From: Richard Sandiford <richard.sandiford@arm.com>
Date: Fri, 27 Oct 2023 15:37:11 +0000 (+0100)
Subject: recog: Fix propagation into ASM_OPERANDS
X-Git-Tag: basepoints/gcc-15~5159
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2672c60917d12260154de5d7bf668c55f2a0e62e;p=thirdparty%2Fgcc.git

recog: Fix propagation into ASM_OPERANDS

An inline asm with multiple output operands is represented as a
parallel set in which the SET_SRCs are the same (shared) ASM_OPERANDS.
insn_propagation didn't account for this, and instead propagated
into each ASM_OPERANDS individually.  This meant that it could
apply a substitution X->Y to Y itself, which (a) could create
circularity and (b) would be semantically wrong in any case,
since Y might use a different value of X.

This patch checks explicitly for parallels involving ASM_OPERANDS,
just like combine does.

gcc/
	* recog.cc (insn_propagation::apply_to_pattern_1): Handle shared
	ASM_OPERANDS.
---

diff --git a/gcc/recog.cc b/gcc/recog.cc
index e12b4c9500e3..3bd2d73c2590 100644
--- a/gcc/recog.cc
+++ b/gcc/recog.cc
@@ -1339,13 +1339,26 @@ insn_propagation::apply_to_pattern_1 (rtx *loc)
 	      && apply_to_pattern_1 (&COND_EXEC_CODE (body)));
 
     case PARALLEL:
-      {
-	int last = XVECLEN (body, 0) - 1;
-	for (int i = 0; i < last; ++i)
-	  if (!apply_to_pattern_1 (&XVECEXP (body, 0, i)))
-	    return false;
-	return apply_to_pattern_1 (&XVECEXP (body, 0, last));
-      }
+      for (int i = 0; i < XVECLEN (body, 0); ++i)
+	{
+	  rtx *subloc = &XVECEXP (body, 0, i);
+	  if (GET_CODE (*subloc) == SET)
+	    {
+	      if (!apply_to_lvalue_1 (SET_DEST (*subloc)))
+		return false;
+	      /* ASM_OPERANDS are shared between SETs in the same PARALLEL.
+		 Only process them on the first iteration.  */
+	      if ((i == 0 || GET_CODE (SET_SRC (*subloc)) != ASM_OPERANDS)
+		  && !apply_to_rvalue_1 (&SET_SRC (*subloc)))
+		return false;
+	    }
+	  else
+	    {
+	      if (!apply_to_pattern_1 (subloc))
+		return false;
+	    }
+	}
+      return true;
 
     case ASM_OPERANDS:
       for (int i = 0, len = ASM_OPERANDS_INPUT_LENGTH (body); i < len; ++i)