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* [Bug c/67167] New: cilkplus vectorization problems @ 2015-08-10 7:56 marcin.krotkiewski at gmail dot com 2015-08-11 8:57 ` [Bug c/67167] " rguenth at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: marcin.krotkiewski at gmail dot com @ 2015-08-10 7:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67167 Bug ID: 67167 Summary: cilkplus vectorization problems Product: gcc Version: 5.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: marcin.krotkiewski at gmail dot com Target Milestone: --- I think there is a problem with vectorization of arithmetic operations in the cilkplus implementation in gcc. I have inspected generated asm of the following two implementations of vector addition (a = a + b). The code is compiled with 'gcc -O3 -mavx -ftree-vectorize -fopt-info-vec -fcilkplus test.c'. // ICC compatibility - alignment hint #ifdef __GNUC__ #define __assume_aligned(lvalueptr, align) lvalueptr = __builtin_assume_aligned (lvalueptr, align) #endif #define RESTRICT __restrict__ typedef double Double; void test(Double * RESTRICT a, Double * RESTRICT b, int size) { int i; __assume_aligned(a, 64); __assume_aligned(b, 64); for(i=0; i<size; i++) a[i] = a[i] + b[i]; } void test_cilkplus1(Double * RESTRICT a, Double * RESTRICT b, int size) { __assume_aligned(a, 64); __assume_aligned(b, 64); a[0:size] = a[0:size] + b[0:size]; } The first code (test) is vectorized as expected - here comes the ASM: .L4: vmovapd (%rdi,%r8), %ymm0 addl $1, %r9d vaddpd (%rsi,%r8), %ymm0, %ymm0 vmovapd %ymm0, (%rdi,%r8) addq $32, %r8 cmpl %r9d, %ecx ja .L4 On the contrary, the second function (test_cilkplus1) is not vectorized: .L21: vmovsd (%rdi,%rax), %xmm0 movl %ecx, %r8d addl $1, %ecx vaddsd (%rsi,%rax), %xmm0, %xmm0 vmovsd %xmm0, (%rdi,%rax) addq $8, %rax cmpl %r8d, %edx jg .L21 Now I have made sure that the compiler understands that there is no aliasing (restrict) and that the vectors are aligned in memory. Clearly this is enough for the standard implementation to produce a vectorized code, but not for the CilkPlus array notation. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/67167] cilkplus vectorization problems 2015-08-10 7:56 [Bug c/67167] New: cilkplus vectorization problems marcin.krotkiewski at gmail dot com @ 2015-08-11 8:57 ` rguenth at gcc dot gnu.org 2015-08-13 7:06 ` rguenth at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2015-08-11 8:57 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67167 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |missed-optimization Status|UNCONFIRMED |NEW Last reconfirmed| |2015-08-11 CC| |kyukhin at gcc dot gnu.org Depends on| |66502 Ever confirmed|0 |1 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- t.c:28:13: note: === get_loop_niters === t.c:28:13: note: not vectorized: number of iterations cannot be computed. t.c:28:13: note: bad loop form. t.c:22:6: note: vectorized 0 loops in function. Which is probably because the loop has two IVs and a combined exit test: <bb 5>: # _32 = PHI <0(4), _21(6)> # _33 = PHI <0(4), _22(6)> ... _21 = _32 + 1; _22 = _33 + 1; _25 = size_9(D) > _22; _23 = size_9(D) > _21; _24 = _23 & _25; if (_24 != 0) goto <bb 6>; else goto <bb 7>; related to PR66502 (proposed patch helps and makes the testcase vectorized, but as noted in the PR regresses another case). Not sure if this can be reasonably addressed in Cilk+ lowering as well? (generate a single IV) Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66502 [Bug 66502] SCCVN can't handle PHIs optimistically optimally ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/67167] cilkplus vectorization problems 2015-08-10 7:56 [Bug c/67167] New: cilkplus vectorization problems marcin.krotkiewski at gmail dot com 2015-08-11 8:57 ` [Bug c/67167] " rguenth at gcc dot gnu.org @ 2015-08-13 7:06 ` rguenth at gcc dot gnu.org 2015-08-13 7:10 ` rguenth at gcc dot gnu.org 2022-01-03 9:50 ` rguenth at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2015-08-13 7:06 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67167 --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- Author: rguenth Date: Thu Aug 13 07:06:10 2015 New Revision: 226850 URL: https://gcc.gnu.org/viewcvs?rev=226850&root=gcc&view=rev Log: 2015-08-13 Richard Biener <rguenther@suse.de> PR tree-optimization/66502 PR tree-optimization/67167 * tree-ssa-sccvn.c (vn_phi_compute_hash): Do not include backedge arguments. (vn_phi_lookup): Adjust. (vn_phi_insert): Likewise. (visit_phi): Prefer to value-number to another PHI node over value-numbering to a PHI argument. (init_scc_vn): Mark DFS back edges. * gcc.dg/tree-ssa/ssa-fre-46.c: New testcase. Added: trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-46.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-ssa-sccvn.c ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/67167] cilkplus vectorization problems 2015-08-10 7:56 [Bug c/67167] New: cilkplus vectorization problems marcin.krotkiewski at gmail dot com 2015-08-11 8:57 ` [Bug c/67167] " rguenth at gcc dot gnu.org 2015-08-13 7:06 ` rguenth at gcc dot gnu.org @ 2015-08-13 7:10 ` rguenth at gcc dot gnu.org 2022-01-03 9:50 ` rguenth at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2015-08-13 7:10 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67167 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- Fixed. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/67167] cilkplus vectorization problems 2015-08-10 7:56 [Bug c/67167] New: cilkplus vectorization problems marcin.krotkiewski at gmail dot com ` (2 preceding siblings ...) 2015-08-13 7:10 ` rguenth at gcc dot gnu.org @ 2022-01-03 9:50 ` rguenth at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2022-01-03 9:50 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67167 Bug 67167 depends on bug 66502, which changed state. Bug 66502 Summary: SCCVN can't handle PHIs optimistically optimally https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66502 What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |RESOLVED Resolution|--- |FIXED ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-01-03 9:50 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-08-10 7:56 [Bug c/67167] New: cilkplus vectorization problems marcin.krotkiewski at gmail dot com 2015-08-11 8:57 ` [Bug c/67167] " rguenth at gcc dot gnu.org 2015-08-13 7:06 ` rguenth at gcc dot gnu.org 2015-08-13 7:10 ` rguenth at gcc dot gnu.org 2022-01-03 9:50 ` rguenth at gcc dot gnu.org
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