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From: Luca "Kronos" Tettamanti <kronoz@tiscali.it> To: gcc-gnats@gcc.gnu.org Subject: optimization/8878: miscompilation with -O and SSE Date: Mon, 09 Dec 2002 09:56:00 -0000 [thread overview] Message-ID: <20021209175316.1DFEF41B4@dreamland.darkstar.lan> (raw) >Number: 8878 >Category: optimization >Synopsis: miscompilation with -O and SSE >Confidential: no >Severity: serious >Priority: low >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Mon Dec 09 09:56:04 PST 2002 >Closed-Date: >Last-Modified: >Originator: >Release: 3.2.1 >Organization: >Environment: System: Linux dreamland 2.4.20-rc3-xfs-acpi #9 Wed Nov 27 18:01:32 CET 2002 i686 unknown Architecture: i686 host: i686-pc-linux-gnu build: i686-pc-linux-gnu target: i686-pc-linux-gnu configured with: ../gcc/configure --prefix=/usr --enable-shared --with-slibdir=/lib --with-gnu-as --with-gnu-ld --enable-threads --enable-languages=c,c++ >Description: gcc produce wrong assembly when using vector instructions through built-in functions and -O. I was benchmarking pure FPU vs. SSE, so the program is a loop that multiply and add 2 vector. >How-To-Repeat: #include <stdio.h> int main(void) { typedef int v4sf __attribute__ ((mode(V4SF))); v4sf a = {2.0, 2.0, 2.0, 2.0}; v4sf b = {1.0, 2.0, 3.0, 4.0}; v4sf c = {0.0, 0.0, 0.0, 0.0}; v4sf d; int i; for(i = 0; i < 1000000; i++) { d = __builtin_ia32_mulps(a, b); c = __builtin_ia32_addps(c, d); } for (i = 0; i < 4; i++) printf("%f ", *(((float *)(&c)) + i)); printf("\n"); return 0; } Compiled with: gcc -Wall -ofloat-sse -march=athlon-xp float-sse.c it gives me the following (correct) output: kronos:~/c$ float-sse 2000000.000000 4000000.000000 6000000.000000 8000000.000000 Compiled with: gcc -O -Wall -ofloat-sse -march=athlon-xp float-sse.c it gives a wrong output: kronos:~/c$ float-sse 8000000.000000 0.000000 0.000000 0.000000 Assembly output available if needed. >Fix: Don't know. >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2002-12-09 17:56 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-12-09 9:56 Luca Kronos Tettamanti [this message] 2002-12-11 6:08 reichelt 2003-04-02 20:16 Janis Johnson 2003-04-02 20:16 Volker Reichelt 2003-04-03 19:36 Janis Johnson 2003-05-02 16:34 reichelt
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