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[AArch64][GlobalISel] Use ZExtValue for zext(xor) when invert tb(n)z

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Currently, we use SExtValue to decide whether to invert tbz or tbnz.
However, for the case zext (xor x, c), we should use ZExt rather
than SExt otherwise we will generate totally opposite branches.

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D108755

(cherry picked from commit 5f48c144c58f6d23e850a1978a6fe05887103b17)
This commit is contained in:
guopeilin 2021-09-06 11:11:23 +08:00 committed by Tom Stellard
parent be1489a181
commit 39c406a58f
2 changed files with 42 additions and 2 deletions
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10
lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
View File

@ -1301,6 +1301,7 @@ static AArch64CC::CondCode changeICMPPredToAArch64CC(CmpInst::Predicate P) {
static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert,
MachineRegisterInfo &MRI) {
assert(Reg.isValid() && "Expected valid register!");
bool HasZext = false;
while (MachineInstr *MI = getDefIgnoringCopies(Reg, MRI)) {
unsigned Opc = MI->getOpcode();
@ -1314,6 +1315,9 @@ static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert,
// on the truncated x is the same as the bit number on x.
if (Opc == TargetOpcode::G_ANYEXT || Opc == TargetOpcode::G_ZEXT ||
Opc == TargetOpcode::G_TRUNC) {
if (Opc == TargetOpcode::G_ZEXT)
HasZext = true;
Register NextReg = MI->getOperand(1).getReg();
// Did we find something worth folding?
if (!NextReg.isValid() || !MRI.hasOneNonDBGUse(NextReg))
@ -1342,8 +1346,12 @@ static Register getTestBitReg(Register Reg, uint64_t &Bit, bool &Invert,
std::swap(ConstantReg, TestReg);
VRegAndVal = getConstantVRegValWithLookThrough(ConstantReg, MRI);
}
if (VRegAndVal)
if (VRegAndVal) {
if (HasZext)
C = VRegAndVal->Value.getZExtValue();
else
C = VRegAndVal->Value.getSExtValue();
}
break;
}
case TargetOpcode::G_ASHR:

32
test/CodeGen/AArch64/GlobalISel/opt-fold-xor-tbz-tbnz.mir
View File

@ -117,6 +117,38 @@ body: |
RET_ReallyLR
...
---
name: dont_flip_eq_zext
alignment: 4
legalized: true
regBankSelected: true
tracksRegLiveness: true
body: |
; CHECK-LABEL: name: dont_flip_eq_zext
; CHECK: bb.0:
; CHECK: successors: %bb.0(0x40000000), %bb.1(0x40000000)
; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $wzr
; CHECK: [[SUBREG_TO_REG:%[0-9]+]]:gpr64all = SUBREG_TO_REG 0, [[COPY]], %subreg.sub_32
; CHECK: [[COPY1:%[0-9]+]]:gpr64 = COPY [[SUBREG_TO_REG]]
; CHECK: TBNZX [[COPY1]], 63, %bb.1
; CHECK: B %bb.0
; CHECK: bb.1:
; CHECK: RET_ReallyLR
bb.0:
successors: %bb.0(0x40000000), %bb.1(0x40000000)
%1:gpr(s32) = G_CONSTANT i32 0
%3:gpr(s32) = G_CONSTANT i32 -1
%4:gpr(s32) = G_XOR %1, %3
%5:gpr(s64) = G_ZEXT %4(s32)
%15:gpr(s64) = G_CONSTANT i64 0
%13:gpr(s32) = G_ICMP intpred(slt), %5(s64), %15
%7:gpr(s1) = G_TRUNC %13(s32)
G_BRCOND %7(s1), %bb.1
G_BR %bb.0
bb.1:
RET_ReallyLR
...
---
name: dont_flip_ne
alignment: 4
legalized: true