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[RISCV] Align stack size down to a multiple of 16 before using cm.push/pop. #86073

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Merged
merged 2 commits into from
Mar 27, 2024
Merged

[RISCV] Align stack size down to a multiple of 16 before using cm.push/pop. #86073

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4fc2201
[RISCV] Align stack size down to a multiple of 16 before using cm.pus…
topperc Mar 21, 2024
f28b6f3
fixup! fix typo in comment.
topperc Mar 27, 2024
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12 changes: 8 additions & 4 deletions llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -554,8 +554,10 @@ void RISCVFrameLowering::emitPrologue(MachineFunction &MF,
if (RVFI->isPushable(MF) && FirstFrameSetup != MBB.end() &&
FirstFrameSetup->getOpcode() == RISCV::CM_PUSH) {
// Use available stack adjustment in push instruction to allocate additional
// stack space.
uint64_t Spimm = std::min(StackSize, (uint64_t)48);
// stack space. Align the stack size down to a multiple of 16. This is
// needed for RVE.
// FIXME: Can we increase the stack size to a multiple of 16 insead?
uint64_t Spimm = std::min(alignDown(StackSize, 16), (uint64_t)48);
FirstFrameSetup->getOperand(1).setImm(Spimm);
StackSize -= Spimm;
}
Expand Down Expand Up @@ -776,8 +778,10 @@ void RISCVFrameLowering::emitEpilogue(MachineFunction &MF,
if (RVFI->isPushable(MF) && MBBI != MBB.end() &&
MBBI->getOpcode() == RISCV::CM_POP) {
// Use available stack adjustment in pop instruction to deallocate stack
// space.
uint64_t Spimm = std::min(StackSize, (uint64_t)48);
// space. Align the stack size down to a multiple of 16. This is needed for
// RVE.
// FIXME: Can we increase the stack size to a multiple of 16 insead?
uint64_t Spimm = std::min(alignDown(StackSize, 16), (uint64_t)48);
MBBI->getOperand(1).setImm(Spimm);
StackSize -= Spimm;
}
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6 changes: 4 additions & 2 deletions llvm/test/CodeGen/RISCV/zcmp-additional-stack.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,8 @@
define ptr @func(ptr %s, i32 %_c, ptr %incdec.ptr, i1 %0, i8 %conv14) #0 {
; RV32-LABEL: func:
; RV32: # %bb.0: # %entry
; RV32-NEXT: cm.push {ra, s0-s1}, -24
; RV32-NEXT: cm.push {ra, s0-s1}, -16
; RV32-NEXT: addi sp, sp, -8
; RV32-NEXT: .cfi_def_cfa_offset 24
; RV32-NEXT: .cfi_offset ra, -12
; RV32-NEXT: .cfi_offset s0, -8
Expand Down Expand Up @@ -31,7 +32,8 @@ define ptr @func(ptr %s, i32 %_c, ptr %incdec.ptr, i1 %0, i8 %conv14) #0 {
; RV32-NEXT: lw a0, 4(sp) # 4-byte Folded Reload
; RV32-NEXT: sb a0, 0(s0)
; RV32-NEXT: mv a0, s1
; RV32-NEXT: cm.popret {ra, s0-s1}, 24
; RV32-NEXT: addi sp, sp, 8
; RV32-NEXT: cm.popret {ra, s0-s1}, 16
entry:
br label %while.body

Expand Down