[PATCH] D133469: [X86] Fold SUB(SBB(X,0,W), Y) -> SBB(X,Y,W)

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel.
Herald added subscribers: StephenFan, pengfei, hiraditya.
Herald added a project: All.
craig.topper requested review of this revision.
Herald added a project: LLVM.

Fixes PR57576.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133469

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/pr57576.ll


Index: llvm/test/CodeGen/X86/pr57576.ll
===================================================================
--- llvm/test/CodeGen/X86/pr57576.ll
+++ llvm/test/CodeGen/X86/pr57576.ll
@@ -6,8 +6,7 @@
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    movq %rdi, %rax
 ; CHECK-NEXT:    subq %rdx, %rax
-; CHECK-NEXT:    sbbq $0, %rsi
-; CHECK-NEXT:    subq %rcx, %rsi
+; CHECK-NEXT:    sbbq %rcx, %rsi
 ; CHECK-NEXT:    movq %rsi, %rdx
 ; CHECK-NEXT:    retq
   %5 = zext i64 %1 to i128
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -53951,6 +53951,14 @@
                        Op1.getOperand(0), Op1.getOperand(2));
   }
 
+  // Fold SUB(SBB(X,0,W), Y) -> SBB(X,Y,W)
+  if (Op0.getOpcode() == X86ISD::SBB && Op0->hasOneUse() &&
+      X86::isZeroNode(Op0.getOperand(1))) {
+    assert(!Op0->hasAnyUseOfValue(1) && "Overflow bit in use");
+    return DAG.getNode(X86ISD::SBB, SDLoc(Op1), Op0->getVTList(),
+                       Op0.getOperand(0), Op1, Op0.getOperand(2));
+  }
+
   // Fold SUB(X,SBB(Y,Z,W)) -> SUB(ADC(X,Z,W),Y)
   // Don't fold to ADC(0,0,W)/SETCC_CARRY pattern which will prevent more folds.
   if (Op1.getOpcode() == X86ISD::SBB && Op1->hasOneUse() &&


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D133469.458637.patch
Type: text/x-patch
Size: 1324 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220908/386ff3dd/attachment.bin>