[llvm] AArch64/GlobalISel: Mark the MOPS pseudo NZCV def dead (PR #227643)

[via llvm-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

AArch64/GlobalISel: Mark the MOPS pseudo NZCV def dead

Co-authored-by: Claude Opus 5 <noreply@<!-- -->anthropic.com>

Remove test

---
Full diff: https://github.com/llvm/llvm-project/pull/227643.diff


1 Files Affected:

- (modified) llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp (+5-2) 


``````````diff
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
index 22c0e3a3a462d..96f932e71dbd0 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
@@ -3665,11 +3665,13 @@ bool AArch64InstructionSelector::selectMOPS(MachineInstr &GI,
   Register DefSize = MRI.createVirtualRegister(&AArch64::GPR64RegClass);
   if (IsSet) {
     MIB.buildInstr(Mopcode, {DefDstPtr, DefSize},
-                   {DstPtrCopy, SizeCopy, SrcValCopy});
+                   {DstPtrCopy, SizeCopy, SrcValCopy})
+        .setOperandDead(5); // implicit-def $nzcv
   } else {
     Register DefSrcPtr = MRI.createVirtualRegister(&SrcValRegClass);
     MIB.buildInstr(Mopcode, {DefDstPtr, DefSrcPtr, DefSize},
-                   {DstPtrCopy, SrcValCopy, SizeCopy});
+                   {DstPtrCopy, SrcValCopy, SizeCopy})
+        .setOperandDead(6); // implicit-def $nzcv
   }
 
   GI.eraseFromParent();
@@ -6854,6 +6856,7 @@ bool AArch64InstructionSelector::selectIntrinsicWithSideEffects(
     auto Memset = MIB.buildInstr(AArch64::MOPSMemorySetTaggingPseudo,
                                  {DstDef, SizeDef}, {DstUse, SizeUse, ValUse});
     Memset.cloneMemRefs(I);
+    Memset.setOperandDead(5); // implicit-def $nzcv
     constrainSelectedInstRegOperands(*Memset, TII, TRI, RBI);
     break;
   }

``````````

</details>


https://github.com/llvm/llvm-project/pull/227643