From: Andrew Pinski <apin...@marvell.com>
The problem here is tree-ssa-forwprop.c likes to produce
&MEM <const char *> [(void *)_4 + 152B] which is the same as
_4 p+ 152 which the rest of GCC likes better.
This implements this transformation back to pointer plus to
improve better code generation later on.
OK? Bootstrapped and tested on aarch64-linux-gnu.
Changes from v1:
* v2: Add comments.
gcc/ChangeLog:
PR tree-optimization/102216
* tree-ssa-forwprop.c (rewrite_assign_addr): New function.
(forward_propagate_addr_expr_1): Use rewrite_assign_addr
when rewriting into the addr_expr into an assignment.
gcc/testsuite/ChangeLog:
PR tree-optimization/102216
* g++.dg/tree-ssa/pr102216.C: New test.
---
gcc/testsuite/g++.dg/tree-ssa/pr102216.C | 22 +++++++++
gcc/tree-ssa-forwprop.c | 58 ++++++++++++++++++------
2 files changed, 67 insertions(+), 13 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/tree-ssa/pr102216.C
diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr102216.C
b/gcc/testsuite/g++.dg/tree-ssa/pr102216.C
new file mode 100644
index 00000000000..b903e4eb57d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/pr102216.C
@@ -0,0 +1,22 @@
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+void link_error ();
+void g ()
+{
+ const char **language_names;
+
+ language_names = new const char *[6];
+
+ const char **language_names_p = language_names;
+
+ language_names_p++;
+ language_names_p++;
+ language_names_p++;
+
+ if ( (language_names_p) - (language_names+3) != 0)
+ link_error();
+ delete[] language_names;
+}
+/* We should have removed the link_error on the gimple level as GCC should
+ be able to tell that language_names_p is the same as language_names+3. */
+/* { dg-final { scan-tree-dump-times "link_error" 0 "optimized" } } */
+
diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index a830bab78ba..e4331c60525 100644
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -637,6 +637,47 @@ forward_propagate_into_cond (gimple_stmt_iterator *gsi_p)
return 0;
}
+/* Rewrite the DEF_RHS as needed into the (plain) use statement. */
+
+static void
+rewrite_assign_addr (gimple_stmt_iterator *use_stmt_gsi, tree def_rhs)
+{
+ tree def_rhs_base;
+ poly_int64 def_rhs_offset;
+
+ /* Get the base and offset. */
+ if ((def_rhs_base = get_addr_base_and_unit_offset (TREE_OPERAND (def_rhs, 0),
+ &def_rhs_offset)))
+ {
+ tree new_ptr;
+ poly_offset_int off = 0;
+
+ /* If the base was a MEM, then add the offset to the other
+ offset and adjust the base. */
+ if (TREE_CODE (def_rhs_base) == MEM_REF)
+ {
+ off += mem_ref_offset (def_rhs_base);
+ new_ptr = TREE_OPERAND (def_rhs_base, 0);
+ }
+ else
+ new_ptr = build_fold_addr_expr (def_rhs_base);
+
+ /* If we have the new base is not an address express, then use a p+
expression
+ as the new expression instead of &MEM[x, offset]. */
+ if (TREE_CODE (new_ptr) != ADDR_EXPR)
+ {
+ tree offset = wide_int_to_tree (sizetype, off);
+ def_rhs = build2 (POINTER_PLUS_EXPR, TREE_TYPE (def_rhs), new_ptr,
offset);
+ }
+ }
+
+ /* Replace the rhs with the new expression. */
+ def_rhs = unshare_expr (def_rhs);
+ gimple_assign_set_rhs_from_tree (use_stmt_gsi, def_rhs);
+ gimple *use_stmt = gsi_stmt (*use_stmt_gsi);
+ update_stmt (use_stmt);
+}
+
/* We've just substituted an ADDR_EXPR into stmt. Update all the
relevant data structures to match. */
@@ -696,8 +737,8 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
if (single_use_p
&& useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs)))
{
- gimple_assign_set_rhs1 (use_stmt, unshare_expr (def_rhs));
- gimple_assign_set_rhs_code (use_stmt, TREE_CODE (def_rhs));
+ rewrite_assign_addr (use_stmt_gsi, def_rhs);
+ gcc_assert (gsi_stmt (*use_stmt_gsi) == use_stmt);
return true;
}
@@ -741,14 +782,7 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
if (forward_propagate_addr_expr (lhs, new_def_rhs, single_use_p))
return true;
- if (useless_type_conversion_p (TREE_TYPE (lhs),
- TREE_TYPE (new_def_rhs)))
- gimple_assign_set_rhs_with_ops (use_stmt_gsi, TREE_CODE (new_def_rhs),
- new_def_rhs);
- else if (is_gimple_min_invariant (new_def_rhs))
- gimple_assign_set_rhs_with_ops (use_stmt_gsi, NOP_EXPR, new_def_rhs);
- else
- return false;
+ rewrite_assign_addr (use_stmt_gsi, new_def_rhs);
gcc_assert (gsi_stmt (*use_stmt_gsi) == use_stmt);
update_stmt (use_stmt);
return true;
@@ -951,9 +985,7 @@ forward_propagate_addr_expr_1 (tree name, tree def_rhs,
unshare_expr (def_rhs),
fold_convert (ptr_type_node,
rhs2)));
- gimple_assign_set_rhs_from_tree (use_stmt_gsi, new_rhs);
- use_stmt = gsi_stmt (*use_stmt_gsi);
- update_stmt (use_stmt);
+ rewrite_assign_addr (use_stmt_gsi, new_rhs);
tidy_after_forward_propagate_addr (use_stmt);
return true;
}
--
2.17.1
