[PATCH] D98888: [AMDGPU] SIOptimizeExecMaskingPreRA should check constant bus constraint when folds EXEC copy

[Alexander via Phabricator via llvm-commits]

alex-t created this revision.
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Herald added subscribers: kerbowa, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, jvesely, kzhuravl, arsenm.
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Folding EXEC copy into it's single use may lead to constant bus constraint violation as it adds one more SGPR operand.

  This change makes it validate the user instruction with the new SGPR operand and only fold it if it is legal.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D98888

Files:
  llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp


Index: llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
+++ llvm/lib/Target/AMDGPU/SIOptimizeExecMaskingPreRA.cpp
@@ -416,15 +416,19 @@
         continue;
 
       Register SavedExec = I->getOperand(0).getReg();
-      if (SavedExec.isVirtual() && MRI->hasOneNonDBGUse(SavedExec) &&
-          MRI->use_instr_nodbg_begin(SavedExec)->getParent() ==
-              I->getParent()) {
-        LLVM_DEBUG(dbgs() << "Redundant EXEC COPY: " << *I << '\n');
-        LIS->RemoveMachineInstrFromMaps(*I);
-        I->eraseFromParent();
-        MRI->replaceRegWith(SavedExec, ExecReg);
-        LIS->removeInterval(SavedExec);
-        Changed = true;
+      if (SavedExec.isVirtual() && MRI->hasOneNonDBGUse(SavedExec)) {
+        MachineInstr *SingleExecUser = &*MRI->use_instr_nodbg_begin(SavedExec);
+        int idx = SingleExecUser->findRegisterUseOperandIdx(SavedExec);
+        assert(idx != -1);
+        if (SingleExecUser->getParent() == I->getParent() &&
+            TII->isOperandLegal(*SingleExecUser, idx, &I->getOperand(1))) {
+          LLVM_DEBUG(dbgs() << "Redundant EXEC COPY: " << *I << '\n');
+          LIS->RemoveMachineInstrFromMaps(*I);
+          I->eraseFromParent();
+          MRI->replaceRegWith(SavedExec, ExecReg);
+          LIS->removeInterval(SavedExec);
+          Changed = true;
+        }
       }
       break;
     }


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