The following adds the ability to transform
if (x != 0)
x = x / 10;
to
x = x / 10;
as requested by PR. Plus it adds some more ops where such transform
is possible.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2016-07-13 Richard Biener <rguent...@suse.de>
PR tree-optimization/24574
* tree-ssa-phiopt.c (absorbing_element_p): Pass in argument
position and add shift, rotate, divison and modulo support
for left zero.
(value_replacement): Pass in argument position to absorbing_element_p.
* gcc.dg/pr24574.c: New testcase.
Index: gcc/tree-ssa-phiopt.c
===================================================================
--- gcc/tree-ssa-phiopt.c (revision 238242)
+++ gcc/tree-ssa-phiopt.c (working copy)
@@ -812,7 +812,7 @@ neutral_element_p (tree_code code, tree
/* Returns true if ARG is an absorbing element for operation CODE. */
static bool
-absorbing_element_p (tree_code code, tree arg)
+absorbing_element_p (tree_code code, tree arg, bool right)
{
switch (code)
{
@@ -823,6 +823,21 @@ absorbing_element_p (tree_code code, tre
case BIT_AND_EXPR:
return integer_zerop (arg);
+ case LSHIFT_EXPR:
+ case RSHIFT_EXPR:
+ case LROTATE_EXPR:
+ case RROTATE_EXPR:
+ case TRUNC_DIV_EXPR:
+ case CEIL_DIV_EXPR:
+ case FLOOR_DIV_EXPR:
+ case ROUND_DIV_EXPR:
+ case EXACT_DIV_EXPR:
+ case TRUNC_MOD_EXPR:
+ case CEIL_MOD_EXPR:
+ case FLOOR_MOD_EXPR:
+ case ROUND_MOD_EXPR:
+ return !right && integer_zerop (arg);
+
default:
return false;
}
@@ -994,9 +1009,10 @@ value_replacement (basic_block cond_bb,
&& operand_equal_for_phi_arg_p (rhs1, cond_lhs)
&& neutral_element_p (code_def, cond_rhs, false))
|| (operand_equal_for_phi_arg_p (arg1, cond_rhs)
- && (operand_equal_for_phi_arg_p (rhs2, cond_lhs)
- || operand_equal_for_phi_arg_p (rhs1, cond_lhs))
- && absorbing_element_p (code_def, cond_rhs))))
+ && ((operand_equal_for_phi_arg_p (rhs2, cond_lhs)
+ && absorbing_element_p (code_def, cond_rhs, true))
+ || (operand_equal_for_phi_arg_p (rhs1, cond_lhs)
+ && absorbing_element_p (code_def, cond_rhs, false))))))
{
gsi = gsi_for_stmt (cond);
if (INTEGRAL_TYPE_P (TREE_TYPE (lhs)))
Index: gcc/testsuite/gcc.dg/pr24574.c
===================================================================
--- gcc/testsuite/gcc.dg/pr24574.c (revision 0)
+++ gcc/testsuite/gcc.dg/pr24574.c (working copy)
@@ -0,0 +1,36 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-phiopt1" } */
+
+int f0(int i)
+{
+ if (i == 0) return 0;
+ return i/10;
+}
+int f1(int i)
+{
+ return i?i/10:0;
+}
+
+int f2(int i)
+{
+ if (i == 0) return 0;
+ return i%10;
+}
+int f3(int i)
+{
+ return i?i%10:0;
+}
+
+int f4(int i)
+{
+ if (i == 0) return 0;
+ return i<<10;
+}
+int f5(int i)
+{
+ return i?i<<10:0;
+}
+
+/* We should if-convert all functions to carry out the operation
+ unconditionally. */
+/* { dg-final { scan-tree-dump-not "= PHI" "phiopt1" } } */
