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[PEI][PowerPC] Fix false alarm of stack size limit (#65559)

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PPC64 allows stack size up to ((2^63)-1) bytes. Currently llc reports
```
warning: stack frame size (4294967568) exceeds limit (4294967295) in function 'main'
```
if the stack allocated is larger than 4G.
This commit is contained in:
bzEq 2023-09-08 15:16:00 +08:00 committed by GitHub
parent 785e5737c6
commit d9efcb54c9
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GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 37 additions and 2 deletions
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4
llvm/include/llvm/CodeGen/TargetFrameLowering.h
View File

@ -102,6 +102,10 @@ public:
///
Align getStackAlign() const { return StackAlignment; }
/// getStackThreshold - Return the maximum stack size
///
virtual uint64_t getStackThreshold() const { return UINT_MAX; }
/// alignSPAdjust - This method aligns the stack adjustment to the correct
/// alignment.
///

2
llvm/lib/CodeGen/PrologEpilogInserter.cpp
View File

@ -293,7 +293,7 @@ bool PEI::runOnMachineFunction(MachineFunction &MF) {
MachineFrameInfo &MFI = MF.getFrameInfo();
uint64_t StackSize = MFI.getStackSize();
unsigned Threshold = UINT_MAX;
uint64_t Threshold = TFI->getStackThreshold();
if (MF.getFunction().hasFnAttribute("warn-stack-size")) {
bool Failed = MF.getFunction()
.getFnAttribute("warn-stack-size")

14
llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
View File

@ -2740,3 +2740,17 @@ bool PPCFrameLowering::enableShrinkWrapping(const MachineFunction &MF) const {
return false;
return !MF.getSubtarget<PPCSubtarget>().is32BitELFABI();
}
uint64_t PPCFrameLowering::getStackThreshold() const {
// On PPC64, we use `stux r1, r1, <scratch_reg>` to extend the stack;
// use `add r1, r1, <scratch_reg>` to release the stack frame.
// Scratch register contains a signed 64-bit number, which is negative
// when extending the stack and is positive when releasing the stack frame.
// To make `stux` and `add` paired, the absolute value of the number contained
// in the scratch register should be the same. Thus the maximum stack size
// is (2^63)-1, i.e., LONG_MAX.
if (Subtarget.isPPC64())
return LONG_MAX;
return TargetFrameLowering::getStackThreshold();
}

2
llvm/lib/Target/PowerPC/PPCFrameLowering.h
View File

@ -173,6 +173,8 @@ public:
/// function prologue/epilogue.
bool canUseAsPrologue(const MachineBasicBlock &MBB) const override;
bool canUseAsEpilogue(const MachineBasicBlock &MBB) const override;
uint64_t getStackThreshold() const override;
};
} // End llvm namespace

17
llvm/test/CodeGen/PowerPC/huge-frame-size.ll
View File

@ -1,9 +1,12 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-linux-gnu < %s \
; RUN: 2>&1 | FileCheck --check-prefix=CHECK-LE %s
; RUN: llc -verify-machineinstrs -mtriple=powerpc64-ibm-aix-xcoff < %s \
; RUN: 2>&1 | FileCheck --check-prefix=CHECK-BE %s
; CHECK-NOT: warning: {{.*}} stack frame size ({{.*}}) exceeds limit (4294967295) in function 'foo'
; CHECK-NOT: warning: {{.*}} stack frame size ({{.*}}) exceeds limit (4294967295) in function 'large_stack'
; CHECK: warning: {{.*}} stack frame size ({{.*}}) exceeds limit (4294967295) in function 'warn_on_large_stack'
declare void @bar(ptr)
define void @foo(i8 %x) {
@ -54,3 +57,15 @@ entry:
store volatile i8 %x, ptr %d
ret void
}
define ptr @large_stack() {
%s = alloca [281474976710656 x i8], align 1
%e = getelementptr i8, ptr %s, i64 0
ret ptr %e
}
define ptr @warn_on_large_stack() "warn-stack-size"="4294967295" {
%s = alloca [281474976710656 x i8], align 1
%e = getelementptr i8, ptr %s, i64 0
ret ptr %e
}