combine.c (combine_simplify_rtx): Remove a transformation that relies on an invalid assumption about rtl...

	* combine.c (combine_simplify_rtx): Remove a transformation that
	relies on an invalid assumption about rtl sign-extension semantics.

From-SVN: r97941

4 files changed, 22 insertions, 41 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8cb7b42..bd836f3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,10 @@
 2005-04-10  Richard Sandiford  <rsandifo@redhat.com>
 
+	* combine.c (combine_simplify_rtx): Remove a transformation that
+	relies on an invalid assumption about rtl sign-extension semantics.
+
+2005-04-10  Richard Sandiford  <rsandifo@redhat.com>
+
 	* value-prof.c (tree_divmod_fixed_value_transform): Fix arguments
 	to build_int_cst_wide.
 
diff --git a/gcc/combine.c b/gcc/combine.c
index 313a3d9..89866e0 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -3768,47 +3768,6 @@ combine_simplify_rtx (rtx x, enum machine_mode op0_mode, int in_dest)
       SUBST (XEXP (x, 1), temp);
     }
 
-  /* If this is a PLUS, MINUS, or MULT, and the first operand is the
-     sign extension of a PLUS with a constant, reverse the order of the sign
-     extension and the addition. Note that this not the same as the original
-     code, but overflow is undefined for signed values.  Also note that the
-     PLUS will have been partially moved "inside" the sign-extension, so that
-     the first operand of X will really look like:
-         (ashiftrt (plus (ashift A C4) C5) C4).
-     We convert this to
-         (plus (ashiftrt (ashift A C4) C2) C4)
-     and replace the first operand of X with that expression.  Later parts
-     of this function may simplify the expression further.
-
-     For example, if we start with (mult (sign_extend (plus A C1)) C2),
-     we swap the SIGN_EXTEND and PLUS.  Later code will apply the
-     distributive law to produce (plus (mult (sign_extend X) C1) C3).
-
-     We do this to simplify address expressions.  */
-
-  if ((code == PLUS || code == MINUS || code == MULT)
-      && GET_CODE (XEXP (x, 0)) == ASHIFTRT
-      && GET_CODE (XEXP (XEXP (x, 0), 0)) == PLUS
-      && GET_CODE (XEXP (XEXP (XEXP (x, 0), 0), 0)) == ASHIFT
-      && GET_CODE (XEXP (XEXP (XEXP (XEXP (x, 0), 0), 0), 1)) == CONST_INT
-      && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
-      && XEXP (XEXP (XEXP (XEXP (x, 0), 0), 0), 1) == XEXP (XEXP (x, 0), 1)
-      && GET_CODE (XEXP (XEXP (XEXP (x, 0), 0), 1)) == CONST_INT
-      && (temp = simplify_binary_operation (ASHIFTRT, mode,
-					    XEXP (XEXP (XEXP (x, 0), 0), 1),
-					    XEXP (XEXP (x, 0), 1))) != 0)
-    {
-      rtx new
-	= simplify_shift_const (NULL_RTX, ASHIFT, mode,
-				XEXP (XEXP (XEXP (XEXP (x, 0), 0), 0), 0),
-				INTVAL (XEXP (XEXP (x, 0), 1)));
-
-      new = simplify_shift_const (NULL_RTX, ASHIFTRT, mode, new,
-				  INTVAL (XEXP (XEXP (x, 0), 1)));
-
-      SUBST (XEXP (x, 0), simplify_gen_binary (PLUS, mode, new, temp));
-    }
-
   /* If this is a simple operation applied to an IF_THEN_ELSE, try
      applying it to the arms of the IF_THEN_ELSE.  This often simplifies
      things.  Check for cases where both arms are testing the same
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index fea25c4..59255c0 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2005-04-10  Richard Sandiford  <rsandifo@redhat.com>
+
+	* gcc.c-torture/execute/20050410-1.c: New test.
+
 2005-04-09  Alexandre Oliva  <aoliva@redhat.com>
 
 	* gcc.dg/pr20126.c: New.
diff --git a/gcc/testsuite/gcc.c-torture/execute/20050410-1.c b/gcc/testsuite/gcc.c-torture/execute/20050410-1.c
new file mode 100644
index 0000000..c4cd852
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/20050410-1.c
@@ -0,0 +1,13 @@
+int s = 200;
+int __attribute__((noinline))
+foo (void)
+{
+  return (signed char) (s - 100) - 5;
+}
+int
+main (void)
+{
+  if (foo () != 95)
+    abort ();
+  exit (0);
+}