From: Vladimir N. Makarov <vmakarov@redhat.com>
Date: Wed, 11 Feb 2026 18:46:34 +0000 (-0500)
Subject: [PR121191, LRA]: Check int modes to generate the right subreg offset when matching... 
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=560766f6e239a8192c42ac5f009f0a4ee2478a61;p=thirdparty%2Fgcc.git

[PR121191, LRA]: Check int modes to generate the right subreg offset when matching reload regs of different modes

In the PR test case (gcc.c-torture/compile/pr35318.c), LRA chose to
match operands in DFmode and SImode modes.  On big endian targets,
this resulted in wrong subreg offset generation and wrong insn
generation.  The offset would be right if the both operands were
scalar integers (see call of reload.cc:operands_match_p in
recog.cc:constrain_operands).  The patch solves the problem.

gcc/ChangeLog:

	PR rtl-optimization/121191
	* lra-constraints.cc (get_matching_reload_reg_subreg): New.
	(get_reload_reg, match_reload): Use it.
---

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 87b18f30c98..8c8c9d69a96 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -682,6 +682,18 @@ canonicalize_reload_addr (rtx addr)
   return addr;
 }
 
+/* Return rtx accessing reload REG matching another reload reg in MODE.  */
+static rtx
+get_matching_reload_reg_subreg (machine_mode mode, rtx reg)
+{
+  if (SCALAR_INT_MODE_P (mode) && SCALAR_INT_MODE_P (GET_MODE (reg)))
+    /* For matching scalar int modes generate the right subreg byte offset for
+       BE targets -- see call of reload.cc:operands_match_p in
+       recog.cc:constrain_operands.  */
+    return lowpart_subreg (mode, reg, GET_MODE (reg));
+  return gen_rtx_SUBREG (mode, reg, 0);
+}
+
 /* Create a new pseudo using MODE, RCLASS, EXCLUDE_START_HARD_REGS, ORIGINAL or
    reuse an existing reload pseudo.  Don't reuse an existing reload pseudo if
    IN_SUBREG_P is true and the reused pseudo should be wrapped up in a SUBREG.
@@ -766,7 +778,7 @@ get_reload_reg (enum op_type type, machine_mode mode, rtx original,
 		if (maybe_lt (GET_MODE_SIZE (GET_MODE (reg)),
 			      GET_MODE_SIZE (mode)))
 		  continue;
-		reg = lowpart_subreg (mode, reg, GET_MODE (reg));
+		reg = get_matching_reload_reg_subreg (mode, reg);
 		if (reg == NULL_RTX || GET_CODE (reg) != SUBREG)
 		  continue;
 	      }
@@ -1134,7 +1146,7 @@ match_reload (signed char out, signed char *ins, signed char *outs,
 	    = lra_create_new_reg_with_unique_value (inmode, in_rtx, goal_class,
 						    exclude_start_hard_regs,
 						    "");
-	  new_out_reg = gen_lowpart_SUBREG (outmode, reg);
+	  new_out_reg = get_matching_reload_reg_subreg (outmode, reg);
 	  LRA_SUBREG_P (new_out_reg) = 1;
 	  /* If the input reg is dying here, we can use the same hard
 	     register for REG and IN_RTX.  We do it only for original
@@ -1153,7 +1165,7 @@ match_reload (signed char out, signed char *ins, signed char *outs,
 						    goal_class,
 						    exclude_start_hard_regs,
 						    "");
-	  new_in_reg = gen_lowpart_SUBREG (inmode, reg);
+	  new_in_reg = get_matching_reload_reg_subreg (inmode, reg);
 	  /* NEW_IN_REG is non-paradoxical subreg.  We don't want
 	     NEW_OUT_REG living above.  We add clobber clause for
 	     this.  This is just a temporary clobber.  We can remove