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[X86] Don't invert NewCC variable while processing the jcc/setcc/cmovcc instructions in optimizeCompareInstr. 

The NewCC variable is calculated outside of the loop that processes jcc/setcc/cmovcc instructions. If we invert it during the loop it can cause an incorrect value to be used by a later iteration. Instead only read it during the loop and use a new variable to store the possibly inverted value.

Fixes PR35399.

llvm-svn: 318934
This commit is contained in:
Craig Topper 2017-11-23 19:25:45 +00:00
parent f31b0b850b
commit 40a1edc307
2 changed files with 31 additions and 7 deletions
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16
llvm/lib/Target/X86/X86InstrInfo.cpp
View File

@ -7475,6 +7475,7 @@ bool X86InstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
} }
if (OldCC == X86::COND_INVALID) return false; if (OldCC == X86::COND_INVALID) return false;
} }
X86::CondCode ReplacementCC = X86::COND_INVALID;
if (IsCmpZero) { if (IsCmpZero) {
switch (OldCC) { switch (OldCC) {
default: break; default: break;
@ -7494,31 +7495,32 @@ bool X86InstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
default: default:
return false; return false;
case X86::COND_E: case X86::COND_E:
ReplacementCC = NewCC;
break; break;
case X86::COND_NE: case X86::COND_NE:
NewCC = GetOppositeBranchCondition(NewCC); ReplacementCC = GetOppositeBranchCondition(NewCC);
break; break;
} }
} else if (IsSwapped) { } else if (IsSwapped) {
// If we have SUB(r1, r2) and CMP(r2, r1), the condition code needs // If we have SUB(r1, r2) and CMP(r2, r1), the condition code needs
// to be changed from r2 > r1 to r1 < r2, from r2 < r1 to r1 > r2, etc. // to be changed from r2 > r1 to r1 < r2, from r2 < r1 to r1 > r2, etc.
// We swap the condition code and synthesize the new opcode. // We swap the condition code and synthesize the new opcode.
NewCC = getSwappedCondition(OldCC); ReplacementCC = getSwappedCondition(OldCC);
if (NewCC == X86::COND_INVALID) return false; if (ReplacementCC == X86::COND_INVALID) return false;
} }
if ((ShouldUpdateCC || IsSwapped) && NewCC != OldCC) { if ((ShouldUpdateCC || IsSwapped) && ReplacementCC != OldCC) {
// Synthesize the new opcode. // Synthesize the new opcode.
bool HasMemoryOperand = Instr.hasOneMemOperand(); bool HasMemoryOperand = Instr.hasOneMemOperand();
unsigned NewOpc; unsigned NewOpc;
if (Instr.isBranch()) if (Instr.isBranch())
NewOpc = GetCondBranchFromCond(NewCC); NewOpc = GetCondBranchFromCond(ReplacementCC);
else if(OpcIsSET) else if(OpcIsSET)
NewOpc = getSETFromCond(NewCC, HasMemoryOperand); NewOpc = getSETFromCond(ReplacementCC, HasMemoryOperand);
else { else {
unsigned DstReg = Instr.getOperand(0).getReg(); unsigned DstReg = Instr.getOperand(0).getReg();
const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg); const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg);
NewOpc = getCMovFromCond(NewCC, TRI->getRegSizeInBits(*DstRC)/8, NewOpc = getCMovFromCond(ReplacementCC, TRI->getRegSizeInBits(*DstRC)/8,
HasMemoryOperand); HasMemoryOperand);
} }

22
llvm/test/CodeGen/X86/pr35399.ll Normal file
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@ -0,0 +1,22 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-unknown -mattr=lzcnt | FileCheck %s
; Make sure we emit opoosite setcc instructions.
define i64 @pr35399(i64, i8*, i8*) {
; CHECK-LABEL: pr35399:
; CHECK: # BB#0:
; CHECK-NEXT: lzcntq %rdi, %rax
; CHECK-NEXT: setae (%rsi)
; CHECK-NEXT: setb (%rdx)
; CHECK-NEXT: retq
%4 = tail call i64 @llvm.ctlz.i64(i64 %0, i1 false)
%5 = icmp ne i64 %0, 0
%6 = zext i1 %5 to i8
store i8 %6, i8* %1, align 1
%7 = xor i1 %5, true
%8 = zext i1 %7 to i8
store i8 %8, i8* %2, align 1
ret i64 %4
}
declare i64 @llvm.ctlz.i64(i64, i1)