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[PATCH] More address forward propagation and ARRAY_REF re-construction
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Date: Mon, 6 Apr 2009 17:12:30 +0200 (CEST)
- Subject: [PATCH] More address forward propagation and ARRAY_REF re-construction
This patch makes sure we re-construct array accesses from
tmp_1 = &a[0] + off_1;
by folding such stmt during forwprop (and then possibly continuing
to propagate the result, &a[off'_2] in this case). To make this
work fold_stmt (or rather maybe_fold_stmt_addition) needs to handle
the above case in a similar way as forwprops
forward_propagate_addr_into_variable_array_index, so this patch
extends it to do that.
Together with this patch the next one I am about to send will
finally fix the C frontend oddity of creating non-GIMPLE &ARRAY
addresses.
I'm currently bootstrapping and testing both patches together
but will try this one alone and commit it if it succeeds.
Richard.
2009-04-06 Richard Guenther <rguenther@suse.de>
* tree-ssa-ccp.c (maybe_fold_stmt_addition): Move non-constant
indices into an array reference if possible.
* tree-ssa-forwprop.c (tree_ssa_forward_propagate_single_use_vars):
Fold POINTER_PLUS_EXPR statements with invariant address.
* gcc.dg/tree-ssa/ssa-ccp-25.c: New testcase.
* gcc.dg/tree-ssa/ssa-ccp-26.c: Likewise.
Index: gcc/tree-ssa-ccp.c
===================================================================
*** gcc/tree-ssa-ccp.c.orig 2009-04-06 16:17:46.000000000 +0200
--- gcc/tree-ssa-ccp.c 2009-04-06 16:17:55.000000000 +0200
*************** maybe_fold_stmt_addition (tree res_type,
*** 2094,2107 ****
tree ptd_type;
tree t;
- /* It had better be a constant. */
- if (TREE_CODE (op1) != INTEGER_CST)
- return NULL_TREE;
/* The first operand should be an ADDR_EXPR. */
if (TREE_CODE (op0) != ADDR_EXPR)
return NULL_TREE;
op0 = TREE_OPERAND (op0, 0);
/* If the first operand is an ARRAY_REF, expand it so that we can fold
the offset into it. */
while (TREE_CODE (op0) == ARRAY_REF)
--- 2094,2140 ----
tree ptd_type;
tree t;
/* The first operand should be an ADDR_EXPR. */
if (TREE_CODE (op0) != ADDR_EXPR)
return NULL_TREE;
op0 = TREE_OPERAND (op0, 0);
+ /* It had better be a constant. */
+ if (TREE_CODE (op1) != INTEGER_CST)
+ {
+ /* Or op0 should now be A[0] and the non-constant offset defined
+ via a multiplication by the array element size. */
+ if (TREE_CODE (op0) == ARRAY_REF
+ && integer_zerop (TREE_OPERAND (op0, 1))
+ && TREE_CODE (op1) == SSA_NAME
+ && host_integerp (TYPE_SIZE_UNIT (TREE_TYPE (op0)), 1))
+ {
+ gimple offset_def = SSA_NAME_DEF_STMT (op1);
+ if (!is_gimple_assign (offset_def))
+ return NULL_TREE;
+
+ if (gimple_assign_rhs_code (offset_def) == MULT_EXPR
+ && TREE_CODE (gimple_assign_rhs2 (offset_def)) == INTEGER_CST
+ && tree_int_cst_equal (gimple_assign_rhs2 (offset_def),
+ TYPE_SIZE_UNIT (TREE_TYPE (op0))))
+ return build1 (ADDR_EXPR, res_type,
+ build4 (ARRAY_REF, TREE_TYPE (op0),
+ TREE_OPERAND (op0, 0),
+ gimple_assign_rhs1 (offset_def),
+ TREE_OPERAND (op0, 2),
+ TREE_OPERAND (op0, 3)));
+ else if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (op0)))
+ && gimple_assign_rhs_code (offset_def) != MULT_EXPR)
+ return build1 (ADDR_EXPR, res_type,
+ build4 (ARRAY_REF, TREE_TYPE (op0),
+ TREE_OPERAND (op0, 0),
+ op1,
+ TREE_OPERAND (op0, 2),
+ TREE_OPERAND (op0, 3)));
+ }
+ return NULL_TREE;
+ }
+
/* If the first operand is an ARRAY_REF, expand it so that we can fold
the offset into it. */
while (TREE_CODE (op0) == ARRAY_REF)
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-25.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-25.c 2009-04-06 16:17:55.000000000 +0200
***************
*** 0 ****
--- 1,14 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-ccp1 -fdump-tree-forwprop1" } */
+
+ int a[256];
+ int foo(int i)
+ {
+ int *p = &a[0];
+ return *(p + i);
+ }
+
+ /* { dg-final { scan-tree-dump "&a\\\[D\\\." "ccp1" } } */
+ /* { dg-final { scan-tree-dump "= a\\\[D\\\." "forwprop1" } } */
+ /* { dg-final { cleanup-tree-dump "ccp1" } } */
+ /* { dg-final { cleanup-tree-dump "forwprop1" } } */
Index: gcc/tree-ssa-forwprop.c
===================================================================
*** gcc/tree-ssa-forwprop.c.orig 2009-04-06 16:18:15.000000000 +0200
--- gcc/tree-ssa-forwprop.c 2009-04-06 16:46:31.000000000 +0200
*************** tree_ssa_forward_propagate_single_use_va
*** 1256,1261 ****
--- 1256,1270 ----
else
gsi_next (&gsi);
}
+ else if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
+ && is_gimple_min_invariant (rhs))
+ {
+ /* Make sure to fold &a[0] + off_1 here. */
+ fold_stmt_inplace (stmt);
+ update_stmt (stmt);
+ if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
+ gsi_next (&gsi);
+ }
else if ((gimple_assign_rhs_code (stmt) == BIT_NOT_EXPR
|| gimple_assign_rhs_code (stmt) == NEGATE_EXPR)
&& TREE_CODE (rhs) == SSA_NAME)
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-26.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-26.c 2009-04-06 16:18:56.000000000 +0200
***************
*** 0 ****
--- 1,11 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-forwprop1" } */
+
+ int a[256];
+ int foo(int i)
+ {
+ return (a + 1)[i];
+ }
+
+ /* { dg-final { scan-tree-dump "= a\\\[D\\\." "forwprop1" } } */
+ /* { dg-final { cleanup-tree-dump "forwprop1" } } */