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[RISCV] Use implicit def/use of SP for PROBED_STACKALLOC*. #139153

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Merged
merged 3 commits into from
May 16, 2025
Merged

[RISCV] Use implicit def/use of SP for PROBED_STACKALLOC*. #139153

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bfa811c
[RISCV] Use implicit def/use of SP for PROBED_STACKALLOC*.
topperc May 8, 2025
82fd7c7
fixup! clang-format
topperc May 8, 2025
33e2c02
Merge remote-tracking branch 'origin/main' into pr/implicit
topperc May 16, 2025
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7 changes: 2 additions & 5 deletions llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -633,7 +633,6 @@ void RISCVFrameLowering::allocateAndProbeStackForRVV(

// It will be expanded to a probe loop in `inlineStackProbe`.
BuildMI(MBB, MBBI, DL, TII->get(RISCV::PROBED_STACKALLOC_RVV))
.addReg(SPReg)
.addReg(TargetReg);

if (EmitCFI) {
Expand Down Expand Up @@ -828,9 +827,7 @@ void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
}

// It will be expanded to a probe loop in `inlineStackProbe`.
BuildMI(MBB, MBBI, DL, TII->get(RISCV::PROBED_STACKALLOC))
.addReg(SPReg)
.addReg(TargetReg);
BuildMI(MBB, MBBI, DL, TII->get(RISCV::PROBED_STACKALLOC)).addReg(TargetReg);

if (EmitCFI) {
// Set the CFA register back to SP.
Expand Down Expand Up @@ -2433,7 +2430,7 @@ void RISCVFrameLowering::inlineStackProbe(MachineFunction &MF,
MI->getOpcode() == RISCV::PROBED_STACKALLOC_RVV) {
MachineBasicBlock::iterator MBBI = MI->getIterator();
DebugLoc DL = MBB.findDebugLoc(MBBI);
Register TargetReg = MI->getOperand(1).getReg();
Register TargetReg = MI->getOperand(0).getReg();
emitStackProbeInline(MBBI, DL, TargetReg,
(MI->getOpcode() == RISCV::PROBED_STACKALLOC_RVV));
MBBI->eraseFromParent();
Expand Down
13 changes: 7 additions & 6 deletions llvm/lib/Target/RISCV/RISCVInstrInfo.td
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Original file line number Diff line number Diff line change
Expand Up @@ -1518,17 +1518,18 @@ def GIAddrRegImm :

/// Stack probing

let hasSideEffects = 1, mayLoad = 1, mayStore = 1, isCodeGenOnly = 1 in {
let hasSideEffects = 1, mayLoad = 1, mayStore = 1, isCodeGenOnly = 1,
Defs = [X2], Uses = [X2] in {
// Probed stack allocation of a constant size, used in function prologues when
// stack-clash protection is enabled.
def PROBED_STACKALLOC : Pseudo<(outs GPR:$sp),
(ins GPR:$target),
[]>,
Sched<[]>;
def PROBED_STACKALLOC_RVV : Pseudo<(outs GPR:$sp),
def PROBED_STACKALLOC : Pseudo<(outs),
(ins GPR:$target),
[]>,
Sched<[]>;
def PROBED_STACKALLOC_RVV : Pseudo<(outs),
(ins GPR:$target),
Comment on lines +1529 to +1530
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(pedantic nit) Not sure it makes any difference, but from liveness point of view this should probably be:

Suggested change
def PROBED_STACKALLOC_RVV : Pseudo<(outs),
(ins GPR:$target),
let Constraints = "$scratch = $target" in
def PROBED_STACKALLOC_RVV : Pseudo<(outs GPR:$scratch),
(ins GPR:$target),

since RVV expansion modifies the $target register.

[]>,
Sched<[]>;
let usesCustomInserter = 1 in
def PROBED_STACKALLOC_DYN : Pseudo<(outs),
(ins GPR:$target),
Expand Down