There aren't too many users of the cmpelim pass, and previously they were all
small embedded targets without an FPU.
I'm a bit surprised that Ramana decided to enable this pass for aarch64, as
that target is not so limited as the block comment for the pass describes.
Honestly, whatever is being deleted here ought to have been found earlier,
either via combine or cse. We ought to find out why any changes are made
during this pass for aarch64.
That said, this PR does demonstrate a bug in the handling of fp comparisons in
the presence of -fnon-call-exceptions, so I go ahead and fix that regardless of
what we do with the aarch64 port longer term.
Bootstrap still in progress, but the original testcase is resolved.
r~
* compare-elim.c (struct comparison): Add eh_note.
(find_comparison_dom_walker::before_dom_children): Don't eliminate
a redundant comparison in a different EH region. Purge EH edges if
necessary.
diff --git a/gcc/compare-elim.c b/gcc/compare-elim.c
index 2fbb75b..4ecdd48 100644
--- a/gcc/compare-elim.c
+++ b/gcc/compare-elim.c
@@ -100,6 +100,9 @@ struct comparison
constants. */
rtx in_a, in_b;
+ /* The REG_EH_REGION of the comparison. */
+ rtx eh_note;
+
/* Information about how this comparison is used. */
struct comparison_use uses[MAX_CMP_USE];
@@ -262,6 +265,7 @@ find_comparison_dom_walker::before_dom_children
(basic_block bb)
struct comparison *last_cmp;
rtx insn, next, last_clobber;
bool last_cmp_valid;
+ bool need_purge = false;
bitmap killed;
killed = BITMAP_ALLOC (NULL);
@@ -303,44 +307,60 @@ find_comparison_dom_walker::before_dom_children
(basic_block bb)
if (src)
{
enum machine_mode src_mode = GET_MODE (src);
+ rtx eh_note = NULL;
- /* Eliminate a compare that's redundant with the previous. */
- if (last_cmp_valid
- && rtx_equal_p (last_cmp->in_a, XEXP (src, 0))
- && rtx_equal_p (last_cmp->in_b, XEXP (src, 1)))
- {
- rtx flags, x;
- enum machine_mode new_mode
- = targetm.cc_modes_compatible (last_cmp->orig_mode, src_mode);
+ if (flag_non_call_exceptions)
+ eh_note = find_reg_note (insn, REG_EH_REGION, NULL);
- /* New mode is incompatible with the previous compare mode. */
- if (new_mode == VOIDmode)
- continue;
+ if (!last_cmp_valid)
+ goto dont_delete;
- if (new_mode != last_cmp->orig_mode)
- {
- flags = gen_rtx_REG (src_mode, targetm.flags_regnum);
+ /* Take care that it's in the same EH region. */
+ if (flag_non_call_exceptions
+ && !rtx_equal_p (eh_note, last_cmp->eh_note))
+ goto dont_delete;
- /* Generate new comparison for substitution. */
- x = gen_rtx_COMPARE (new_mode, XEXP (src, 0), XEXP (src, 1));
- x = gen_rtx_SET (VOIDmode, flags, x);
+ /* Make sure the compare is redundant with the previous. */
+ if (!rtx_equal_p (last_cmp->in_a, XEXP (src, 0))
+ || !rtx_equal_p (last_cmp->in_b, XEXP (src, 1)))
+ goto dont_delete;
- if (!validate_change (last_cmp->insn,
- &PATTERN (last_cmp->insn), x, false))
- continue;
+ /* New mode must be compatible with the previous compare mode. */
+ {
+ enum machine_mode new_mode
+ = targetm.cc_modes_compatible (last_cmp->orig_mode, src_mode);
+ if (new_mode == VOIDmode)
+ goto dont_delete;
- last_cmp->orig_mode = new_mode;
- }
+ if (new_mode != last_cmp->orig_mode)
+ {
+ rtx x, flags = gen_rtx_REG (src_mode, targetm.flags_regnum);
- delete_insn (insn);
- continue;
- }
+ /* Generate new comparison for substitution. */
+ x = gen_rtx_COMPARE (new_mode, XEXP (src, 0), XEXP (src, 1));
+ x = gen_rtx_SET (VOIDmode, flags, x);
+ if (!validate_change (last_cmp->insn,
+ &PATTERN (last_cmp->insn), x, false))
+ goto dont_delete;
+
+ last_cmp->orig_mode = new_mode;
+ }
+ }
+
+ /* All tests and substitutions succeeded! */
+ if (eh_note)
+ need_purge = true;
+ delete_insn (insn);
+ continue;
+
+ dont_delete:
last_cmp = XCNEW (struct comparison);
last_cmp->insn = insn;
last_cmp->prev_clobber = last_clobber;
last_cmp->in_a = XEXP (src, 0);
last_cmp->in_b = XEXP (src, 1);
+ last_cmp->eh_note = eh_note;
last_cmp->orig_mode = src_mode;
all_compares.safe_push (last_cmp);
@@ -404,6 +424,11 @@ find_comparison_dom_walker::before_dom_children
(basic_block bb)
}
}
}
+
+ /* If we deleted a compare with a REG_EH_REGION note, we may need to
+ remove EH edges. */
+ if (need_purge)
+ purge_dead_edges (bb);
}
/* Find all comparisons in the function. */
