[PEI][PowerPC] Fix false alarm of stack size limit #65559
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bzEq
requested review from
arsenm,
nickdesaulniers,
chenzheng1030,
nemanjai and
stefanp-synopsys
| ; CHECK-NOT: warning: {{.*}} stack frame size ({{.*}}) exceeds limit (4294967295) in function 'large_stack' | ||
| define i8* @large_stack() { | ||
| %s = alloca [281474976710656 x i8], align 1 | ||
| %e = getelementptr i8, i8* %s, i64 0 |
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use opaque pointers ptr
Does it really work for a larger-than-4G limit? Do you not hit any other limit in LLVM codegen that might assume uint32_t or a smaller limit? You probably want to try more more stack operations.
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On PPC64, larger-than-4G stack was supported after 5018a5d.
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And we have some internal users using stack larger than 4G.
| @@ -2740,3 +2740,11 @@ bool PPCFrameLowering::enableShrinkWrapping(const MachineFunction &MF) const { | |||
| return false; | |||
| return !MF.getSubtarget<PPCSubtarget>().is32BitELFABI(); | |||
| } | |||
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| uint64_t PPCFrameLowering::getStackThreshold() const { | |||
| // The scratch register of STUX contains a signed negative 64-bit number. | |||
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I'm not very familiar with ppc, but this comment doesn't mean much to me. Maybe other reviewers with more familiarity can triple check it?
…ack frame allocation and deallocation
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Were we always getting this warning on the tests added in 5018a5d?
My initial reaction to this was that the test case needs to show an actual access on a large stack frame, but we already have that in test/CodeGen/PowerPC/huge-frame-size.ll
Maybe it would be nice to add these cases to the same file since this is very related.
Otherwise, LGTM
I think so, I didn't catch that in |
PPC64 allows stack size up to ((2^63)-1) bytes. Currently llc reports
if the stack allocated is larger than 4G.