[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #13 from Martin Liška --- (In reply to ncm from comment #12) > As it is, your probability of failure in 9 and 10 is exactly 1.0. I don't get this? We speak a possibility that we break a stable release branch by a backport that can somehow interact with other parts of the compiler. The purpose of stable branches is to keep them as stable as possible. This bug is a minor performance issue, not any wrong code or a compiler crash.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #12 from ncm at cantrip dot org --- As it is, your probability of failure in 9 and 10 is exactly 1.0.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #11 from Jakub Jelinek --- We usually don't backport optimization improvements, even if they fix regressions, to release branches. There are quite high risks involved.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #10 from ncm at cantrip dot org --- Don't understand, the compiler we are using (9) has the regression. It looks like a trivial backport.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 Martin Liška changed: What|Removed |Added Resolution|--- |FIXED Status|ASSIGNED|RESOLVED --- Comment #9 from Martin Liška --- Fixed on the master, not planning to backport.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #8 from Martin Liška --- (In reply to ncm from comment #6) > The referenced patch seems to have also deleted a fair bit of explanatory > comment text, including a list of possible refinements for selected targets. Sorry for that, I made an overhaul of the pass and I may miss porting of some comments.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #7 from CVS Commits --- The master branch has been updated by Martin Liska : https://gcc.gnu.org/g:5e303cdee1ff01e4b302ef2f913c0bdd84ab967e commit r11-5049-g5e303cdee1ff01e4b302ef2f913c0bdd84ab967e Author: Martin Liska Date: Mon Nov 9 14:26:04 2020 +0100 Prefer bit-test over the jump table. gcc/ChangeLog: PR tree-optimization/97736 * tree-switch-conversion.c (switch_decision_tree::analyze_switch_statement): Prefer bit tests. gcc/testsuite/ChangeLog: PR tree-optimization/97736 * gcc.dg/tree-ssa/switch-1.c: Prefer bit tests. * g++.dg/tree-ssa/pr97736.C: New test.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #6 from ncm at cantrip dot org --- The referenced patch seems to have also deleted a fair bit of explanatory comment text, including a list of possible refinements for selected targets.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 Martin Liška changed: What|Removed |Added Status|RESOLVED|ASSIGNED Resolution|WONTFIX |--- --- Comment #5 from Martin Liška --- All right, let's prefer a bit-test over the jump table.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 --- Comment #4 from Jakub Jelinek --- I disagree with that resolution, expanding it as a bit test is certainly better and shorter too. And it seems even switchconv pass says that it is preferrable to expand it as bit-test, but during expansion it used to be expanded as bit test, but now it just is not.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 Martin Liška changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |WONTFIX --- Comment #3 from Martin Liška --- All right. So for the mentioned test-case we can expand both as jump table and as a bit-test. Since the revision, we prefer the jump table. You can disable that with -fno-jump-tables for the interesting function.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 Martin Liška changed: What|Removed |Added Status|UNCONFIRMED |ASSIGNED Assignee|unassigned at gcc dot gnu.org |marxin at gcc dot gnu.org Last reconfirmed||2020-11-06 Ever confirmed|0 |1 --- Comment #2 from Martin Liška --- Mine then.
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #1 from Jakub Jelinek --- Started with r9-1342-g789410e4824b60f423f7855d68f234e02f9300fb
[Bug tree-optimization/97736] [9/10/11 Regression] switch codegen
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97736 Richard Biener changed: What|Removed |Added Target Milestone|--- |9.4 Component|target |tree-optimization Summary|[9/10 Regression] switch|[9/10/11 Regression] switch |codegen |codegen CC||marxin at gcc dot gnu.org Keywords||missed-optimization
