From: Alexandre Oliva <oliva@adacore.com>
Date: Fri, 19 Sep 2025 19:45:19 +0000 (-0300)
Subject: [ira] avoid resetting ira_reg_equiv for function invariants
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=12992edaa96897d4ce26c3d48fa19c142b0aef28;p=thirdparty%2Fgcc.git

[ira] avoid resetting ira_reg_equiv for function invariants

An aarch64 toolchain built with --enable-default-pie fails
gcc.target/aarch64/sme/nonlocal_goto_[123].c because the register
allocator ends up resetting equivalences, so it concludes it needs to
preserve a rematerializable function invariant across a call instead
of rematerializing it.

Restore the find_reg_equiv_invariant_const logic that was in place
before commit 55a2c3226a3e90a6d65f19710bab1ac377054234 rewrote it and
added a (spurious?) requirement for non-function-invariants to retain
an equivalence when other PIC-related conditions didn't apply.  That
requirement seems either reversed or unnecessary.


for  gcc/ChangeLog

	* ira.cc (setup_reg_equiv): Retain function invariant
	equivalences.
---

diff --git a/gcc/ira.cc b/gcc/ira.cc
index 4eebc9c4c50..3e15966558e 100644
--- a/gcc/ira.cc
+++ b/gcc/ira.cc
@@ -4233,12 +4233,14 @@ setup_reg_equiv (void)
 			    && REGNO (SET_SRC (set)) == (unsigned int) i);
 		x = SET_DEST (set);
 	      }
-	    if (! function_invariant_p (x)
+	    /* If PIC is enabled and the equiv is not a LEGITIMATE_PIC_OPERAND,
+	       we can't use it.  */
+	    if (! CONSTANT_P (x)
 		|| ! flag_pic
 		/* A function invariant is often CONSTANT_P but may
 		   include a register.  We promise to only pass
 		   CONSTANT_P objects to LEGITIMATE_PIC_OPERAND_P.  */
-		|| (CONSTANT_P (x) && LEGITIMATE_PIC_OPERAND_P (x)))
+		|| LEGITIMATE_PIC_OPERAND_P (x))
 	      {
 		/* It can happen that a REG_EQUIV note contains a MEM
 		   that is not a legitimate memory operand.  As later