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Re: [PATCH (8/7)] Fix a bug in multiply-and-accumulate
On 18/07/11 15:46, Richard Guenther wrote:
Will signedness be always the same? Usually the canonical check to
use would be !useless_type_conversion_p (type, TREE_TYPE (add_rhs)).
The signedness ought to be unimportant - any extend will be based on the
source type, and the signedness should not affect the addition
operation. That said, it really ought to remain correct or else bad
things could happen in later optimizations ....
Here is the patch I plan to commit, when patch 1 is approved, and my
testing is complete.
Andrew
2011-07-21 Andrew Stubbs <ams@codesourcery.com>
gcc/
* tree-ssa-math-opts.c (convert_plusminus_to_widen): Convert add_rhs
to the correct type.
gcc/testsuite/
* gcc.target/arm/wmul-10.c: New file.
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/wmul-10.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-require-effective-target arm_dsp } */
+
+
+unsigned long long
+foo (unsigned short a, unsigned short *b, unsigned short *c)
+{
+ return (unsigned)a + (unsigned long long)*b * (unsigned long long)*c;
+}
+
+/* { dg-final { scan-assembler "umlal" } } */
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -2375,6 +2375,10 @@ convert_plusminus_to_widen (gimple_stmt_iterator *gsi, gimple stmt,
mult_rhs2 = build_and_insert_cast (gsi, loc, tmp, mult_rhs2);
}
+ if (!useless_type_conversion_p (type, TREE_TYPE (add_rhs)))
+ add_rhs = build_and_insert_cast (gsi, loc, create_tmp_var (type, NULL),
+ add_rhs);
+
gimple_assign_set_rhs_with_ops_1 (gsi, wmult_code, mult_rhs1, mult_rhs2,
add_rhs);
update_stmt (gsi_stmt (*gsi));