Patchwork Fix PR c/45969 (excess precision regression)

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Submitter Joseph S. Myers
Date Oct. 14, 2010, 3:51 p.m.
Message ID <Pine.LNX.4.64.1010141550240.2442@digraph.polyomino.org.uk>
Download mbox | patch
Permalink /patch/67835/
State New
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Joseph S. Myers - Oct. 14, 2010, 3:51 p.m.
This patch fixes PR 45969, a regression caused by the C excess
precision changes where build_binary_op tried to compute a semantic
type for a boolean operation on floating-point values when it should
just have let the semantic type be the same type, int, as that used
for computing the result.  I think boolean operations are the only
case where this can occur; I've added an appropriate check to avoid
computing a semantic type in this case.

Bootstrapped with no regressions on i686-pc-linux-gnu.  Applied to
mainline.  Will apply to 4.5 branch subject to testing there.

2010-10-14  Joseph Myers  <joseph@codesourcery.com>

	PR c/45969
	* c-typeck.c (build_binary_op): Don't try to compute a semantic
	type with excess precision for boolean operations.

testsuite:
2010-10-14  Joseph Myers  <joseph@codesourcery.com>

	PR c/45969
	* gcc.c-torture/compile/pr45969-1.c: New test.

Patch

Index: gcc/c-typeck.c
===================================================================
--- gcc/c-typeck.c	(revision 165418)
+++ gcc/c-typeck.c	(working copy)
@@ -9423,6 +9423,10 @@  build_binary_op (location_t location, en
      precision.  */
   bool may_need_excess_precision;
 
+  /* True means this is a boolean operation that converts both its
+     operands to truth-values.  */
+  bool boolean_op = false;
+
   if (location == UNKNOWN_LOCATION)
     location = input_location;
 
@@ -9650,6 +9654,7 @@  build_binary_op (location_t location, en
 	  op0 = c_common_truthvalue_conversion (location, op0);
 	  op1 = c_common_truthvalue_conversion (location, op1);
 	  converted = 1;
+	  boolean_op = true;
 	}
       if (code == TRUTH_ANDIF_EXPR)
 	{
@@ -10192,7 +10197,8 @@  build_binary_op (location_t location, en
   if (build_type == NULL_TREE)
     {
       build_type = result_type;
-      if (type0 != orig_type0 || type1 != orig_type1)
+      if ((type0 != orig_type0 || type1 != orig_type1)
+	  && !boolean_op)
 	{
 	  gcc_assert (may_need_excess_precision && common);
 	  semantic_result_type = c_common_type (orig_type0, orig_type1);
Index: gcc/testsuite/gcc.c-torture/compile/pr45969-1.c
===================================================================
--- gcc/testsuite/gcc.c-torture/compile/pr45969-1.c	(revision 0)
+++ gcc/testsuite/gcc.c-torture/compile/pr45969-1.c	(revision 0)
@@ -0,0 +1,6 @@ 
+/* { dg-options "-std=c89" } */
+void crash() {
+    double l[4];
+    if((l[0]+l[2]) && (l[1]+l[3])){
+    }
+}