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* optimization/8832: "asm volatile" code is removed
@ 2002-12-05 14:46 mark
0 siblings, 0 replies; only message in thread
From: mark @ 2002-12-05 14:46 UTC (permalink / raw)
To: gcc-gnats
>Number: 8832
>Category: optimization
>Synopsis: "asm volatile" code is removed
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: wrong-code
>Submitter-Id: net
>Arrival-Date: Thu Dec 05 14:46:02 PST 2002
>Closed-Date:
>Last-Modified:
>Originator: mark
>Release: 3.2 and beyond (2.95.3 was still ok)
>Organization:
>Environment:
>Description:
I have the following test program:
void t(int v)
{
asm volatile ("movaps %xmm0,%xmm1");
if(v&7)
asm volatile ("movaps %xmm1,%xmm2");
asm volatile ("movaps %xmm2,%xmm1");
if(v&7)
asm volatile ("movaps %xmm3,%xmm2");
asm volatile ("movaps %xmm4,%xmm1");
}
With gcc-3.2/3.2.1/3.3 (Invoked with: gcc -O3 -c bug.cpp) produces the following code:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 0f 28 c8 movaps %xmm0,%xmm1
6: f6 45 08 07 testb $0x7,0x8(%ebp)
a: 74 09 je 15 <_Z2tti+0x15>
c: 0f 28 d1 movaps %xmm1,%xmm2
f: 0f 28 ca movaps %xmm2,%xmm1
12: 0f 28 d3 movaps %xmm3,%xmm2
15: 0f 28 cc movaps %xmm4,%xmm1
18: 5d pop %ebp
19: c3 ret
This is not what I want because "movaps %xmm1,%xmm2" is not done if v==7. Is this a bug, or am I doing something wrong ?
The code used to work correctly, gcc 2.95.3 (same system and options) produces the code below, which does excactly what I expect it to do:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 0f 28 c8 movaps %xmm0,%xmm1
6: 8b 45 08 mov 0x8(%ebp),%eax
9: 83 e0 07 and $0x7,%eax
c: 74 03 je 11 <tt__Fi+0x11>
e: 0f 28 d1 movaps %xmm1,%xmm2
11: 0f 28 ca movaps %xmm2,%xmm1
14: 85 c0 test %eax,%eax
16: 74 03 je 1b <tt__Fi+0x1b>
18: 0f 28 d3 movaps %xmm3,%xmm2
1b: 0f 28 cc movaps %xmm4,%xmm1
1e: c9 leave
1f: c3 ret
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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2002-12-05 14:46 optimization/8832: "asm volatile" code is removed mark
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