[LLVMbugs] [Bug 22068] Bad code generation on i686 w/ inline assembly and -mstackrealign

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Dec 30 16:33:36 PST 2014


http://llvm.org/bugs/show_bug.cgi?id=22068

Reid Kleckner <rnk at google.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |rnk at google.com
         Resolution|---                         |DUPLICATE

--- Comment #1 from Reid Kleckner <rnk at google.com> ---
This is a known issue with our stack realignment that happens with rbx on x64.

I ran into and tried to make us fatal error in these situations:
http://reviews.llvm.org/D1317

I'm going to dupe this against PR16830, since it's older and basically the same
problem. The core issue is that aligned stack space with a moving SP requires
three pointers to the stack:
- ebp to reference args in memory
- esp to handle calls and dynamic allocas
- "base pointer" (currently esi/rbx) to reference the aligned space

Keeping ebp where it is also keeps a reference to the return address, which is
good for frame pointer based unwinders.

*** This bug has been marked as a duplicate of bug 16830 ***

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