From: Philipp Tomsich <philipp.tomsich@vrull.eu>
Date: Fri, 6 Mar 2026 09:54:13 +0000 (+0100)
Subject: ext-dce: Only remove REG_EQUAL/EQUIV notes on successful optimization
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a82d2c6816ff9f3afce67a6cb3cd5d8fe0f9af5d;p=thirdparty%2Fgcc.git

ext-dce: Only remove REG_EQUAL/EQUIV notes on successful optimization

In ext_dce_try_optimize_extension, REG_EQUAL/EQUIV notes were removed
unconditionally after attempting validate_change, even when the
validation failed and the insn was reverted to its original state.
This could cause subsequent passes to generate different (incorrect)
code because they lost the REG_EQUAL hint on an unchanged insn.

Guard the note removal with the 'ok' flag so notes are only stripped
when validate_change actually committed the transformation.

gcc/ChangeLog:

	* ext-dce.cc (ext_dce_try_optimize_extension): Only remove
	REG_EQUAL/EQUIV notes when validate_change succeeds.
---

diff --git a/gcc/ext-dce.cc b/gcc/ext-dce.cc
index 5cc15dd9b44..d0b49241a4b 100644
--- a/gcc/ext-dce.cc
+++ b/gcc/ext-dce.cc
@@ -519,7 +519,8 @@ ext_dce_try_optimize_extension (rtx_insn *insn, rtx set)
       /* INSN may have a REG_EQUAL note indicating that the value was
 	 sign or zero extended.  That note is no longer valid since we've
 	 just removed the extension.  Just wipe the notes.  */
-      remove_reg_equal_equiv_notes (insn, false);
+      if (ok)
+	remove_reg_equal_equiv_notes (insn, false);
     }
   else
     {