[PATCH] D105789: [SelectionDAG] Check use before combining into USUBSAT

[Qiu Chaofan via Phabricator via llvm-commits]

qiucf created this revision.
qiucf added reviewers: RKSimon, craig.topper, efriedma, nemanjai, jsji, PowerPC.
Herald added a subscriber: hiraditya.
qiucf requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

(The test part in this patch is not applicable since it's not pre-committed yet)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D105789

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/PowerPC/sat-add.ll


Index: llvm/test/CodeGen/PowerPC/sat-add.ll
===================================================================
--- llvm/test/CodeGen/PowerPC/sat-add.ll
+++ llvm/test/CodeGen/PowerPC/sat-add.ll
@@ -881,10 +881,8 @@
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    li 5, 4
 ; CHECK-NEXT:    cmpldi 3, 4
-; CHECK-NEXT:    addi 6, 3, -4
 ; CHECK-NEXT:    isellt 5, 3, 5
-; CHECK-NEXT:    cmpld 6, 3
-; CHECK-NEXT:    iselgt 3, 0, 6
+; CHECK-NEXT:    sub 3, 3, 5
 ; CHECK-NEXT:    add 4, 4, 5
 ; CHECK-NEXT:    mulld 3, 3, 4
 ; CHECK-NEXT:    blr
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3209,7 +3209,7 @@
 
   // Try to find umax(a,b) - b or a - umin(a,b) patterns
   // they may be converted to usubsat(a,b).
-  if (Op0.getOpcode() == ISD::UMAX) {
+  if (Op0.getOpcode() == ISD::UMAX && Op0.hasOneUse()) {
     SDValue MaxLHS = Op0.getOperand(0);
     SDValue MaxRHS = Op0.getOperand(1);
     if (MaxLHS == Op1)
@@ -3218,7 +3218,7 @@
       return getTruncatedUSUBSAT(DstVT, SubVT, MaxLHS, Op1, DAG, SDLoc(N));
   }
 
-  if (Op1.getOpcode() == ISD::UMIN) {
+  if (Op1.getOpcode() == ISD::UMIN && Op1.hasOneUse()) {
     SDValue MinLHS = Op1.getOperand(0);
     SDValue MinRHS = Op1.getOperand(1);
     if (MinLHS == Op0)
@@ -3229,7 +3229,8 @@
 
   // sub(a,trunc(umin(zext(a),b))) -> usubsat(a,trunc(umin(b,SatLimit)))
   if (Op1.getOpcode() == ISD::TRUNCATE &&
-      Op1.getOperand(0).getOpcode() == ISD::UMIN) {
+      Op1.getOperand(0).getOpcode() == ISD::UMIN &&
+      Op1.getOperand(0).hasOneUse()) {
     SDValue MinLHS = Op1.getOperand(0).getOperand(0);
     SDValue MinRHS = Op1.getOperand(0).getOperand(1);
     if (MinLHS.getOpcode() == ISD::ZERO_EXTEND && MinLHS.getOperand(0) == Op0)


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