Hi!
The huge LTO testcase in the PR ICEs, because in a function
where optimize_function_for_speed_p (cfun) and when targetting
-march=i686 optab_handler (movstrict_optab, E_QImode) is
CODE_FOR_movstrictqi, but when the *movstrictqi instruction is being matched
during vregs pass, the condition:
!TARGET_PARTIAL_REG_STALL || optimize_function_for_size_p (cfun)
FAILs. I haven't been able to construct a small testcase that reproduces
that, but in the PR is another one which reproduces the opposite,
where optab_handler (movstrict_optab, E_QImode) is CODE_FOR_nothing
in function where optimize_function_for_size_p (cfun) is true and thus
we unnecessarily create larger code.
From the debugging, seems nothing guarantees that functions with
different optimize_function_for_{size,speed}_p (cfun) will use different
this_fn_optabs in which init_all_optabs records which patterns are disabled
and which are enabled.
The documentation says:
@cindex named patterns and conditions
For a named pattern, the condition may not depend on the data in the
insn being matched, but only the target-machine-type flags. The compiler
needs to test these conditions during initialization in order to learn
exactly which named instructions are available in a particular run.
and while the condition of movstrict<mode> doesn't depend on the data in the
instruction, optimize_function_for_*_p (cfun) is not target-machine-type
flags only either. Furthermore, seems movstrict<mode> is the only named
pattern (one with optab, as verified by preprocessing insn-opinit.c) which
does something like that. Fortunately, the only user of the corresponding
optab does allow the expander to FAIL and even the pattern itself has a
FAIL; already, so this patch just moves the condition into the body as
a condition to FAIL.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2019-12-05 Jakub Jelinek <ja...@redhat.com>
PR target/92791
* config/i386/i386.md (movstrict<mode>): Move test for
TARGET_PARTIAL_REG_STALL and not optimizing for size from
expander's condition to the body - FAIL; in that case.
--- gcc/config/i386/i386.md.jj 2019-12-03 09:22:17.421777187 +0100
+++ gcc/config/i386/i386.md 2019-12-04 16:35:34.193669660 +0100
@@ -2801,10 +2801,11 @@ (define_peephole2
(define_expand "movstrict<mode>"
[(set (strict_low_part (match_operand:SWI12 0 "register_operand"))
(match_operand:SWI12 1 "general_operand"))]
- "!TARGET_PARTIAL_REG_STALL || optimize_function_for_size_p (cfun)"
+ ""
{
gcc_assert (SUBREG_P (operands[0]));
- if (GET_MODE_CLASS (GET_MODE (SUBREG_REG (operands[0]))) != MODE_INT)
+ if ((TARGET_PARTIAL_REG_STALL && optimize_function_for_speed_p (cfun))
+ || GET_MODE_CLASS (GET_MODE (SUBREG_REG (operands[0]))) != MODE_INT)
FAIL;
})
Jakub
