From: Alexandre Oliva <aoliva@redhat.com>
Date: Wed, 4 Feb 2015 14:23:33 +0000 (+0000)
Subject: Avoid allocating memory when trying but failing to simplify XOR of AND.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=a720f0efffdf29c2f486e3d825446be4aa77b375;p=gcc.git

Avoid allocating memory when trying but failing to simplify XOR of AND.

for  gcc/ChangeLog

	PR debug/64817
	* simplify-rtx.c (simplify_binary_operation_1): Rewrite
	simplification of XOR of AND to not allocate new rtx before
	committing to a simplification.

From-SVN: r220404
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d63c59cacbe..685f4b8cfca 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2015-02-04  Alexandre Oliva <aoliva@redhat.com>
+
+	PR debug/64817
+	* simplify-rtx.c (simplify_binary_operation_1): Rewrite
+	simplification of XOR of AND to not allocate new rtx before
+	committing to a simplification.
+
 2015-02-04  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* config/aarch64/aarch64-ldpstp.md: Use std::swap instead of
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 5c9e3bf1667..bea9ec353f6 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -2724,12 +2724,31 @@ simplify_binary_operation_1 (enum rtx_code code, machine_mode mode,
 	  HOST_WIDE_INT bval = INTVAL (b);
 	  HOST_WIDE_INT cval = INTVAL (c);
 
-	  rtx na_c
-	    = simplify_binary_operation (AND, mode,
-					 simplify_gen_unary (NOT, mode, a, mode),
-					 c);
+	  /* Instead of computing ~A&C, we compute its negated value,
+	     ~(A|~C).  If it yields -1, ~A&C is zero, so we can
+	     optimize for sure.  If it does not simplify, we still try
+	     to compute ~A&C below, but since that always allocates
+	     RTL, we don't try that before committing to returning a
+	     simplified expression.  */
+	  rtx n_na_c = simplify_binary_operation (IOR, mode, a,
+						  GEN_INT (~cval));
+
 	  if ((~cval & bval) == 0)
 	    {
+	      rtx na_c = NULL_RTX;
+	      if (n_na_c)
+		na_c = simplify_gen_unary (NOT, mode, n_na_c, mode);
+	      else
+		{
+		  /* If ~A does not simplify, don't bother: we don't
+		     want to simplify 2 operations into 3, and if na_c
+		     were to simplify with na, n_na_c would have
+		     simplified as well.  */
+		  rtx na = simplify_unary_operation (NOT, mode, a, mode);
+		  if (na)
+		    na_c = simplify_gen_binary (AND, mode, na, c);
+		}
+
 	      /* Try to simplify ~A&C | ~B&C.  */
 	      if (na_c != NULL_RTX)
 		return simplify_gen_binary (IOR, mode, na_c,
@@ -2738,7 +2757,7 @@ simplify_binary_operation_1 (enum rtx_code code, machine_mode mode,
 	  else
 	    {
 	      /* If ~A&C is zero, simplify A&(~C&B) | ~B&C.  */
-	      if (na_c == const0_rtx)
+	      if (n_na_c == CONSTM1_RTX (mode))
 		{
 		  rtx a_nc_b = simplify_gen_binary (AND, mode, a,
 						    gen_int_mode (~cval & bval,