Am 15.08.24 um 10:45 schrieb Richard Sandiford:
When it removes a definition, late-combine tries to update all
uses in notes. It does this using the same insn_propagation class
that it uses for patterns.
However, insn_propagation uses validate_change, which in turn
resets the INSN_CODE. This is inefficient in the best case,
since it forces the pattern to be rerecognised even though
changing a note can't affect the INSN_CODE. But in the PR
it's a correctness problem: resetting INSN_CODE means we lose
the NOOP_INSN_MOVE_CODE, which in turn means that rtl-ssa doesn't
queue it for deletion.
This patch adds a routine specifically for propagating into notes.
A belt-and-braces fix would be to rerecognise noop moves in
function_info::change_insns, but I can't think of a good reason
why that would be necessary, and it could paper over latent bugs.
Tested on aarch64-linux-gnu & x86_64-linux-gnu. OK to install?
Richard
gcc/
PR testsuite/116343
* recog.h (insn_propagation::apply_to_note): Declare.
* recog.cc (insn_propagation::apply_to_note): New function.
* late-combine.cc (insn_combination::substitute_note): Use
apply_to_note instead of apply_to_rvalue.
* rtl-ssa/changes.cc (rtl_ssa::changes_are_worthwhile): Improve
dumping of costs for noop moves.
gcc/testsuite/
PR testsuite/116343
* gcc.dg/torture/pr116343.c: New test.
---
gcc/late-combine.cc | 2 +-
gcc/recog.cc | 13 +++++++++++++
gcc/recog.h | 1 +
gcc/rtl-ssa/changes.cc | 5 ++++-
gcc/testsuite/gcc.dg/torture/pr116343.c | 18 ++++++++++++++++++
5 files changed, 37 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr116343.c
diff --git a/gcc/late-combine.cc b/gcc/late-combine.cc
index 2b62e2956ed..1d81b386c3d 100644
--- a/gcc/late-combine.cc
+++ b/gcc/late-combine.cc
@@ -338,7 +338,7 @@ insn_combination::substitute_note (insn_info *use_insn, rtx
note,
|| REG_NOTE_KIND (note) == REG_EQUIV)
{
insn_propagation prop (use_insn->rtl (), m_dest, m_src);
- return (prop.apply_to_rvalue (&XEXP (note, 0))
+ return (prop.apply_to_note (&XEXP (note, 0))
&& (can_propagate || prop.num_replacements == 0));
}
return true;
diff --git a/gcc/recog.cc b/gcc/recog.cc
index 23e4820180f..615aaabc551 100644
--- a/gcc/recog.cc
+++ b/gcc/recog.cc
@@ -1469,6 +1469,19 @@ insn_propagation::apply_to_rvalue (rtx *loc)
return res;
}
+/* Like apply_to_rvalue, but specifically for the case where *LOC is in
+ a note. This never changes the INSN_CODE. */
+
+bool
+insn_propagation::apply_to_note (rtx *loc)
+{
+ auto old_code = INSN_CODE (insn);
+ bool res = apply_to_rvalue (loc);
+ if (INSN_CODE (insn) != old_code)
+ INSN_CODE (insn) = old_code;
+ return res;
+}
+
/* Check whether INSN matches a specific alternative of an .md pattern. */
bool
diff --git a/gcc/recog.h b/gcc/recog.h
index 87a5803dec0..1dccce78ba4 100644
--- a/gcc/recog.h
+++ b/gcc/recog.h
@@ -121,6 +121,7 @@ public:
insn_propagation (rtx_insn *, rtx, rtx, bool = true);
bool apply_to_pattern (rtx *);
bool apply_to_rvalue (rtx *);
+ bool apply_to_note (rtx *);
/* Return true if we should accept a substitution into the address of
memory expression MEM. Undoing changes OLD_NUM_CHANGES and up restores
diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc
index a30f000191e..0476296607b 100644
--- a/gcc/rtl-ssa/changes.cc
+++ b/gcc/rtl-ssa/changes.cc
@@ -228,7 +228,10 @@ rtl_ssa::changes_are_worthwhile (array_slice<insn_change
*const> changes,
for (const insn_change *change : changes)
if (!change->is_deletion ())
{
- fprintf (dump_file, " %c %d", sep, change->new_cost);
+ if (INSN_CODE (change->rtl ()) == NOOP_MOVE_INSN_CODE)
+ fprintf (dump_file, " %c nop", sep);
+ else
+ fprintf (dump_file, " %c %d", sep, change->new_cost);
sep = '+';
}
if (weighted_new_cost != 0)
diff --git a/gcc/testsuite/gcc.dg/torture/pr116343.c
b/gcc/testsuite/gcc.dg/torture/pr116343.c
new file mode 100644
index 00000000000..ad13f0fc21c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr116343.c
@@ -0,0 +1,18 @@
+// { dg-additional-options "-fschedule-insns -fno-thread-jumps -fno-dce" }
Hi, this fails on machines that don't support scheduling:
cc1: warning: instruction scheduling not supported on this target machine
FAIL: gcc.dg/torture/pr116343.c -O0 (test for excess errors)
Excess errors:
cc1: warning: instruction scheduling not supported on this target machine
Johann
+
+int a, b, c;
+volatile int d;
+int e(int f, int g) { return g > 1 ? 1 : f >> g; }
+int main() {
+ int *i = &a;
+ long j[1];
+ if (a)
+ while (1) {
+ a ^= 1;
+ if (*i)
+ while (1)
+ ;
+ b = c && e((d, 1) >= 1, j[0]);
+ }
+ return 0;
+}
