[PATCH] Fix simplify_const_unary_operation (PR debug/48204)

[Jakub Jelinek]

Hi!

simplify_const_unary_operation assumes it doesn't have to change anything
in REAL_VALUE_TYPE for FLOAT_EXTEND, which is wrong when FLOAT_EXTENDing
e.g. from SFmode to DDmode or SDmode to DFmode, where the number
needs to be converted from binary to decimal or vice versa.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
ok for trunk/4.6.1?

2011-03-23  Jakub Jelinek  <ja...@redhat.com>

        PR debug/48204
        * simplify-rtx.c (simplify_const_unary_operation): Call
        real_convert when changing mode class with FLOAT_EXTEND.

        * gcc.dg/dfp/pr48204.c: New test.

--- gcc/simplify-rtx.c.jj       2011-03-21 13:00:09.000000000 +0100
+++ gcc/simplify-rtx.c  2011-03-23 16:39:13.000000000 +0100
@@ -1526,7 +1526,8 @@ simplify_const_unary_operation (enum rtx
     }
 
   else if (GET_CODE (op) == CONST_DOUBLE
-          && SCALAR_FLOAT_MODE_P (mode))
+          && SCALAR_FLOAT_MODE_P (mode)
+          && SCALAR_FLOAT_MODE_P (GET_MODE (op)))
     {
       REAL_VALUE_TYPE d, t;
       REAL_VALUE_FROM_CONST_DOUBLE (d, op);
@@ -1549,7 +1550,10 @@ simplify_const_unary_operation (enum rtx
          d = real_value_truncate (mode, d);
          break;
        case FLOAT_EXTEND:
-         /* All this does is change the mode.  */
+         /* All this does is change the mode, unless changing
+            mode class.  */
+         if (GET_MODE_CLASS (mode) != GET_MODE_CLASS (GET_MODE (op)))
+           real_convert (&d, mode, &d);
          break;
        case FIX:
          real_arithmetic (&d, FIX_TRUNC_EXPR, &d, NULL);
--- gcc/testsuite/gcc.dg/dfp/pr48204.c.jj       2011-03-23 16:44:09.000000000 
+0100
+++ gcc/testsuite/gcc.dg/dfp/pr48204.c  2011-03-23 16:43:35.000000000 +0100
@@ -0,0 +1,10 @@
+/* PR debug/48204 */
+/* { dg-do compile } */
+/* { dg-options "-O -fno-tree-ccp -fno-tree-dominator-opts -fno-tree-fre -g" } 
*/
+
+void
+foo (void)
+{
+  float cf = 3.0f;
+  _Decimal64 d64 = cf;
+}

        Jakub