re PR tree-optimization/15346 ([tree-ssa] combine two successive divisions)

2014-12-01  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/15346
	* Makefile.in (gimple-match.o-warn): Remove -Wno-unused-parameter,
	add -Wno-unused-but-set-variable.
	* match.pd: Combine two successive divisions.

	* gcc.dg/tree-ssa/forwprop-32.c: New testcase.

From-SVN: r218211

gcc/ChangeLog

 2014-12-01  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/15346
+	* Makefile.in (gimple-match.o-warn): Remove -Wno-unused-parameter,
+	add -Wno-unused-but-set-variable.
+	* match.pd: Combine two successive divisions.
+
+2014-12-01  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/64126
 	* match.pd: Allow conversions in ~A + 1 -> -A, add -A - 1 -> ~A
 	and -1 - A -> ~A.

gcc/Makefile.in

@@ -209,8 +209,8 @@ gengtype-lex.o-warn = -Wno-error
 libgcov-util.o-warn = -Wno-error
 libgcov-driver-tool.o-warn = -Wno-error
 libgcov-merge-tool.o-warn = -Wno-error
-gimple-match.o-warn = -Wno-unused-variable -Wno-unused-parameter
-generic-match.o-warn = -Wno-unused-variable -Wno-unused-parameter
+gimple-match.o-warn = -Wno-unused-variable -Wno-unused-but-set-variable
+generic-match.o-warn = -Wno-unused-variable -Wno-unused-but-set-variable
 
 # All warnings have to be shut off in stage1 if the compiler used then
 # isn't gcc; configure determines that.  WARN_CFLAGS will be either

gcc/match.pd

@@ -129,6 +129,19 @@ along with GCC; see the file COPYING3.  If not see
       && TYPE_UNSIGNED (type))
   (trunc_div @0 @1)))
 
+/* Combine two successive divisions.  */
+(for div (trunc_div ceil_div floor_div round_div exact_div)
+ (simplify
+  (div (div @0 INTEGER_CST@1) INTEGER_CST@2)
+  (with {
+    bool overflow_p;
+    wide_int mul = wi::mul (@1, @2, TYPE_SIGN (type), &overflow_p);
+   }
+   (if (!overflow_p)
+    (div @0 { wide_int_to_tree (type, mul); }))
+   (if (overflow_p)
+    { build_zero_cst (type); }))))
+
 /* Optimize A / A to 1.0 if we don't care about
    NaNs or Infinities.  */
 (simplify

gcc/testsuite/ChangeLog

+2014-12-01  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/15346
+	* gcc.dg/tree-ssa/forwprop-32.c: New testcase.
+
 2014-12-01  Yuri Rumyantsev  <ysrumyan@gmail.com>
 
 	PR tree-optimization/63941

gcc/testsuite/gcc.dg/tree-ssa/forwprop-32.c

+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-forwprop1 -fdump-tree-ccp1" } */
+
+int foo (int x)
+{
+  int tem = x / 3;
+  return tem / 5;
+}
+int bar (int x)
+{
+  int tem = x / 3;
+  return tem / (__INT_MAX__ / 2);
+}
+
+/* { dg-final { scan-tree-dump "x_.\\(D\\) / 15" "forwprop1" } } */
+/* { dg-final { scan-tree-dump "return 0;" "ccp1" } } */
+/* { dg-final { cleanup-tree-dump "forwprop1" } } */
+/* { dg-final { cleanup-tree-dump "ccp1" } } */