[llvm] [RISCV] Move performCombineVMergeAndVOps into RISCVFoldMasks (PR #71764)

[Luke Lau via llvm-commits]

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@@ -9,15 +9,29 @@
 // This pass performs various peephole optimisations that fold masks into vector
 // pseudo instructions after instruction selection.
 //
-// Currently it converts
-// PseudoVMERGE_VVM %false, %false, %true, %allonesmask, %vl, %sew
+// It performs the following transforms:
+//
+// %true = PseudoFOO %passthru, ..., %vl, %sew
+// %x = PseudoVMERGE_VVM %passthru, %passthru, %true, %mask, %vl, %sew
+// ->
+// %x = PseudoFOO_MASK %false, ..., %mask, %vl, %sew
+//
+// %x = PseudoFOO_MASK ..., %allonesmask, %vl, %sew
 // ->
-// PseudoVMV_V_V %false, %true, %vl, %sew
+// %x = PseudoFOO ..., %vl, %sew
+//
+// %x = PseudoVMERGE_VVM %false, %false, %true, %allonesmask, %vl, %sew
+// ->
+// %x = PseudoVMV_V_V %false, %true, %vl, %sew
 //
 //===---------------------------------------------------------------------===//
 
 #include "RISCV.h"
+#include "RISCVISelDAGToDAG.h"
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lukel97 wrote:

We need RISCVISelDAGToDAG.h since that's where the RISCVMaskedPseudos table is defined, and it's still used by doPeepholeMaskedRVC. The next and final patch in this series would move the table to over to RISCVFoldMasks.cpp

https://github.com/llvm/llvm-project/pull/71764