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* [Bug c/59277] New: x86_64 code generation defects when SSE instructions are disabled
@ 2013-11-24 19:56 aron at udel dot edu
2013-11-24 23:11 ` [Bug target/59277] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: aron at udel dot edu @ 2013-11-24 19:56 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59277
Bug ID: 59277
Summary: x86_64 code generation defects when SSE instructions
are disabled
Product: gcc
Version: 4.7.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: aron at udel dot edu
There are a couple of defects in GCC for x86_64 targets when -mno-sse is
specified.
(1) SSE registers are still generated in various cases. For example, the
following codes will throw an error during compilation because SSE registers
are used:
(1) double test() { return 0.0; }
(2) void test (int n, ...) {
va_list vl; va_start(vl, n);
double foo = va_arg(vl, double);
va_end(vl);
}
(2) va_arg is broken for double types, independently of the bug listed above.
When '-mno-sse' is specified, floating-point numbers are pushed to the stack by
default instead of using the SSE registers; however, the current implementation
for va_arg still looks in the register save area for FP numbers and as such it
returns garbage values.
A fix for the latter should be pretty simple, along the lines of just
defaulting to overflow area for double types similar to the following:
#define va_arg_double(va) \
(*(double*)((va->overflow_arg_area += 8, va->overflow_arg_area
It looked to me like the code to generate the ABI implementation of va_list for
x86 targets is in gcc\config\i386\i386.c.
The only question I have is that I believe fixing these the defects breaks with
the x86_64 ABI specification and wonder whether this would be an issue because
of that.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/59277] x86_64 code generation defects when SSE instructions are disabled
2013-11-24 19:56 [Bug c/59277] New: x86_64 code generation defects when SSE instructions are disabled aron at udel dot edu
@ 2013-11-24 23:11 ` pinskia at gcc dot gnu.org
2013-11-25 9:14 ` rguenth at gcc dot gnu.org
2013-11-25 17:11 ` aron at udel dot edu
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2013-11-24 23:11 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59277
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |X86_64
Component|c |target
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
1) I don't think this is a bug since the abi says to use SSE registers here. If
you want a different abi where SSE is not used you need to create a new abi
2) yes GCC is inconatsaint here but not really a bug due to an abi different.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/59277] x86_64 code generation defects when SSE instructions are disabled
2013-11-24 19:56 [Bug c/59277] New: x86_64 code generation defects when SSE instructions are disabled aron at udel dot edu
2013-11-24 23:11 ` [Bug target/59277] " pinskia at gcc dot gnu.org
@ 2013-11-25 9:14 ` rguenth at gcc dot gnu.org
2013-11-25 17:11 ` aron at udel dot edu
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-11-25 9:14 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59277
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |diagnostic
Target|X86_64 |x86_64-*-*
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-11-25
Ever confirmed|0 |1
Severity|normal |enhancement
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
We still have to follow the ABI. Of course I'd say with -mno-sse you
should get a fatal_error () whenever you run into an ABI piece that requires
SSE registers (instead of silently using them).
We may have one or more (near) duplicates of this bug.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/59277] x86_64 code generation defects when SSE instructions are disabled
2013-11-24 19:56 [Bug c/59277] New: x86_64 code generation defects when SSE instructions are disabled aron at udel dot edu
2013-11-24 23:11 ` [Bug target/59277] " pinskia at gcc dot gnu.org
2013-11-25 9:14 ` rguenth at gcc dot gnu.org
@ 2013-11-25 17:11 ` aron at udel dot edu
2 siblings, 0 replies; 4+ messages in thread
From: aron at udel dot edu @ 2013-11-25 17:11 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59277
--- Comment #4 from Aaron Myles Landwehr <aron at udel dot edu> ---
That is completely fair. Correct me if I'm wrong here, but that also means that
any code that passes doubles as arguments should also get fatal_error() instead
of dropping arguments to the stack as is currently done.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2013-11-25 17:11 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2013-11-24 19:56 [Bug c/59277] New: x86_64 code generation defects when SSE instructions are disabled aron at udel dot edu
2013-11-24 23:11 ` [Bug target/59277] " pinskia at gcc dot gnu.org
2013-11-25 9:14 ` rguenth at gcc dot gnu.org
2013-11-25 17:11 ` aron at udel dot edu
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