[DAG][ARM] computeKnownBitsForTargetNode - add handling for ARMISD VORRIMM\VBICIMM nodes

[woruyu]

Summary

This PR resolves #147179

[llvmbot]

@llvm/pr-subscribers-backend-arm

Author: woruyu (woruyu)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/149494.diff

1 Files Affected:

• (modified) llvm/lib/Target/ARM/ARMISelLowering.cpp (+25)

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index fd3b0525c1056..e9ec35fa1dd8c 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -20106,6 +20106,31 @@ void ARMTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
     Known = KnownOp0.intersectWith(KnownOp1);
     break;
   }
+  case ARMISD::VORRIMM: {
+    KnownBits KnownLHS = DAG.computeKnownBits(Op.getOperand(0), Depth + 1);
+
+    unsigned Encoded = Op.getConstantOperandVal(1);
+    unsigned ElemSize = Op.getValueType().getScalarSizeInBits();
+    uint64_t DecodedVal = ARM_AM::decodeVMOVModImm(Encoded, ElemSize);
+    APInt Imm(Known.getBitWidth(), DecodedVal);
+
+    Known.One = KnownLHS.One | Imm;
+    Known.Zero = KnownLHS.Zero & ~Imm;
+    return;
+  }
+  case ARMISD::VBICIMM: {
+    KnownBits KnownLHS = DAG.computeKnownBits(Op.getOperand(0), Depth + 1);
+
+    unsigned Encoded = Op.getConstantOperandVal(1);
+    unsigned ElemSize = Op.getValueType().getScalarSizeInBits();
+    uint64_t DecodedVal = ARM_AM::decodeVMOVModImm(Encoded, ElemSize);
+    APInt Imm(Known.getBitWidth(), DecodedVal);
+
+    APInt NotImm = ~Imm;
+    Known.One = KnownLHS.One & NotImm;
+    Known.Zero = KnownLHS.Zero | Imm;
+    return;
+  }
   }
 }
 

[RKSimon]

Test coverage? Some of the ARM experts may have some suggestions.

[davemgreen]

Finding the tests for this is often difficult. Is it worth adding a test like AArch64SelectionDAGTest for them?