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From: hartwood@crosslink.net To: gcc-gnats@gcc.gnu.org Subject: other/8553: AltiVec vec_abs broken at -O0 with register keyword Date: Tue, 19 Nov 2002 18:06:00 -0000 [thread overview] Message-ID: <20021112192559.26216.qmail@sources.redhat.com> (raw) >Number: 8553 >Category: other >Synopsis: AltiVec vec_abs broken at -O0 with register keyword >Confidential: no >Severity: serious >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Tue Nov 12 11:36:05 PST 2002 >Closed-Date: >Last-Modified: >Originator: Rick Cellucci >Release: gcc version 3.3 20021104 (experimental) >Organization: >Environment: Configured with: ../gcc3.3/configure --prefix=/usr/local/darwin --enable-altivec --enable-languages=c --with-cpu=7400 --target=powerpc-apple-darwin6.1 >Description: With no optimization, specifying a register vector variable will stomp on the temporary registers used by the vec_abs function, which actually generates 3 vector instructions. >How-To-Repeat: void VecAbsIsBroken (short *image) /* gcc3.3 broken at -O0, works at -O1 and above, remove register keyword to fix */ { short *p; register vector signed short v; p = image; v = vec_ld (0, p); v = vec_abs (v); printf ("%p %hd: ", p, *p); PrintShortVector (v); printf ("\n"); } /* _VecAbsIsBroken: L_VecAbsIsBroken$stub: mfspr r12,256 stw r12,-12(r1) oris r12,r12,0xdfff ori r12,r12,61440 mtspr 256,r12 mflr r0 stw r30,-8(r1) stw r31,-4(r1) stw r0,8(r1) stwu r1,-96(r1) mr r30,r1 bcl 20,31,L4$pb L4$pb: mflr r31 stw r3,120(r30) lwz r0,120(r30) stw r0,56(r30) li r11,0 lwz r9,56(r30) lvx v0,r11,r9 addi r9,r30,64 stvx v0,0,r9 addi r9,r30,64 lvx v1,0,r9 By loading v1 with the input to vec_abs, we doom it to fail vspltisb v1,0 v1 should NOT be used as a temporary register here vsubuhm v13,v1,v1 This just zeroed out v13, not good! vmaxsh v0,v1,v13 So we end up with 0s! addi r9,r30,64 stvx v0,0,r9 */ >Fix: Workaround: Use higher optimization levels. Still, without optimization the code should be generated correctly. >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2002-11-12 19:36 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2002-11-19 18:06 hartwood [this message] 2002-12-19 12:02 aldyh
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