| Summary: | [4.2 Regression] Over optimization of loop when using -ftree-vectorize | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Anton Blanchard <anton> |
| Component: | tree-optimization | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | dnovillo, dorit, gcc-bugs, victork |
| Priority: | P3 | Keywords: | alias, wrong-code |
| Version: | 4.2.0 | ||
| Target Milestone: | 4.2.0 | ||
| Host: | Target: | ||
| Build: | Known to work: | 4.1.0 | |
| Known to fail: | 4.2.0 4.1.0 | Last reconfirmed: | 2006-02-19 02:26:33 |
| Bug Depends on: | 36244 | ||
| Bug Blocks: | |||
Confirmed, also fails on x86_64. This is a regression from 4.1.0. It also looks like an aliasing issue too as DCE is removing the statements. The problem is that during dce the call to is_hidden_global_store returns false cause the tag is not marked as global/static.
This seems to fix it:
Index: tree-ssa-alias.c
===================================================================
*** tree-ssa-alias.c (revision 110911)
--- tree-ssa-alias.c (working copy)
*************** new_type_alias (tree ptr, tree var)
*** 2638,2643 ****
--- 2638,2651 ----
add_may_alias (tag, al);
}
}
+
+ /* CHECKME:
+ DECL_CONTEXT (tag) = DECL_CONTEXT (var);
+ TREE_PUBLIC (tag) = TREE_PUBLIC (var);
+ TREE_READONLY (tag) = TREE_READONLY (var);
+ */
+ MTAG_GLOBAL (tag) = DECL_EXTERNAL (var);
+ TREE_STATIC (tag) = TREE_STATIC (var);
}
but I don't know if it's the right thing to do in the general case.
Subject: Bug number PR tree-optimization/26359 A patch for this bug has been added to the patch tracker. The mailing list url for the patch is http://gcc.gnu.org/ml/gcc-patches/2006-02/msg01710.html Subject: Bug 26359 Author: dorit Date: Sun Feb 26 09:27:35 2006 New Revision: 111451 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=111451 Log: PR tree-optimization/26359 * tree-ssa-alias.c (new_type_alias): Set fields for new tag. Added: trunk/gcc/testsuite/gcc.dg/vect/dump-tree-dceloop-pr26359.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gcc.dg/vect/vect.exp trunk/gcc/tree-ssa-alias.c Fixed. |
Using a gcc build from today I tried one of the autovectorization test cases and found it over optimized: $ ~/toolchain/install/bin/gcc -v Using built-in specs. Target: powerpc-linux Configured with: /home/anton/toolchain/gcc/gcc/configure --build=powerpc-linux --host=powerpc-linux --target=powerpc-linux --enable-targets=powerpc64-linux --enable-languages=c,c++,fortran --prefix=/home/anton/toolchain/install Thread model: posix gcc version 4.2.0 20060215 (experimental) $ cat example1.c int a[256], b[256], c[256]; foo () { int i; for (i=0; i<256; i++){ a[i] = b[i] + c[i]; } } $ ~/toolchain/install/bin/gcc -c -O1 -ftree-vectorize -ftree-vectorizer-verbose=5 -maltivec -o example1_vect.o example1.c example1.c:5: note: LOOP VECTORIZED. example1.c:5: note: vectorized 1 loops in function. $ objdump -d example1_vect.o example1_vect.o: file format elf32-powerpc Disassembly of section .text: 00000000 <foo>: 0: 94 21 ff f0 stwu r1,-16(r1) 4: 38 00 00 40 li r0,64 8: 7c 09 03 a6 mtctr r0 c: 42 00 00 00 bdnz- c <foo+0xc> 10: 38 21 00 10 addi r1,r1,16 14: 4e 80 00 20 blr