[llvm] [SIFoldOperands] Folding immediate into a copy invalidates candidates in the fold list (PR #148187)

[Matt Arsenault via llvm-commits]

Juan Manuel Martinez =?utf-8?q?Caamaño?= <juamarti at amd.com>,
Juan Manuel Martinez =?utf-8?q?Caamaño?= <juamarti at amd.com>,
Juan Manuel Martinez =?utf-8?q?Caamaño?= <juamarti at amd.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/148187 at github.com>


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@@ -1785,9 +1787,13 @@ bool SIFoldOperandsImpl::foldInstOperand(MachineInstr &MI,
 
       if (Fold.isImm() && tryConstantFoldOp(Fold.UseMI)) {
         LLVM_DEBUG(dbgs() << "Constant folded " << *Fold.UseMI);
+        // The instruction was folded into a copy, we have to skip any other
+        // occurence of UseMI in the fold list
+        End = std::remove_if(FoldIt + 1, End, [&](const FoldCandidate &F) {
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arsenm wrote:

We really need to rewrite this pass. The fold list is garbage. It would be a lot simpler to just track a map of foldable sources like peephole opt does 

https://github.com/llvm/llvm-project/pull/148187