[Bug rtl-optimization/47918] [4.6/4.7 Regression] noreturn discovery broke non local gotos on m68k

["mikpe at it dot uu.se" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47918

--- Comment #6 from Mikael Pettersson <mikpe at it dot uu.se> 2011-07-08 09:42:26 UTC ---
I can trigger the bug on i386 too, if I tweak the i386 backend to push function
parameters rather than moving them to pre-allocated stack space, and to
disallow regparm promotion for calls to non-exported functions, via this patch:

--- gcc-4.6-r160123/gcc/config/i386/i386.h.~1~  2010-05-29 16:03:31.000000000
+0200
+++ gcc-4.6-r160123/gcc/config/i386/i386.h      2011-07-08 10:43:46.000000000
+0200
@@ -1513,13 +1513,21 @@ enum reg_class
    prologue and apilogue.  This is not possible without
    ACCUMULATE_OUTGOING_ARGS.  */

+#if 0
 #define ACCUMULATE_OUTGOING_ARGS \
   (TARGET_ACCUMULATE_OUTGOING_ARGS || ix86_cfun_abi () == MS_ABI)
+#else
+#define ACCUMULATE_OUTGOING_ARGS 0
+#endif

 /* If defined, a C expression whose value is nonzero when we want to use PUSH
    instructions to pass outgoing arguments.  */

+#if 0
 #define PUSH_ARGS (TARGET_PUSH_ARGS && !ACCUMULATE_OUTGOING_ARGS)
+#else
+#define PUSH_ARGS 1
+#endif

 /* We want the stack and args grow in opposite directions, even if
    PUSH_ARGS is 0.  */
@@ -1804,7 +1812,11 @@ typedef struct ix86_args {
 #define X86_64_REGPARM_MAX 6
 #define X86_64_MS_REGPARM_MAX 4

+#if 0
 #define X86_32_REGPARM_MAX 3
+#else
+#define X86_32_REGPARM_MAX 0
+#endif

 #define REGPARM_MAX                                                    \
   (TARGET_64BIT ? (TARGET_64BIT_MS_ABI ? X86_64_MS_REGPARM_MAX         \

With that in place gcc still bootstraps ok on i686-linux, but r160124 now
miscompiles non-local-goto-4.c just like on m68k (see the changed and now
incorrect stack offset in the first insn after L4):

--- non-local-goto-4.s-r160123  2011-07-08 10:58:40.000000000 +0200
+++ non-local-goto-4.s-r160124  2011-07-08 11:24:05.000000000 +0200
@@ -25,19 +25,17 @@
        movl    %esp, 8(%esp)
        pushl   36(%esp)
        call    y.1220
-       popl    %eax
+       .p2align 4,,7
+       .p2align 3
+.L2:
 .L4:
-       movl    36(%esp), %eax
+       movl    40(%esp), %eax
        movl    16(%esp), %ebx
        movl    20(%esp), %esi
        movl    24(%esp), %edi
        movl    28(%esp), %ebp
        addl    $32, %esp
        ret
-       .p2align 4,,7
-       .p2align 3
-.L2:
-       jmp     .L4
        .size   x, .-x
        .p2align 4,,15
 .globl main

When I look at dumps everything looks ok up to .188r.asmcons, but in .191r.ira
I see a new load from the stack with the wrong offset.