On Sat, Nov 09, 2013 at 05:30:00PM +0100, Tom de Vries wrote:
>Richard,
>
>Consider the test-case test.c:
>...
>int z;
>int x;
>
>void
>f (int c, int d)
>{
> if (c)
> z = 5;
> else
> {
> if (d)
> x = 4;
> z = 5;
> }
>}
>...
>
>Atm, we don't tail-merge the 'z = 5' blocks, because gimple_equal_p
>returns false for the 'z = 5' statements. The relevant code is this:
>...
> if (TREE_CODE (lhs1) != SSA_NAME
> && TREE_CODE (lhs2) != SSA_NAME)
> return (vn_valueize (gimple_vdef (s1))
> == vn_valueize (gimple_vdef (s2)));
>...
>The vdefs of the 'z = 5' statements are different, because the
>incoming vuses are different.
>
>This patch handles GIMPLE_ASSIGNs with different vuse in
>gimple_equal_p, by doing a structural comparison.
>
>Bootstrapped and regtested on x86_64.
>
>OK for trunk?
>
>Thanks,
>- Tom
>
>2013-11-06 Tom de Vries <t...@codesourcery.com>
>
> * tree-ssa-tail-merge.c (gimple_equal_p): Add test for structural
> equality for GIMPLE_ASSIGN.
>
> * gcc.dg/tail-merge-store.c: New test.
>diff --git a/gcc/testsuite/gcc.dg/tail-merge-store.c
>b/gcc/testsuite/gcc.dg/tail-merge-store.c
>new file mode 100644
>index 0000000..1aefbdc
>--- /dev/null
>+++ b/gcc/testsuite/gcc.dg/tail-merge-store.c
>@@ -0,0 +1,22 @@
>+/* { dg-do compile } */
>+/* { dg-options "-O2 -ftree-tail-merge -fdump-tree-pre" } */
>+
>+int z;
>+int x;
>+
>+void
>+f (int c, int d)
>+{
>+ if (c)
>+ z = 5;
>+ else
>+ {
>+ if (d)
>+ x = 4;
>+ z = 5;
>+ }
>+}
>+
>+/* { dg-final { scan-tree-dump-times "duplicate of" 1 "pre"} } */
>+/* { dg-final { scan-tree-dump-times "z = 5" 1 "pre"} } */
>+/* { dg-final { cleanup-tree-dump "pre" } } */
>diff --git a/gcc/tree-ssa-tail-merge.c b/gcc/tree-ssa-tail-merge.c
>index 98b5882..43516a7 100644
>--- a/gcc/tree-ssa-tail-merge.c
>+++ b/gcc/tree-ssa-tail-merge.c
>@@ -1173,8 +1173,47 @@ gimple_equal_p (same_succ same_succ, gimple s1, gimple
>s2)
> lhs2 = gimple_get_lhs (s2);
> if (TREE_CODE (lhs1) != SSA_NAME
> && TREE_CODE (lhs2) != SSA_NAME)
>- return (vn_valueize (gimple_vdef (s1))
>- == vn_valueize (gimple_vdef (s2)));
>+ {
>+ /* If the vdef is the same, it's the same statement. */
>+ if (vn_valueize (gimple_vdef (s1))
>+ == vn_valueize (gimple_vdef (s2)))
>+ return true;
>+
>+ /* If the vdef is not the same but the vuse is the same, it's not the
>+ same stmt. */
>+ if (vn_valueize (gimple_vuse (s1))
>+ == vn_valueize (gimple_vuse (s2)))
>+ return false;
>+ /* If the vdef is not the same and the vuse is not the same, it might
>be
>+ same stmt. */
>+
>+ /* Test for structural equality. */
>+ if (gimple_assign_rhs_code (s1) != gimple_assign_rhs_code (s1)
typo, second one should be s2.
thanks,
>+ || (gimple_assign_nontemporal_move_p (s1)
>+ != gimple_assign_nontemporal_move_p (s2)))
>+ return false;
>+
>+ if (!operand_equal_p (lhs1, lhs2, 0))
>+ return false;
>+
>+ t1 = gimple_assign_rhs1 (s1);
>+ t2 = gimple_assign_rhs1 (s2);
>+ if (!gimple_operand_equal_value_p (t1, t2))
>+ return false;
>+
>+ t1 = gimple_assign_rhs2 (s1);
>+ t2 = gimple_assign_rhs2 (s2);
>+ if (!gimple_operand_equal_value_p (t1, t2))
>+ return false;
>+
>+ t1 = gimple_assign_rhs3 (s1);
>+ t2 = gimple_assign_rhs3 (s2);
>+ if (!gimple_operand_equal_value_p (t1, t2))
>+ return false;
>+
>+ /* Same structure. */
>+ return true;
>+ }
> else if (TREE_CODE (lhs1) == SSA_NAME
> && TREE_CODE (lhs2) == SSA_NAME)
> return vn_valueize (lhs1) == vn_valueize (lhs2);
