| Summary: | x*x in a loop folded to powf(x,2.) which prevents vectorization | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Francois-Xavier Coudert <fxcoudert> |
| Component: | tree-optimization | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED DUPLICATE | ||
| Severity: | normal | CC: | fxcoudert, gcc-bugs, rguenth |
| Priority: | P3 | Keywords: | missed-optimization |
| Version: | 4.2.0 | ||
| Target Milestone: | --- | ||
| Host: | i686-pc-linux-gnu | Target: | i686-pc-linux-gnu |
| Build: | i686-pc-linux-gnu | Known to work: | |
| Known to fail: | Last reconfirmed: | ||
*** This bug has been marked as a duplicate of 21465 *** Richard, next time you tell someone to file a bug report, please at least look quickly at other bug reports which were filed before telling them to file a new one. Finding the other bug was easy because the summary is correct. I did do a bugzilla search before writing to mailing-list, searching for the error message "relevant stmt not supported" in the comment, but it looks like the error message was changed at some point. |
$ cat a.c void foo (float * restrict x, float * restrict y) { int i; for (i = 0; i < 10000; i++) x[i] = y[i] * y[i]; } $ gcc a.c -O1 -ffast-math -msse -mfpmath=sse -ftree-vectorize -ftree-vectorizer-verbose=5 -std=c99 -c a.c:5: note: Alignment of access forced using peeling. a.c:5: note: Vectorizing an unaligned access. a.c:5: note: not vectorized: relevant stmt not supported: D.1353_14 = __builtin_powf (D.1352_13, 2.0e+0) a.c:5: note: vectorized 0 loops in function. I find in fold-const.c:fold_binary, around line 9091, I found the following: /* Optimize x*x as pow(x,2.0), which is expanded as x*x. */