[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306
Oleg Endo olegendo at gcc dot gnu.org changed:
What|Removed |Added
CC||olegendo at gcc dot gnu.org
--- Comment #10 from Oleg Endo olegendo at gcc dot gnu.org ---
(In reply to thopre01 from comment #6)
Author: thopre01
Date: Wed Jun 11 10:04:33 2014
New Revision: 211444
URL: http://gcc.gnu.org/viewcvs?rev=211444root=gccview=rev
Log:
2014-06-11 Thomas Preud'homme thomas.preudho...@arm.com
gcc/
PR tree-optimization/61306
* tree-ssa-math-opts.c (struct symbolic_number): Store type of
expression instead of its size.
(do_shift_rotate): Adapt to change in struct symbolic_number. Return
false to prevent optimization when the result is unpredictable due to
arithmetic right shift of signed type with highest byte is set.
(verify_symbolic_number_p): Adapt to change in struct symbolic_number.
(init_symbolic_number): Likewise.
(find_bswap_or_nop_1): Likewise. Return NULL to prevent optimization
when the result is unpredictable due to sign extension.
gcc/testsuite/
* gcc.c-torture/execute/pr61306-1.c: New test.
* gcc.c-torture/execute/pr61306-2.c: Likewise.
* gcc.c-torture/execute/pr61306-3.c: Likewise.
Added:
trunk/gcc/testsuite/gcc.c-torture/execute/pr61306-1.c
trunk/gcc/testsuite/gcc.c-torture/execute/pr61306-2.c
trunk/gcc/testsuite/gcc.c-torture/execute/pr61306-3.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-ssa-math-opts.c
It seems that after this commit, one SH bswap32 test started to fail.
Comparing the two test reports:
https://gcc.gnu.org/ml/gcc-testresults/2014-06/msg00961.html
https://gcc.gnu.org/ml/gcc-testresults/2014-06/msg01086.html
shows a new failure for gcc.target/sh/pr53568-1.c.
The function
int
test_func_02 (int a)
{
/* 1x swap.w
2x swap.b */
return (((a 0) 0xFF) 24)
| (((a 8) 0xFF) 16)
| (((a 16) 0xFF) 8)
| (((a 24) 0xFF) 0);
}
now fails to produce a bswap32.
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #11 from thopre01 at gcc dot gnu.org --- Confirmed. This is because the compiler will detect that the result of (a 8) depends on the sign of a and thus prevent the optimization. Before this check incorrect code could be generated. Of course in this case since the high bit or discarded with a bitwise AND it is safe. It is possible to detect this by marking the byte with unknown content with a special marker (say 0xff) instead of cancelling the optimization and modify a few places which checks for marker. This can be done for 4.10 but seems to me to invasive for 4.8 and 4.9 where this patch was backported. If you disagree with this we can discuss with the release manager once the patch made to see if they would agree for a backport. Thanks for your report.
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #8 from thopre01 at gcc dot gnu.org --- Author: thopre01 Date: Mon Jun 30 01:58:45 2014 New Revision: 212133 URL: https://gcc.gnu.org/viewcvs?rev=212133root=gccview=rev Log: 2014-06-30 Thomas Preud'homme thomas.preudho...@arm.com Backport from mainline 2014-06-20 Jakub Jelinek ja...@redhat.com 2014-06-11 Thomas Preud'homme thomas.preudho...@arm.com gcc/ PR tree-optimization/61306 * tree-ssa-math-opts.c (struct symbolic_number): Store type of expression instead of its size. (do_shift_rotate): Adapt to change in struct symbolic_number. Return false to prevent optimization when the result is unpredictable due to arithmetic right shift of signed type with highest byte is set. (verify_symbolic_number_p): Adapt to change in struct symbolic_number. (find_bswap_1): Likewise. Return NULL to prevent optimization when the result is unpredictable due to sign extension. (find_bswap): Adapt to change in struct symbolic_number. gcc/testsuite/ * gcc.c-torture/execute/pr61306-1.c: New test. * gcc.c-torture/execute/pr61306-2.c: Likewise. * gcc.c-torture/execute/pr61306-3.c: Likewise. Added: branches/gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/pr61306-1.c branches/gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/pr61306-2.c branches/gcc-4_9-branch/gcc/testsuite/gcc.c-torture/execute/pr61306-3.c Modified: branches/gcc-4_9-branch/gcc/ChangeLog branches/gcc-4_9-branch/gcc/testsuite/ChangeLog branches/gcc-4_9-branch/gcc/tree-ssa-math-opts.c
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #9 from thopre01 at gcc dot gnu.org --- Author: thopre01 Date: Mon Jun 30 02:11:21 2014 New Revision: 212134 URL: https://gcc.gnu.org/viewcvs?rev=212134root=gccview=rev Log: 2014-06-30 Thomas Preud'homme thomas.preudho...@arm.com Backport from mainline 2014-06-20 Jakub Jelinek ja...@redhat.com 2014-06-11 Thomas Preud'homme thomas.preudho...@arm.com gcc/ PR tree-optimization/61306 * tree-ssa-math-opts.c (struct symbolic_number): Store type of expression instead of its size. (do_shift_rotate): Adapt to change in struct symbolic_number. Return false to prevent optimization when the result is unpredictable due to arithmetic right shift of signed type with highest byte is set. (verify_symbolic_number_p): Adapt to change in struct symbolic_number. (find_bswap_1): Likewise. Return NULL to prevent optimization when the result is unpredictable due to sign extension. (find_bswap): Adapt to change in struct symbolic_number. gcc/testsuite/ * gcc.c-torture/execute/pr61306-1.c: New test. * gcc.c-torture/execute/pr61306-2.c: Likewise. * gcc.c-torture/execute/pr61306-3.c: Likewise. Added: branches/gcc-4_8-branch/gcc/testsuite/gcc.c-torture/execute/pr61306-1.c branches/gcc-4_8-branch/gcc/testsuite/gcc.c-torture/execute/pr61306-2.c branches/gcc-4_8-branch/gcc/testsuite/gcc.c-torture/execute/pr61306-3.c Modified: branches/gcc-4_8-branch/gcc/ChangeLog branches/gcc-4_8-branch/gcc/testsuite/ChangeLog branches/gcc-4_8-branch/gcc/tree-ssa-math-opts.c
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #6 from thopre01 at gcc dot gnu.org --- Author: thopre01 Date: Wed Jun 11 10:04:33 2014 New Revision: 211444 URL: http://gcc.gnu.org/viewcvs?rev=211444root=gccview=rev Log: 2014-06-11 Thomas Preud'homme thomas.preudho...@arm.com gcc/ PR tree-optimization/61306 * tree-ssa-math-opts.c (struct symbolic_number): Store type of expression instead of its size. (do_shift_rotate): Adapt to change in struct symbolic_number. Return false to prevent optimization when the result is unpredictable due to arithmetic right shift of signed type with highest byte is set. (verify_symbolic_number_p): Adapt to change in struct symbolic_number. (init_symbolic_number): Likewise. (find_bswap_or_nop_1): Likewise. Return NULL to prevent optimization when the result is unpredictable due to sign extension. gcc/testsuite/ * gcc.c-torture/execute/pr61306-1.c: New test. * gcc.c-torture/execute/pr61306-2.c: Likewise. * gcc.c-torture/execute/pr61306-3.c: Likewise. Added: trunk/gcc/testsuite/gcc.c-torture/execute/pr61306-1.c trunk/gcc/testsuite/gcc.c-torture/execute/pr61306-2.c trunk/gcc/testsuite/gcc.c-torture/execute/pr61306-3.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-ssa-math-opts.c
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 thopre01 at gcc dot gnu.org changed: What|Removed |Added Known to work|4.9.0 |4.10.0 Known to fail||4.8.3, 4.9.0 --- Comment #7 from thopre01 at gcc dot gnu.org --- Although the number of code impacted is bigger since the recent improvement to bswap pass to support memory source, this bug is actually quite old. I'm thus updating the known to work/fail versions accordingly
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #5 from Thomas Preud'homme thomas.preudhomme at arm dot com --- I have a working patch that also pass bootstrap. I'll do a bit more testing and post it for review.
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #4 from Thomas Preud'homme thomas.preudhomme at arm dot com --- I finally managed to find the root cause for the bootstrap failure with my current fix. I shall be able to improve my fix and should hopefully be ready tomorrow.
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 Richard Biener rguenth at gcc dot gnu.org changed: What|Removed |Added Status|UNCONFIRMED |NEW Known to work||4.9.0 Version|unknown |4.10.0 Keywords||wrong-code Last reconfirmed||2014-05-26 CC||thomas.preudhomme at arm dot com Ever confirmed|0 |1 Summary|wrong code at -Os and above |[4.10 Regression] wrong |on x86_64-linux-gnu |code at -Os and above on ||x86_64-linux-gnu Target Milestone|--- |4.10.0 --- Comment #1 from Richard Biener rguenth at gcc dot gnu.org --- Confirmed. Looks like fallout from the bswap improvements.
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #2 from Richard Biener rguenth at gcc dot gnu.org --- 16 bit load in host endianness found at: b.3_7 = (int) load_dst_10; at least the dumping is confusing as well ;) But the issue seems to be that we are missing that a.0_2 and c.1_3 sign-extend. a.0_2 = a; c.1_3 = (char) a.0_2; c = c.1_3; _5 = (int) a.0_2; _6 = (int) c.1_3; b.3_7 = _6 | _5;
[Bug tree-optimization/61306] [4.10 Regression] wrong code at -Os and above on x86_64-linux-gnu
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61306 --- Comment #3 from Thomas Preud'homme thomas.preudhomme at arm dot com --- Indeed. I also noticed that the original bswap code would happily accept signed ssa value and signed cast which can lead to disaster. I worked out a patch for this issue that check the sign of the lhs of the bitwise or expression and use the (unsigned_)?int.I_type_node accordingly but I now get bootstrap failure. I'll provide a patch asap.
