[patch tree-optimization]: allow branch-cost optimization for truth-and/or on mode-expanded simple boolean-operands

[Kai Tietz <ktietz at redhat dot com>]

Hello,

this patch re-enables the branch-cost optimization on simple boolean-typed operands, which are casted to a wider integral type.  This happens due casts from
boolean-types are preserved, but FE might expands simple-expression to wider mode.

I added two tests for already working branch-cost optimization for IA-architecture and
two for explicit checking for boolean-type.

ChangeLog

2011-10-20  Kai Tietz  <ktietz@redhat.com>

        * fold-const.c (simple_operand_p_2): Handle integral
        casts from boolean-operands.

2011-10-20  Kai Tietz  <ktietz@redhat.com>

        * gcc.target/i386/branch-cost1.c: New test.
        * gcc.target/i386/branch-cost2.c: New test.
        * gcc.target/i386/branch-cost3.c: New test.
        * gcc.target/i386/branch-cost4.c: New test.

Bootstrapped and regression tested on x86_64-unknown-linux-gnu for all languages including Ada and Obj-C++.  Ok for apply?

Regards,
Kai

Index: gcc-head/gcc/testsuite/gcc.target/i386/branch-cost2.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.target/i386/branch-cost2.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-gimple -mbranch-cost=2" } */
+
+extern int doo (void);
+
+int
+foo (int a, int b)
+{
+  if (a && b)
+   return doo ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "if " 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times " & " 1 "gimple" } } */
+/* { dg-final { cleanup-tree-dump "gimple" } } */
Index: gcc-head/gcc/testsuite/gcc.target/i386/branch-cost3.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.target/i386/branch-cost3.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-gimple -mbranch-cost=2" } */
+
+extern int doo (void);
+
+int
+foo (_Bool a, _Bool b)
+{
+  if (a && b)
+   return doo ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "if " 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-times " & " 1 "gimple" } } */
+/* { dg-final { cleanup-tree-dump "gimple" } } */
Index: gcc-head/gcc/testsuite/gcc.target/i386/branch-cost4.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.target/i386/branch-cost4.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-gimple -mbranch-cost=0" } */
+
+extern int doo (void);
+
+int
+foo (_Bool a, _Bool b)
+{
+  if (a && b)
+   return doo ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "if " 2 "gimple" } } */
+/* { dg-final { scan-tree-dump-not " & " "gimple" } } */
+/* { dg-final { cleanup-tree-dump "gimple" } } */
Index: gcc-head/gcc/fold-const.c
===================================================================
--- gcc-head.orig/gcc/fold-const.c
+++ gcc-head/gcc/fold-const.c
@@ -3706,6 +3706,19 @@ simple_operand_p_2 (tree exp)
   /* Strip any conversions that don't change the machine mode.  */
   STRIP_NOPS (exp);
 
+  /* Handle integral widening casts from boolean-typed
+     expressions as simple.  This happens due casts from
+     boolean-types are preserved, but FE might expands
+     simple-expression to wider mode.  */
+  if (INTEGRAL_TYPE_P (TREE_TYPE (exp))
+      && CONVERT_EXPR_P (exp)
+      && TREE_CODE (TREE_TYPE (TREE_OPERAND (exp, 0)))
+	 == BOOLEAN_TYPE)
+    {
+      exp = TREE_OPERAND (exp, 0);
+      STRIP_NOPS (exp);
+    }
+
   code = TREE_CODE (exp);
 
   if (TREE_SIDE_EFFECTS (exp)
Index: gcc-head/gcc/testsuite/gcc.target/i386/branch-cost1.c
===================================================================
--- /dev/null
+++ gcc-head/gcc/testsuite/gcc.target/i386/branch-cost1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-gimple -mbranch-cost=0" } */
+
+extern int doo (void);
+
+int
+foo (int a, int b)
+{
+  if (a && b)
+   return doo ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "if " 2 "gimple" } } */
+/* { dg-final { scan-tree-dump-not " & " "gimple" } } */
+/* { dg-final { cleanup-tree-dump "gimple" } } */