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AArch64: account for possible frame index operand in compares.

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If the address of a local is used in a comparison, AArch64 can fold the
address-calculation into the comparison via "adds". Unfortunately, a couple of
places (both hit in this one test) are not ready to deal with that yet and just
assume the first source operand is a register.

llvm-svn: 316035
This commit is contained in:
Tim Northover 2017-10-17 21:43:52 +00:00
parent 66256b9583
commit c967f8b495
3 changed files with 28 additions and 0 deletions
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6
lib/Target/AArch64/AArch64InstrInfo.cpp
View File

@ -1038,6 +1038,12 @@ bool AArch64InstrInfo::areMemAccessesTriviallyDisjoint(
bool AArch64InstrInfo::analyzeCompare(const MachineInstr &MI, unsigned &SrcReg, bool AArch64InstrInfo::analyzeCompare(const MachineInstr &MI, unsigned &SrcReg,
unsigned &SrcReg2, int &CmpMask, unsigned &SrcReg2, int &CmpMask,
int &CmpValue) const { int &CmpValue) const {
// The first operand can be a frame index where we'd normally expect a
// register.
assert(MI.getNumOperands() >= 2 && "All AArch64 cmps should have 2 operands");
if (!MI.getOperand(1).isReg())
return false;
switch (MI.getOpcode()) { switch (MI.getOpcode()) {
default: default:
break; break;

3
lib/Target/AArch64/AArch64RedundantCopyElimination.cpp
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@ -201,6 +201,9 @@ bool AArch64RedundantCopyElimination::knownRegValInBlock(
// CMP is an alias for SUBS with a dead destination register. // CMP is an alias for SUBS with a dead destination register.
case AArch64::SUBSWri: case AArch64::SUBSWri:
case AArch64::SUBSXri: { case AArch64::SUBSXri: {
// Sometimes the first operand is a FrameIndex. Bail if tht happens.
if (!PredI.getOperand(1).isReg())
return false;
MCPhysReg DstReg = PredI.getOperand(0).getReg(); MCPhysReg DstReg = PredI.getOperand(0).getReg();
MCPhysReg SrcReg = PredI.getOperand(1).getReg(); MCPhysReg SrcReg = PredI.getOperand(1).getReg();

19
test/CodeGen/AArch64/cmp-frameindex.ll Normal file
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@ -0,0 +1,19 @@
; RUN: llc -mtriple=aarch64 %s -o - | FileCheck %s
; CHECK: test_frameindex_cmp:
; CHECK: cmn sp, #{{[0-9]+}}
define void @test_frameindex_cmp() {
%stack = alloca i8
%stack.int = ptrtoint i8* %stack to i64
%cmp = icmp ne i64 %stack.int, 0
br i1 %cmp, label %bb1, label %bb2
bb1:
call void @bar()
ret void
bb2:
ret void
}
declare void @bar()