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[X86][CodeGen] Support flags copy lowering for CCMP/CTEST #91849

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Merged
merged 1 commit into from
May 18, 2024
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[X86][CodeGen] Support flags copy lowering for CCMP/CTEST #91849

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33 changes: 33 additions & 0 deletions llvm/lib/Target/X86/X86FlagsCopyLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -124,6 +124,10 @@ class X86FlagsCopyLoweringPass : public MachineFunctionPass {
MachineBasicBlock::iterator TestPos,
const DebugLoc &TestLoc, MachineInstr &SetCCI,
MachineOperand &FlagUse, CondRegArray &CondRegs);
void rewriteCCMP(MachineBasicBlock &TestMBB,
MachineBasicBlock::iterator TestPos, const DebugLoc &TestLoc,
MachineInstr &CMovI, MachineOperand &FlagUse,
CondRegArray &CondRegs);
};

} // end anonymous namespace
Expand Down Expand Up @@ -613,6 +617,9 @@ bool X86FlagsCopyLoweringPass::runOnMachineFunction(MachineFunction &MF) {
rewriteFCMov(*TestMBB, TestPos, TestLoc, MI, *FlagUse, CondRegs);
} else if (X86::getCondFromSETCC(MI) != X86::COND_INVALID) {
rewriteSetCC(*TestMBB, TestPos, TestLoc, MI, *FlagUse, CondRegs);
} else if (X86::getCondFromCCMP(MI) != X86::COND_INVALID) {
rewriteCCMP(*TestMBB, TestPos, TestLoc, MI, *FlagUse, CondRegs);
FlagsKilled = true;
} else if (MI.getOpcode() == TargetOpcode::COPY) {
rewriteCopy(MI, *FlagUse, CopyDefI);
} else {
Expand Down Expand Up @@ -970,3 +977,29 @@ void X86FlagsCopyLoweringPass::rewriteSetCC(MachineBasicBlock &TestMBB,

SetCCI.eraseFromParent();
}

void X86FlagsCopyLoweringPass::rewriteCCMP(MachineBasicBlock &TestMBB,
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This look very similar to rewriteCMov, can we merge them together?

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Most of the rewrite* functions can be merged together, including rewriteCMov. I will do it after this PR.

MachineBasicBlock::iterator TestPos,
const DebugLoc &TestLoc,
MachineInstr &CCMPI,
MachineOperand &FlagUse,
CondRegArray &CondRegs) {
// First get the register containing this specific condition.
X86::CondCode Cond = X86::getCondFromCCMP(CCMPI);
unsigned CondReg;
bool Inverted;
std::tie(CondReg, Inverted) =
getCondOrInverseInReg(TestMBB, TestPos, TestLoc, Cond, CondRegs);

MachineBasicBlock &MBB = *CCMPI.getParent();

// Insert a direct test of the saved register.
insertTest(MBB, CCMPI.getIterator(), CCMPI.getDebugLoc(), CondReg);

// Rewrite the CCMP/CTEST to use the !ZF flag from the test, and then kill its
// use of the flags afterward.
CCMPI.getOperand(CCMPI.getDesc().getNumOperands() - 1)
.setImm(Inverted ? X86::COND_E : X86::COND_NE);
FlagUse.setIsKill(true);
LLVM_DEBUG(dbgs() << " fixed ccmp/ctest: "; CCMPI.dump());
}
9 changes: 8 additions & 1 deletion llvm/lib/Target/X86/X86InstrInfo.cpp
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Expand Up @@ -3121,7 +3121,8 @@ bool X86InstrInfo::hasCommutePreference(MachineInstr &MI, bool &Commute) const {
int X86::getCondSrcNoFromDesc(const MCInstrDesc &MCID) {
unsigned Opcode = MCID.getOpcode();
if (!(X86::isJCC(Opcode) || X86::isSETCC(Opcode) || X86::isCMOVCC(Opcode) ||
X86::isCFCMOVCC(Opcode)))
X86::isCFCMOVCC(Opcode) || X86::isCCMPCC(Opcode) ||
X86::isCTESTCC(Opcode)))
return -1;
// Assume that condition code is always the last use operand.
unsigned NumUses = MCID.getNumOperands() - MCID.getNumDefs();
Expand Down Expand Up @@ -3157,6 +3158,12 @@ X86::CondCode X86::getCondFromCFCMov(const MachineInstr &MI) {
: X86::COND_INVALID;
}

X86::CondCode X86::getCondFromCCMP(const MachineInstr &MI) {
return X86::isCCMPCC(MI.getOpcode()) || X86::isCTESTCC(MI.getOpcode())
? X86::getCondFromMI(MI)
: X86::COND_INVALID;
}

/// Return the inverse of the specified condition,
/// e.g. turning COND_E to COND_NE.
X86::CondCode X86::GetOppositeBranchCondition(X86::CondCode CC) {
Expand Down
3 changes: 3 additions & 0 deletions llvm/lib/Target/X86/X86InstrInfo.h
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Expand Up @@ -71,6 +71,9 @@ CondCode getCondFromCMov(const MachineInstr &MI);
// Turn CFCMOV instruction into condition code.
CondCode getCondFromCFCMov(const MachineInstr &MI);

// Turn CCMP instruction into condition code.
CondCode getCondFromCCMP(const MachineInstr &MI);

/// GetOppositeBranchCondition - Return the inverse of the specified cond,
/// e.g. turning COND_E to COND_NE.
CondCode GetOppositeBranchCondition(CondCode CC);
Expand Down
51 changes: 51 additions & 0 deletions llvm/test/CodeGen/X86/apx/ccmp-flags-copy-lowering.mir
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@@ -0,0 +1,51 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
# RUN: llc -mtriple=x86_64 -run-pass x86-flags-copy-lowering -verify-machineinstrs -o - %s | FileCheck %s
# Lower various interesting copy patterns of EFLAGS without using LAHF/SAHF.

...
---
name: test_ccmp
body: |
bb.0:
liveins: $edi

; CHECK-LABEL: name: test_ccmp
; CHECK: liveins: $edi
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: MUL32r $edi, implicit-def $eax, implicit-def dead $edx, implicit-def $eflags, implicit $eax
; CHECK-NEXT: [[SETCCr:%[0-9]+]]:gr8 = SETCCr 1, implicit $eflags
; CHECK-NEXT: [[ADD32rr:%[0-9]+]]:gr32 = ADD32rr $edi, $edi, implicit-def $eflags
; CHECK-NEXT: TEST8rr [[SETCCr]], [[SETCCr]], implicit-def $eflags
; CHECK-NEXT: CCMP32rr [[ADD32rr]], [[ADD32rr]], 0, 5, implicit-def $eflags, implicit killed $eflags
; CHECK-NEXT: RET 0, $al
MUL32r $edi, implicit-def $eax, implicit-def dead $edx, implicit-def $eflags, implicit $eax
%1:gr64 = COPY $eflags
%2:gr32 = ADD32rr $edi, $edi, implicit-def $eflags
$eflags = COPY %1
CCMP32rr %2, %2, 0, 1, implicit-def $eflags, implicit $eflags
RET 0, $al

...
---
name: test_ctest
body: |
bb.0:
liveins: $edi

; CHECK-LABEL: name: test_ctest
; CHECK: liveins: $edi
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: MUL32r $edi, implicit-def $eax, implicit-def dead $edx, implicit-def $eflags, implicit $eax
; CHECK-NEXT: [[SETCCr:%[0-9]+]]:gr8 = SETCCr 1, implicit $eflags
; CHECK-NEXT: [[ADD32rr:%[0-9]+]]:gr32 = ADD32rr $edi, $edi, implicit-def $eflags
; CHECK-NEXT: TEST8rr [[SETCCr]], [[SETCCr]], implicit-def $eflags
; CHECK-NEXT: CTEST32rr [[ADD32rr]], [[ADD32rr]], 0, 5, implicit-def $eflags, implicit killed $eflags
; CHECK-NEXT: RET 0, $al
MUL32r $edi, implicit-def $eax, implicit-def dead $edx, implicit-def $eflags, implicit $eax
%1:gr64 = COPY $eflags
%2:gr32 = ADD32rr $edi, $edi, implicit-def $eflags
$eflags = COPY %1
CTEST32rr %2, %2, 0, 1, implicit-def $eflags, implicit $eflags
RET 0, $al

...
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