https://bugs.llvm.org/show_bug.cgi?id=45275
Bug ID: 45275
Summary: CodeGen doesn't respect stack alignment skew for calls
(hhvm call conv.)
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Common Code Generator Code
Assignee: unassignedb...@nondot.org
Reporter: enge...@in.tum.de
CC: llvm-bugs@lists.llvm.org
When calling a function with the HHVM calling convention, the stack pointer
skewing of 8 bytes is not respected. hhvmcc (on x86-64) has a stack pointer
alignment of 16 bytes, which is skewed by 8 bytes, so that on entry the stack
pointer has a value of 0x...0 (instead of the usual 0x...8 with cdecl). This
skewing is ignored when generating code for a call to a hhvmcc function, making
it impossible to correctly call hhvmcc functions from LLVM.
Example:
declare hhvmcc i64 @callee(i64)
define hhvmcc i64 @caller(i64 %arg) {
%res = notail call hhvmcc i64 @callee(i64 %arg)
ret i64 %res
}
Yields:
caller:
call callee // <-- stack will be mis-aligned
ret
Note that in this example "correct" code is generated when using a tail call.
PS: I'd also be willing to take a look at this myself, but I need some pointers
where to start...
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