From 5e8def2f14151655b0cfdb5d3ad591e3b4771e7d Mon Sep 17 00:00:00 2001
From: Luke Lau <luke@igalia.com>
Date: Wed, 17 Jan 2024 19:29:22 +0700
Subject: [PATCH] Revert "[RISCV] Remove dead early exit in
 performCombineVMergeAndVOps. NFC"

This reverts commit cee60a80101dbc2494865910fc7acef4fcab42bd.

This change is not NFC because there is also an additional check for
isImplicitDef in the branch above.
---
 llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
index df5766a294c982..0d8688ba2eaeaf 100644
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -3545,6 +3545,9 @@ bool RISCVDAGToDAGISel::performCombineVMergeAndVOps(SDNode *N) {
 
   if (IsMasked) {
     assert(HasTiedDest && "Expected tied dest");
+    // The vmerge instruction must be TU.
+    if (isImplicitDef(Merge))
+      return false;
     // The vmerge instruction must have an all 1s mask since we're going to keep
     // the mask from the True instruction.
     // FIXME: Support mask agnostic True instruction which would have an