https://gcc.gnu.org/g:9dbff9c05520a74e6cd337578f27b56c941f64f3
commit r15-268-g9dbff9c05520a74e6cd337578f27b56c941f64f3
Author: Richard Biener <rguent...@suse.de>
Date: Tue May 7 10:14:19 2024 +0200
Revert "Revert "combine: Don't combine if I2 does not change""
This reverts commit 109f1b28fc94c93096506e3df0c25e331cef19d0.
Diff:
---
gcc/combine.cc | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/gcc/combine.cc b/gcc/combine.cc
index 92b8d98e6c1..71c9abc145c 100644
--- a/gcc/combine.cc
+++ b/gcc/combine.cc
@@ -4196,6 +4196,17 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
rtx_insn *i0,
adjust_for_new_dest (i3);
}
+ /* If I2 didn't change, this is not a combination (but a simplification or
+ canonicalisation with context), which should not be done here. Doing
+ it here explodes the algorithm. Don't. */
+ if (rtx_equal_p (newi2pat, PATTERN (i2)))
+ {
+ if (dump_file)
+ fprintf (dump_file, "i2 didn't change, not doing this\n");
+ undo_all ();
+ return 0;
+ }
+
/* We now know that we can do this combination. Merge the insns and
update the status of registers and LOG_LINKS. */
