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[x86] simplify cmov with same true/false operands 

llvm-svn: 365998
This commit is contained in:
Sanjay Patel 2019-07-13 12:04:52 +00:00
parent 327db23b66
commit 2097f75eab
2 changed files with 5 additions and 2 deletions
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4
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -36783,6 +36783,10 @@ static SDValue combineCMov(SDNode *N, SelectionDAG &DAG,
X86::CondCode CC = (X86::CondCode)N->getConstantOperandVal(2); X86::CondCode CC = (X86::CondCode)N->getConstantOperandVal(2);
SDValue Cond = N->getOperand(3); SDValue Cond = N->getOperand(3);
// cmov X, X, ?, ? --> X
if (TrueOp == FalseOp)
return TrueOp;
// Try to simplify the EFLAGS and condition code operands. // Try to simplify the EFLAGS and condition code operands.
// We can't always do this as FCMOV only supports a subset of X86 cond. // We can't always do this as FCMOV only supports a subset of X86 cond.
if (SDValue Flags = combineSetCCEFLAGS(Cond, CC, DAG, Subtarget)) { if (SDValue Flags = combineSetCCEFLAGS(Cond, CC, DAG, Subtarget)) {

3
llvm/test/CodeGen/X86/combine-sbb.ll
View File

@ -291,9 +291,8 @@ define i32 @PR40483_sub5(i32*, i32) {
; ;
; X64-LABEL: PR40483_sub5: ; X64-LABEL: PR40483_sub5:
; X64: # %bb.0: ; X64: # %bb.0:
; X64-NEXT: xorl %eax, %eax
; X64-NEXT: subl %esi, (%rdi) ; X64-NEXT: subl %esi, (%rdi)
; X64-NEXT: cmovael %eax, %eax ; X64-NEXT: xorl %eax, %eax
; X64-NEXT: retq ; X64-NEXT: retq
%3 = load i32, i32* %0, align 8 %3 = load i32, i32* %0, align 8
%4 = tail call { i8, i32 } @llvm.x86.subborrow.32(i8 0, i32 %3, i32 %1) %4 = tail call { i8, i32 } @llvm.x86.subborrow.32(i8 0, i32 %3, i32 %1)