builtins.c (fold_builtin_logarithm): if N can't be truncated to MODE exactly...

	* builtins.c (fold_builtin_logarithm): if N can't be truncated to
	MODE exactly, then only convert logN(N) -> 1.0 if
	flag_unsafe_math_optimizations is set.

From-SVN: r71322

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d6d762417e8a86aa5242aa99bc018d279ac8015a..df66b3e2640ba51e1aea82f4c88de202212a6027 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2003-09-11  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
+       * builtins.c (fold_builtin_logarithm): if N can't be truncated to
+       MODE exactly, then only convert logN(N) -> 1.0 if
+       flag_unsafe_math_optimizations is set.
+
        * builtins.c (builtin_dconsts_init, dconstpi, dconste,
        init_builtin_dconsts): Delete.
        * emit-rtl.c (dconstpi, dconste): Define.

diff --git a/gcc/builtins.c b/gcc/builtins.c
index 4df0e95b7f6afe3d612a50dd823bb63045d57e75..2e8189d106cddc5c0003be0e78c08fbd17292cc8 100644 (file)
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -5949,16 +5949,21 @@ fold_builtin_logarithm (tree exp, const REAL_VALUE_TYPE *value)
       tree type = TREE_TYPE (TREE_TYPE (fndecl));
       tree arg = TREE_VALUE (arglist);
       const enum built_in_function fcode = builtin_mathfn_code (arg);
-      const REAL_VALUE_TYPE value_mode =
-       real_value_truncate (TYPE_MODE (type), *value);
        
       /* Optimize log*(1.0) = 0.0.  */
       if (real_onep (arg))
        return build_real (type, dconst0);
 
-      /* Optimize logN(N) = 1.0.  */
-      if (real_dconstp (arg, &value_mode))
-       return build_real (type, dconst1);
+      /* Optimize logN(N) = 1.0.  If N can't be truncated to MODE
+         exactly, then only do this if flag_unsafe_math_optimizations.  */
+      if (exact_real_truncate (TYPE_MODE (type), value)
+         || flag_unsafe_math_optimizations)
+        {
+         const REAL_VALUE_TYPE value_truncate =
+           real_value_truncate (TYPE_MODE (type), *value);
+         if (real_dconstp (arg, &value_truncate))
+           return build_real (type, dconst1);
+       }
       
       /* Special case, optimize logN(expN(x)) = x.  */
       if (flag_unsafe_math_optimizations