Comment 6 for bug 687406

Created attachment 22691
example case

See the attached example case.

Also reported here:
https://bugs.launchpad.net/gcc-linaro/+bug/687406

When a piece of code containing a multiline macro construct with embedded asm code is first preprocessed then compiled into an object or asm file, the results are different than directly compiling them into an object file or asm code.

The preprocessor step could take place when using -save-temps. It also happens when using ccache or distcc.

Linux kernel arm parts have this kind of code at least in

local_irq_restore() [include/linux/irqflags.h]
  -> raw_local_irq_restore() [arch/arm/include/asm/irqflags.h]

----
Result of example case without -save-temps:

        .file "test.c"
        .text
.globl optimized
        .type optimized, @function
optimized:
.LFB0:
        .cfi_startproc
#APP
# 15 "/tmp/test.c" 1
        nop

# 0 "" 2
#NO_APP
        ret
        .cfi_endproc
.LFE0:
        .size optimized, .-optimized
        .ident "GCC: (GNU) 4.5.1"
        .section .note.GNU-stack,"",@progbits

----

Result of example case with -save-temps:

        .file "test.c"
        .text
.globl optimized
        .type optimized, @function
optimized:
.LFB0:
        .cfi_startproc
        testb $1, flags(%rip)
        je .L2
#APP
# 15 "/tmp/test.c" 1
        nop

# 0 "" 2
#NO_APP
        ret
.L2:
#APP
# 15 "/tmp/test.c" 1
        nop

# 0 "" 2
#NO_APP
        ret
        .cfi_endproc
.LFE0:
        .size optimized, .-optimized
        .ident "GCC: (GNU) 4.5.1"
        .section .note.GNU-stack,"",@progbits