[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #14 from bonzini at gnu dot org 2008-04-02 09:57 --- committed to trunk as 133828 -- bonzini at gnu dot org changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution||FIXED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #12 from bonzini at gnu dot org 2008-03-11 16:49 --- For 4.4, both mul16 and mul32 will be fixed by the pending patch. The pending patch is what cures the regression part of this bug. --- Comment #13 from bonzini at gnu dot org 2008-03-11 16:49 --- Subject: Bug 35281 Author: bonzini Date: Tue Mar 11 16:48:28 2008 New Revision: 133116 URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=133116 Log: 2008-03-11 Paolo Bonzini [EMAIL PROTECTED] PR rtl-optimization/35281 * expr.c (convert_move): Use a new pseudo for the intermediate from_mode-word_mode result. Modified: trunk/gcc/ChangeLog trunk/gcc/expr.c -- bonzini at gnu dot org changed: What|Removed |Added Keywords||patch http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #12 from bonzini at gnu dot org 2008-03-11 16:49 --- For 4.4, both mul16 and mul32 will be fixed by the pending patch. The pending patch is what cures the regression part of this bug. -- bonzini at gnu dot org changed: What|Removed |Added Keywords||patch http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #10 from bonzini at gnu dot org 2008-03-10 14:14 --- I have a patch. -- bonzini at gnu dot org changed: What|Removed |Added AssignedTo|unassigned at gcc dot gnu |bonzini at gnu dot org |dot org | Status|NEW |ASSIGNED Last reconfirmed|2008-03-05 10:14:59 |2008-03-10 14:14:30 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #11 from bonzini at gnu dot org 2008-03-10 15:19 --- The patch at http://gcc.gnu.org/ml/gcc-patches/2008-03/msg00623.html fixes mul16. -- bonzini at gnu dot org changed: What|Removed |Added URL||http://gcc.gnu.org/ml/gcc- ||patches/2008- ||03/msg00624.html http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #5 from rguenth at gcc dot gnu dot org 2008-03-05 10:27 --- With -O we even have movl$0, %edx movla, %ecx imull %edx, %ecx I wonder why we do not constant-propagate / simplify here? Note that with 4.2 and 4.1 mul16 is also bad. Setting milestone to 4.3.1, only mul32 is a regression. Steven, shouldn't rtl const-prop catch this? -- rguenth at gcc dot gnu dot org changed: What|Removed |Added CC||stevenb dot gcc at gmail dot ||com GCC build triplet|i386-apple-darwin9.2.0 | GCC host triplet|i386-apple-darwin9.2.0 | GCC target triplet|i386-apple-darwin9.2.0 |i?86-*-* Keywords||missed-optimization Priority|P3 |P2 Summary|[4.3 regression] multiply |[4.3/4.4 Regression] |with 0 generated for 64*32- |multiply with 0 generated |64 |for 64*32-64 Target Milestone|4.3.0 |4.3.1 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #6 from ubizjak at gmail dot com 2008-03-05 10:32 ---
4.2 figures out in cse1 pass that:
(insn 9 8 10 2 (parallel [
(set (reg:DI 60 [ b ])
(zero_extend:DI (mem/c/i:SI (symbol_ref:SI (b) var_decl
0xb7caf108 b) [3 b+0 S4 A32])))
(clobber (reg:CC 17 flags))
]) 79 {zero_extendsidi2_32} (nil)
(nil))
...
(insn 11 10 12 2 (parallel [
(set (reg:SI 61)
(mult:SI (reg:SI 62 [ a ])
(subreg:SI (reg:DI 60 [ b ]) 4)))
(clobber (reg:CC 17 flags))
]) 182 {*mulsi3_1} (nil)
(nil))
can simply be substituted with:
(insn 11 9 12 2 (set (reg:SI 61)
(const_int 0 [0x0])) 34 {*movsi_1} (nil)
(nil))
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #7 from ubizjak at gmail dot com 2008-03-05 11:10 ---
It looks that:
2006-11-03 Paolo Bonzini [EMAIL PROTECTED]
Steven Bosscher [EMAIL PROTECTED]
* fwprop.c: New file.
...
* cse.c (fold_rtx_subreg, fold_rtx_mem, fold_rtx_mem_1, find_best_addr,
canon_for_address, table_size): Remove.
(new_basic_block, insert, remove_from_table): Remove references to
table_size.
(fold_rtx): Process SUBREGs and MEMs with equiv_constant, make
simplification loop more straightforward by not calling fold_rtx
recursively.
(equiv_constant): Move here a small part of fold_rtx_subreg,
do not call fold_rtx. Call avoid_constant_pool_reference
to process MEMs.
removed this functionality. Specifically this part:
-/* If this is a constant pool reference, we can fold it into its
- constant to allow better value tracking. */
-if (base GET_CODE (base) == SYMBOL_REF
-CONSTANT_POOL_ADDRESS_P (base))
- {
- rtx constant = get_pool_constant (base);
- enum machine_mode const_mode = get_pool_mode (base);
- rtx new;
-
- if (CONSTANT_P (constant) GET_CODE (constant) != CONST_INT)
- {
- constant_pool_entries_cost = COST (constant);
- constant_pool_entries_regcost = approx_reg_cost (constant);
- }
-
- /* If we are loading the full constant, we have an
- equivalence. */
- if (offset == 0 mode == const_mode)
- return constant;
-
- /* If this actually isn't a constant (weird!), we can't do
- anything. Otherwise, handle the two most common cases:
- extracting a word from a multi-word constant, and
- extracting the low-order bits. Other cases don't seem
- common enough to worry about. */
- if (! CONSTANT_P (constant))
- return x;
-
- if (GET_MODE_CLASS (mode) == MODE_INT
-GET_MODE_SIZE (mode) == UNITS_PER_WORD
-offset % UNITS_PER_WORD == 0
-(new = operand_subword (constant,
- offset / UNITS_PER_WORD,
- 0, const_mode)) != 0)
- return new;
-
- if (((BYTES_BIG_ENDIAN
- offset == GET_MODE_SIZE (GET_MODE (constant)) - 1)
-|| (! BYTES_BIG_ENDIAN offset == 0))
-(new = gen_lowpart (mode, constant)) != 0)
- return new;
- }
This also explains why 4.2 doesn't fold HImode references (Other cases don't
seem common enough to worry about.).
Can we have this functionality back, perhaps also for Other cases, since
there are people that worry about them?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #8 from bonzini at gnu dot org 2008-03-05 13:21 --- Should be handled by this code in simplify_subreg: /* A SUBREG resulting from a zero extension may fold to zero if it extracts higher bits that the ZERO_EXTEND's source bits. */ if (GET_CODE (op) == ZERO_EXTEND bitpos = GET_MODE_BITSIZE (GET_MODE (XEXP (op, 0 return CONST0_RTX (outermode); fwprop does not because the memory is written to. Can anyone run spec moving fwprop *before* CSE instead of after? -- bonzini at gnu dot org changed: What|Removed |Added BugsThisDependsOn||13724 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
[Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32-64
--- Comment #9 from bonzini at gnu dot org 2008-03-05 13:22 --- fwprop does not because the memory is written to (and fwprop does not do alias analysis). -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281
