[llvm] [RISCV] Move RISCVInsertVSETVLI to after phi elimination (PR #91440)

[Luke Lau via llvm-commits]

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@@ -541,9 +541,16 @@ void RISCVPassConfig::addPreRegAlloc() {
   addPass(createRISCVPreRAExpandPseudoPass());
   if (TM->getOptLevel() != CodeGenOptLevel::None)
     addPass(createRISCVMergeBaseOffsetOptPass());
+
   addPass(createRISCVInsertReadWriteCSRPass());
   addPass(createRISCVInsertWriteVXRMPass());
-  addPass(createRISCVInsertVSETVLIPass());
+
+  // Run RISCVInsertVSETVLI after PHI elimination. On O1 and above do it after
+  // register coalescing so needVSETVLIPHI doesn't need to look through COPYs.
+  if (TM->getOptLevel() == CodeGenOptLevel::None)
+    insertPass(&PHIEliminationID, createRISCVInsertVSETVLIPass());
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lukel97 wrote:

Should be fixed in #92303 

https://github.com/llvm/llvm-project/pull/91440