From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 1 Apr 2004 16:27:06 +0000 (+0200)
Subject: re PR c++/14755 (miscompilation in bitfielded signed integers)
X-Git-Tag: releases/gcc-3.3.4~109
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3569be2724944da778338afee2e06f943fb49751;p=thirdparty%2Fgcc.git

re PR c++/14755 (miscompilation in bitfielded signed integers)

	PR c++/14755
	* fold-const.c (fold) <EQ_EXPR>: Properly compute newconst in
	"bitfld++ == const" to "++bitfld == const + incr" transformations.

	* gcc.c-torture/execute/20040331-1.c: New test.

From-SVN: r80301
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6d7b7bbebaf5..08cb57f20adf 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2004-04-01  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/14755
+	* fold-const.c (fold) <EQ_EXPR>: Properly compute newconst in
+	"bitfld++ == const" to "++bitfld == const + incr" transformations.
+
 2004-04-01  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/14069
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 19384e436654..9be3ddfa6abf 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -6049,12 +6049,11 @@ fold (expr)
 	  /* If VAROP is a reference to a bitfield, we must mask
 	     the constant by the width of the field.  */
 	  if (TREE_CODE (TREE_OPERAND (varop, 0)) == COMPONENT_REF
-	      && DECL_BIT_FIELD(TREE_OPERAND (TREE_OPERAND (varop, 0), 1)))
+	      && DECL_BIT_FIELD (TREE_OPERAND (TREE_OPERAND (varop, 0), 1)))
 	    {
 	      tree fielddecl = TREE_OPERAND (TREE_OPERAND (varop, 0), 1);
 	      int size = TREE_INT_CST_LOW (DECL_SIZE (fielddecl));
-	      tree folded_compare;
-	      tree mask = 0;
+	      tree folded_compare, shift;
 
 	      /* First check whether the comparison would come out
 		 always the same.  If we don't do that we would
@@ -6066,25 +6065,12 @@ fold (expr)
 		  || integer_onep (folded_compare))
 		return omit_one_operand (type, folded_compare, varop);
 
-	      if (size < HOST_BITS_PER_WIDE_INT)
-		{
-		  unsigned HOST_WIDE_INT lo = ((unsigned HOST_WIDE_INT) 1
-					       << size) - 1;
-		  mask = build_int_2 (lo, 0);
-		}
-	      else if (size < 2 * HOST_BITS_PER_WIDE_INT)
-		{
-		  HOST_WIDE_INT hi = ((HOST_WIDE_INT) 1
-				      << (size - HOST_BITS_PER_WIDE_INT)) - 1;
-		  mask = build_int_2 (~0, hi);
-		}
-		   
-	      if (mask)
-		{
-		  mask = convert (TREE_TYPE (varop), mask);
-		  newconst = fold (build (BIT_AND_EXPR, TREE_TYPE (varop),
-					  newconst, mask));
-		}
+	      shift = build_int_2 (TYPE_PRECISION (TREE_TYPE (varop)) - size,
+				   0);
+	      newconst = fold (build (LSHIFT_EXPR, TREE_TYPE (varop),
+				      newconst, shift));
+	      newconst = fold (build (RSHIFT_EXPR, TREE_TYPE (varop),
+				      newconst, shift));
 	    }
 
 	  return fold (build (code, type, varop, newconst));
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f3d3cd84eb42..794c523b2fe4 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,4 +1,9 @@
-2004-03-27  Jakub Jelinek  <jakub@redhat.com>
+2004-04-01  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/14755
+	* gcc.c-torture/execute/20040331-1.c: New test.
+
+2004-04-01  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/14069
 	* gcc.dg/20040322-1.c: New test.