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Bug#576111: marked as done (gcc-4.4 miscompiles __builtin_expect in -O0)

Your message dated Thu, 01 Apr 2010 02:06:58 +0200
with message-id <4BB3E3A2.40308@debian.org>
and subject line Re: Bug#576111: gcc-4.4 miscompiles __builtin_expect in -O0
has caused the Debian Bug report #576111,
regarding gcc-4.4 miscompiles __builtin_expect in -O0
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
576111: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=576111
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Package: gcc-4.4
Version: 4.4.3-4
Severity: grave

Since gcc-4.4 version 4.4.3-4 (and yes -5 is still affected), gcc miscompiles
__builtin_expect when no optimization is set (at least).

Test case:

    int foo(int t) {
	if (__builtin_expect(t & 0x100, 0))
	    return 0;
	return 1;
    }


Bad assembly:

    gcc -O0 -S -o /dev/stdout a.c
	    .file	"a.c"
	    .text
    .globl foo
	    .type	foo, @function
    foo:
    .LFB0:
	    .cfi_startproc
	    pushq	%rbp
	    .cfi_def_cfa_offset 16
	    movq	%rsp, %rbp
	    .cfi_offset 6, -16
	    .cfi_def_cfa_register 6
	    movl	%edi, -4(%rbp)
	    movl	-4(%rbp), %eax
	    cltq
	    andl	$256, %eax
	    movzbl	%al, %eax            <---------------------
	    testq	%rax, %rax
	    je	.L2
	    movl	$0, %eax
	    jmp	.L3
    .L2:
	    movl	$1, %eax
    .L3:
	    leave
	    ret
	    .cfi_endproc
    .LFE0:
	    .size	foo, .-foo
	    .ident	"GCC: (Debian 4.4.3-5) 4.4.3"
	    .section	.note.GNU-stack,"",@progbits

The buggy line is marked with the arrow.
gcc-4.4 version 4.4.3-3 is correct and doesn't perform the buggy movzbl.

--- End Message ---
--- Begin Message --- 
Version: 4.4.3-6
I realize that this version is not yet in unstable (uploaded, but ftp-master problems). You may want to recheck with the current version in Ubuntu lucid for now.

--- End Message ---
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