[RISCV] Move RISCVInsertVSETVLI::coalesceVSETVLIs back to before insertReadVL

[lukel97]

In #88295 we split out coalesceVSETVLIs (f.k.a doLocalPostpass) into a separate pass, which meant moving it past the call to insertReadVL. Whenever we merged it back in #92869, we left it after insertReadVL. This patch moves it back to its original position.

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

Author: Luke Lau (lukel97)

Changes

In #88295 we split out coalesceVSETVLIs (f.k.a doLocalPostpass) into a separate pass, which meant moving it past the call to insertReadVL. Whenever we merged it back in #92869, we accidentally moved it after insertReadVL. This patch moves it back to its original position.

---

Full diff: https://github.com/llvm/llvm-project/pull/96056.diff

1 Files Affected:

• (modified) llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp (+5-5)

diff --git a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
index d36ce60c24185..877535513c721 100644
--- a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -1813,11 +1813,6 @@ bool RISCVInsertVSETVLI::runOnMachineFunction(MachineFunction &MF) {
   for (MachineBasicBlock &MBB : MF)
     emitVSETVLIs(MBB);
 
-  // Insert PseudoReadVL after VLEFF/VLSEGFF and replace it with the vl output
-  // of VLEFF/VLSEGFF.
-  for (MachineBasicBlock &MBB : MF)
-    insertReadVL(MBB);
-
   // Now that all vsetvlis are explicit, go through and do block local
   // DSE and peephole based demanded fields based transforms.  Note that
   // this *must* be done outside the main dataflow so long as we allow
@@ -1827,6 +1822,11 @@ bool RISCVInsertVSETVLI::runOnMachineFunction(MachineFunction &MF) {
   for (MachineBasicBlock &MBB : MF)
     coalesceVSETVLIs(MBB);
 
+  // Insert PseudoReadVL after VLEFF/VLSEGFF and replace it with the vl output
+  // of VLEFF/VLSEGFF.
+  for (MachineBasicBlock &MBB : MF)
+    insertReadVL(MBB);
+
   BlockInfo.clear();
   return HaveVectorOp;
 }

[wangpc-pp]

LGTM.