[Win64] stack probe(alloca, chkstk) is not emitted with variable dynamic stack allocation

[llvmbot]

Bugzilla Link	8777
Resolution	FIXED
Resolved on	Mar 28, 2011 00:24
Version	trunk
OS	Windows XP
Blocks	llvm/llvm-bugzilla-archive#9100
Reporter	LLVM Bugzilla Contributor
CC	@Bigcheese

Extended Description

define i64 @​foo(i64 %n) nounwind {
entry:
%buf = alloca i8, i64 %n, align 1
%r = call i64 @​bar(i8* %buf, i64 %n) nounwind
ret i64 %r
}
declare i64 @​bar(i8* nocapture, i64) nounwind

$ llc -mtriple=x86_64-{win32|mingw32|mingw64}
foo:
pushq %rbp
movq %rsp, %rbp
subq $32, %rsp
movq %rcx, %rdx
leaq 15(%rdx), %rax
andq $-16, %rax
movq %rsp, %rcx
subq %rax, %rcx
movq %rcx, %rsp
callq bar
movq %rbp, %rsp
popq %rbp
ret

It seems alloca might be expanded w/o DYNAMIC_STACKALLOC after X86 DAG->DAG Instruction Selection.

[llvmbot]

See also Michael's patch.
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20101025/110549.html

[llvmbot]

Fixed in r128206, thank you!

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#9100