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From: "ysrumyan at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/54939] New: Very poor vectorization of loops with complex arithmetic Date: Tue, 16 Oct 2012 14:22:00 -0000 [thread overview] Message-ID: <bug-54939-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54939 Bug #: 54939 Summary: Very poor vectorization of loops with complex arithmetic Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassigned@gcc.gnu.org ReportedBy: ysrumyan@gmail.com Analyzing some performance anomaly for spec2000 I found out that 168.wupwise with vectorization is slower than without it on x86. The main problem is that gcc does not recognize some special idioms of complex addition and multiplication in process of loop vectorization. For example, for a simple zaxpy loop icc genearates 1.6X faster code than gcc. Here is assembly for zaxpy loop produced by icc: ..B1.4: # Preds ..B1.2 ..B1.4 movups (%rsi,%rdx), %xmm2 #7.28 movups 16(%rsi,%rdx), %xmm5 #7.28 movups (%rsi,%rcx), %xmm4 #7.17 movups 16(%rsi,%rcx), %xmm7 #7.17 movddup (%rsi,%rdx), %xmm3 #7.27 incq %r8 #6.10 movddup 16(%rsi,%rdx), %xmm6 #7.27 unpckhpd %xmm2, %xmm2 #7.27 unpckhpd %xmm5, %xmm5 #7.27 mulpd %xmm1, %xmm3 #7.27 mulpd %xmm0, %xmm2 #7.27 mulpd %xmm1, %xmm6 #7.27 mulpd %xmm0, %xmm5 #7.27 addsubpd %xmm2, %xmm3 #7.27 addsubpd %xmm5, %xmm6 #7.27 addpd %xmm3, %xmm4 #7.9 addpd %xmm6, %xmm7 #7.9 movups %xmm4, (%rsi,%rcx) #7.9 movups %xmm7, 16(%rsi,%rcx) #7.9 addq $32, %rsi #6.10 cmpq %rdi, %r8 #6.10 jb ..B1.4 # Prob 64% #6.10 ( I got it with -xSSE4.2 -O3 options). Gor gcc compiler the following options were used: -m64 -mfpmath=sse -march=corei7 -O3 -ffast-math.
next reply other threads:[~2012-10-16 14:22 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-10-16 14:22 ysrumyan at gmail dot com [this message] 2012-10-16 14:37 ` [Bug tree-optimization/54939] " rguenth at gcc dot gnu.org 2012-10-16 14:55 ` ysrumyan at gmail dot com 2012-10-16 15:06 ` ysrumyan at gmail dot com 2012-10-16 15:32 ` rguenth at gcc dot gnu.org 2013-03-27 11:19 ` rguenth at gcc dot gnu.org 2023-07-21 12:28 ` rguenth at gcc dot gnu.org 2023-07-21 12:31 ` rguenth at gcc dot gnu.org
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