[llvm] fc2b4df - [DAGCombiner] Add use check for VSCALE in visitSUB.

[via llvm-commits]

Author: wanglian
Date: 2022-08-19T09:46:18+08:00
New Revision: fc2b4dfef2f1c4d04d0d5d25e14ffaa0622d5189

URL: https://github.com/llvm/llvm-project/commit/fc2b4dfef2f1c4d04d0d5d25e14ffaa0622d5189
DIFF: https://github.com/llvm/llvm-project/commit/fc2b4dfef2f1c4d04d0d5d25e14ffaa0622d5189.diff

LOG: [DAGCombiner] Add use check for VSCALE in visitSUB.

Reviewed By: david-arm

Differential Revision: https://reviews.llvm.org/D132115

Added: 
    

Modified: 
    llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/test/CodeGen/AArch64/sve-vscale-combine.ll

Removed: 
    


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diff  --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 56beea3e248ae..11fb6fe1c165e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3720,7 +3720,7 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
   }
 
   // canonicalize (sub X, (vscale * C)) to (add X, (vscale * -C))
-  if (N1.getOpcode() == ISD::VSCALE) {
+  if (N1.getOpcode() == ISD::VSCALE && N1.hasOneUse()) {
     const APInt &IntVal = N1.getConstantOperandAPInt(0);
     return DAG.getNode(ISD::ADD, DL, VT, N0, DAG.getVScale(DL, VT, -IntVal));
   }

diff  --git a/llvm/test/CodeGen/AArch64/sve-vscale-combine.ll b/llvm/test/CodeGen/AArch64/sve-vscale-combine.ll
index 1ebe91f329b38..9306c208c3b55 100644
--- a/llvm/test/CodeGen/AArch64/sve-vscale-combine.ll
+++ b/llvm/test/CodeGen/AArch64/sve-vscale-combine.ll
@@ -76,10 +76,8 @@ define i32 @combine_sub_vscale_i32(i32 %in) nounwind {
 define i64 @multiple_uses_sub_vscale_i64(i64 %x, i64 %y) nounwind {
 ; CHECK-LABEL: multiple_uses_sub_vscale_i64:
 ; CHECK-NEXT:  rdvl	x8, #1
-; CHECK-NEXT:  rdvl	x9, #-1
 ; CHECK-NEXT:  lsr	x8, x8, #4
-; CHECK-NEXT:  asr	x9, x9, #4
-; CHECK-NEXT:  add	x9, x0, x9
+; CHECK-NEXT:  sub	x9, x0, x8
 ; CHECK-NEXT:  add	x8, x1, x8
 ; CHECK-NEXT:  mul	x0, x9, x8
 ; CHECK-NEXT:  ret