[Bug target/42313] FAIL: gcc.target/i386/builtin-unreachable.c scan-assembler-not %e[bs]p on i686 darwin

["howarth at nitro dot med dot uc dot edu" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #8 from howarth at nitro dot med dot uc dot edu  2010-09-04 19:13 -------
(In reply to comment #7)
> I fixed the test case to not expect the unimplemented optimization in r157197,
> however, it would be nice to ensure the async signal handlers can handle
> unaligned stacks and to perform this optimization.  I'm fairly certain the
> signal handers have to cope as code gen can do:
> 
> _h:
>         subl    $12, %esp
>         movl    $1, %eax
>         addl    $12, %esp
>         ret
> 
> for int h () { return 1; } and certainly we can take a signal at _h+0, where
> esp isn't aligned.  Given that, we can omit sp alignments for leaf functions
> (and no tail calls either), even on machines where otherwise an alignment is
> required, as long as any variables on the stack are correctly aligned.
> 
> When this optimization is added, we can undo the r157197 change. 
> 

My proposed patch to fix PR36502...

http://gcc.gnu.org/ml/gcc-patches/2010-09/msg00237.html

that enables stack realignment on intel darwin also solves this PR as well.
Comparing the output from gcc trunk before and after my patch, I see...

--- builtin-unreachable.s       2010-09-04 15:12:40.000000000 -0400
+++ builtin-unreachable.trunk_patched   2010-09-04 15:02:45.000000000 -0400
@@ -3,11 +3,7 @@
        .globl _h
 _h:
 LFB0:
-       subl    $12, %esp
-LCFI0:
        movl    $1, %eax
-       addl    $12, %esp
-LCFI1:
        ret
 LFE0:
        .section
__TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support
@@ -39,16 +35,6 @@
        .set L$set$2,LFE0-LFB0
        .long L$set$2
        .byte   0
-       .byte   0x4
-       .set L$set$3,LCFI0-LFB0
-       .long L$set$3
-       .byte   0xe
-       .byte   0x10
-       .byte   0x4
-       .set L$set$4,LCFI1-LCFI0
-       .long L$set$4
-       .byte   0xe
-       .byte   0x4
        .align 2
 LEFDE1:
        .subsections_via_symbols


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42313