re PR tree-optimization/54295 (Widening multiply-accumulate operation uses wrong value extension)

	PR tree-ssa/54295
	* tree-ssa-math-opts.c (widening_mult_conversion_strippable_p):
	Sign-extension of a zero-extended value can be simplified to
	just zero-extension.

testsuite:
	* gcc.target/arm/pr50318-1.c: Scan for smlal.
	* gcc.target/arm/smlaltb-1.c: XFAIL test.
	* gcc.target/arm/smlaltt-1.c: Likewise.

From-SVN: r191066

gcc/ChangeLog

+2012-09-07  Richard Earnshaw  <rearnsha@arm.com>
+
+	PR tree-ssa/54295
+	* tree-ssa-math-opts.c (widening_mult_conversion_strippable_p):
+	Sign-extension of a zero-extended value can be simplified to
+	just zero-extension.
+
 2012-09-07  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/53667

gcc/testsuite/ChangeLog

+2012-09-07  Richard Earnshaw  <rearnsha@arm.com>
+
+	* gcc.target/arm/pr50318-1.c: Scan for smlal.
+	* gcc.target/arm/smlaltb-1.c: XFAIL test.
+	* gcc.target/arm/smlaltt-1.c: Likewise.
+
 2012-09-07  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gcc.dg/pr44194-1.c: Skip on Alpha and adjust regexp for SPARC64.

gcc/testsuite/gcc.target/arm/pr50318-1.c

@@ -8,4 +8,4 @@ long long test (unsigned int sec, unsigned long long nsecs)
    long)nsecs;
 }
 
-/* { dg-final { scan-assembler "umlal" } } */
+/* { dg-final { scan-assembler "smlal" } } */

gcc/testsuite/gcc.target/arm/smlaltb-1.c

@@ -11,4 +11,4 @@ foo (long long x, int in)
   return x + b * a;
 }
 
-/* { dg-final { scan-assembler "smlaltb\\t" } } */
+/* { dg-final { scan-assembler "smlaltb\\t" { xfail *-*-* } } } */

gcc/testsuite/gcc.target/arm/smlaltt-1.c

@@ -11,4 +11,4 @@ foo (long long x, int in1, int in2)
   return x + b * a;
 }
 
-/* { dg-final { scan-assembler "smlaltt\\t" } } */
+/* { dg-final { scan-assembler "smlaltt\\t" { xfail *-*-* } } } */

gcc/tree-ssa-math-opts.c

@@ -1985,7 +1985,11 @@ widening_mult_conversion_strippable_p (tree result_type, gimple stmt)
 	 the operation and doesn't narrow the range.  */
       inner_op_type = TREE_TYPE (gimple_assign_rhs1 (stmt));
 
-      if (TYPE_UNSIGNED (op_type) == TYPE_UNSIGNED (inner_op_type)
+      /* If the inner-most type is unsigned, then we can strip any
+	 intermediate widening operation.  If it's signed, then the
+	 intermediate widening operation must also be signed.  */
+      if ((TYPE_UNSIGNED (inner_op_type)
+	   || TYPE_UNSIGNED (op_type) == TYPE_UNSIGNED (inner_op_type))
 	  && TYPE_PRECISION (op_type) > TYPE_PRECISION (inner_op_type))
 	return true;