[llvm] [AMDGPU] Make dead SGPR to not depend on exec in `isIgnorableUse` (PR #218942)

[Jay Foad via llvm-commits]

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@@ -267,10 +267,10 @@ bool SIInstrInfo::resultDependsOnExec(const MachineInstr &MI) const {
   if (MI.isConvergent())
     return true;
 
-  // If it defines SGPR it depends on EXEC
+  // If it defines an SGPR it depends on EXEC, unless it's dead.
   const MachineRegisterInfo &MRI = MI.getMF()->getRegInfo();
   for (const MachineOperand &Def : MI.defs()) {
-    if (!Def.isReg())
+    if (!Def.isReg() || Def.isDead())
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jayfoad wrote:

All `defs` are registers so you can remove that part of the check.

https://github.com/llvm/llvm-project/pull/218942