https://gcc.gnu.org/g:5031df5d1f4954304c618efd2de029edc6b3699f
commit r15-3204-g5031df5d1f4954304c618efd2de029edc6b3699f
Author: Hans-Peter Nilsson <h...@axis.com>
Date: Mon Jul 8 03:55:27 2024 +0200
combine.cc (make_more_copies): Copy attributes from the original pseudo,
PR115883
The first of the late-combine passes, propagates some of the copies
made during the (in-time-)combine pass in make_more_copies into the
users of the "original" pseudo registers and removes the "old"
pseudos. That effectively removes attributes such as REG_POINTER,
which matter to LRA. The quoted PR is for an ICE-manifesting bug that
was exposed by the late-combine pass and went back to hiding with this
patch until commit r15-2937-g3673b7054ec2, the fix for PR116236, when
it was actually fixed. To wit, this patch is only incidentally
related to that bug.
In other words, the REG_POINTER attribute should not be required for
LRA to work correctly. This patch merely corrects state for those
propagated register-uses to ante late-combine.
For reasons not investigated, this fixes a failing test
"FAIL: gcc.dg/guality/pr54200.c -Og -DPREVENT_OPTIMIZATION line 20 z == 3"
for x86_64-linux-gnu.
PR middle-end/115883
* combine.cc (make_more_copies): Copy attributes from the original
pseudo to the new copy.
Diff:
---
gcc/combine.cc | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/gcc/combine.cc b/gcc/combine.cc
index 40e92941e428..fef06a6cdc08 100644
--- a/gcc/combine.cc
+++ b/gcc/combine.cc
@@ -15102,6 +15102,12 @@ make_more_copies (void)
continue;
rtx new_reg = gen_reg_rtx (GET_MODE (dest));
+
+ /* The "original" pseudo copies have important attributes
+ attached, like pointerness. We want that for these copies
+ too, for use by insn recognition and later passes. */
+ set_reg_attrs_from_value (new_reg, dest);
+
rtx_insn *new_insn = gen_move_insn (new_reg, src);
SET_SRC (set) = new_reg;
emit_insn_before (new_insn, insn);
