABEL: i40_eq:
; NO-NDD: # %bb.0:
; NO-NDD-NEXT: movabsq $1099511627775, %rax # encoding: [0x48,0xb8,0xff,0xff,0xff,0xff,0xff,0x00,0x00,0x00]
; NO-NDD-NEXT: # imm = 0xFFFFFFFFFF
; NO-NDD-NEXT: andq %rdi, %rax # encoding: [0x48,0x21,0xf8]
; NO-NDD-NEXT: movabsq $1099511627255, %rcx # encoding: [0x48,0xb9,0xf7,0xfd,0xff,0xff,0xff,0x00,0x00,0x00]
; NO-NDD-NEXT: # imm = 0xFFFFFFFDF7
; NO-NDD-NEXT: cmpq %rcx, %rax # encoding: [0x48,0x39,0xc8]
; NO-NDD-NEXT: sete %al # encoding: [0x0f,0x94,0xc0]
; NO-NDD-NEXT: retq # encoding: [0xc3]
;
; NDD-LABEL: i40_eq:
; NDD: # %bb.0:
; NDD-NEXT: movabsq $1099511627775, %rax # encoding: [0x48,0xb8,0xff,0xff,0xff,0xff,0xff,0x00,0x00,0x00]
; NDD-NEXT: # imm = 0xFFFFFFFFFF
; NDD-NEXT: andq %rdi, %rax # EVEX TO LEGACY Compression encoding: [0x48,0x21,0xf8]
; NDD-NEXT: movabsq $1099511627255, %rcx # encoding: [0x48,0xb9,0xf7,0xfd,0xff,0xff,0xff,0x00,0x00,0x00]
; NDD-NEXT: # imm = 0xFFFFFFFDF7
; NDD-NEXT: cmpq %rcx, %rax # encoding: [0x48,0x39,0xc8]
; NDD-NEXT: sete %al # encoding: [0x0f,0x94,0xc0]
; NDD-NEXT: retq # encoding: [0xc3]
%a64 = sext i40 %a to i64
%v1 = icmp eq i64 %a64, -521
ret i1 %v1
}

define i1 @i40_ult(i40 %a) {
; NO-NDD-LABEL: i40_ult:
; NO-NDD: # %bb.0:
; NO-NDD-NEXT: shlq $24, %rdi # encoding: [0x48,0xc1,0xe7,0x18]
; NO-NDD-NEXT: sarq $24, %rdi # encoding: [0x48,0xc1,0xff,0x18]
; NO-NDD-NEXT: cmpq $-521, %rdi # encoding: [0x48,0x81,0xff,0xf7,0xfd,0xff,0xff]
; NO-NDD-NEXT: # imm = 0xFDF7
; NO-NDD-NEXT: setb %al # encoding: [0x0f,0x92,0xc0]
; NO-NDD-NEXT: retq # encoding: [0xc3]
;
; NDD-LABEL: i40_ult:
; NDD: # %bb.0:
; NDD-NEXT: shlq $24, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xe7,0x18]
; NDD-NEXT: sarq $24, %rdi # EVEX TO LEGACY Compression encoding: [0x48,0xc1,0xff,0x18]
; NDD-NEXT: cmpq $-521, %rdi # encoding: [0x48,0x81,0xff,0xf7,0xfd,0xff,0xff]
; NDD-NEXT: # imm = 0xFDF7
; NDD-NEXT: setb %al # encoding: [0x0f,0x92,0xc0]
; NDD-NEXT: retq # encoding: [0xc3]
%a64 = sext i40 %a to i64
%v1 = icmp ult i64 %a64, -521
ret i1 %v1
}