| Summary: | [4.0/4.1 Regression] struct copying code gen | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Andrew Pinski <pinskia> |
| Component: | tree-optimization | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED DUPLICATE | ||
| Severity: | normal | CC: | gcc-bugs, pawel_sikora, rth |
| Priority: | P2 | Keywords: | missed-optimization |
| Version: | 4.1.0 | ||
| Target Milestone: | 4.0.2 | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | 2005-06-23 19:49:02 | |
| Bug Depends on: | 14295, 18268 | ||
| Bug Blocks: | 22156 | ||
I have a fix, it does what I recommended. I am no longer working on this, this is a much harder problem than I sugested. This is basically the same as PR 18268. Can you elaborate on why the VIEW_CONVERT_EXPR experiment failed and perhaps attach the patch you tried? Or does using VIEW_CONVERT_EXPR just expose that we don't do structure propagation? (In reply to comment #3) > Can you elaborate on why the VIEW_CONVERT_EXPR experiment failed and perhaps > attach the patch you tried? Or does using VIEW_CONVERT_EXPR just expose that > we don't do structure propagation? VCE failed because it causes some missed optimizations and really just exposed the fact we don't have structure copy prop. |
Take the following code: struct s { short t; short y1; }; void f(struct s *x, struct s *y) { struct s t = *x; *y = t; } In 3.4.0, we produced: _f: lwz r0,0(r3) stw r0,0(r4) blr but in 4.0.0 and above: _f: lhz r2,2(r3) lha r0,0(r3) sth r2,2(r4) sth r0,0(r4) blr I am starting to think we should use VIEW_CONVERT_EXPR in SRA and store it into a type which is the same as the mode if the mode is not BKL_MODE (RTL mode by the way) and we don't access the temporary variable's fields. That would fix PR 22156 also. Maybe I can look into doing this.