The following fixes PR63184 by using tree-affine to resolve pointer
comparisons. Instead of trying to stick this into a match.pd pattern
the following does this in the more constrained forwprop environment.
I've only implemented the cases where the comparison resolves to a
compile-time value, not the case where for example &a[i] < &a[j]
could be simplified to i < j. I'm not sure I can trust the
tree-affine machinery enough here to do that.
Both testcases require some CSE to happen thus the first forwprop
pass doesn't catch it.
Bootstrap & regtest running on x86_64-unknown-linux-gnu.
I'll collect some statistics from bootstrap.
Richard.
>From 79e88f7d31def4c49fe0b401e7fda408ef447710 Mon Sep 17 00:00:00 2001
From: Richard Guenther <rguent...@suse.de>
Date: Fri, 7 Dec 2018 10:47:07 +0100
Subject: [PATCH] fix-pr63184
2018-12-07 Richard Biener <rguent...@suse.de>
PR tree-optimization/63184
* tree-ssa-forwprop.c: Include tree-affine.h.
(ttacache): New global.
(forward_propagate_into_comparison_1): Use tree-affine to
resolve pointer comparisons.
(pass_forwprop::execute): Release ttacache.
* c-c++-common/pr19807-2.c: Remove XFAIL.
* c-c++-common/pr19807-3.c: Likewise.
diff --git a/gcc/testsuite/c-c++-common/pr19807-2.c
b/gcc/testsuite/c-c++-common/pr19807-2.c
index d2c010140d0..18949a9bc5a 100644
--- a/gcc/testsuite/c-c++-common/pr19807-2.c
+++ b/gcc/testsuite/c-c++-common/pr19807-2.c
@@ -1,6 +1,5 @@
-/* Some targets can optimize this on RTL. */
-/* { dg-do link { target { x86_64-*-* i?86-*-* } } } */
-/* { dg-options "-O -fdump-tree-optimized" } */
+/* { dg-do link } */
+/* { dg-options "-O -fdump-tree-forwprop2" } */
extern void link_error(void);
int i;
@@ -12,4 +11,4 @@ int main()
return 0;
}
-/* { dg-final { scan-tree-dump-not "link_error" "optimized" { xfail *-*-* } }
} */
+/* { dg-final { scan-tree-dump-not "link_error" "forwprop2" } } */
diff --git a/gcc/testsuite/c-c++-common/pr19807-3.c
b/gcc/testsuite/c-c++-common/pr19807-3.c
index bb7f9827725..f6a1531677f 100644
--- a/gcc/testsuite/c-c++-common/pr19807-3.c
+++ b/gcc/testsuite/c-c++-common/pr19807-3.c
@@ -1,6 +1,5 @@
-/* Some targets can optimize this on RTL. */
-/* { dg-do link { target { x86_64-*-* i?86-*-* } } } */
-/* { dg-options "-O -fdump-tree-optimized" } */
+/* { dg-do link } */
+/* { dg-options "-O -fdump-tree-forwprop2" } */
extern void link_error(void);
int i;
@@ -12,4 +11,4 @@ int main()
return 0;
}
-/* { dg-final { scan-tree-dump-not "link_error" "optimized" { xfail *-*-* } }
} */
+/* { dg-final { scan-tree-dump-not "link_error" "forwprop2" } } */
diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index 7449eaf86ae..08e41e2d85d 100644
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -48,6 +48,7 @@ along with GCC; see the file COPYING3. If not see
#include "optabs-tree.h"
#include "tree-vector-builder.h"
#include "vec-perm-indices.h"
+#include "tree-affine.h"
/* This pass propagates the RHS of assignment statements into use
sites of the LHS of the assignment. It's basically a specialized
@@ -184,6 +185,8 @@ static tree rhs_to_tree (tree type, gimple *stmt);
static bitmap to_purge;
+static hash_map<tree, name_expansion *> *ttacache;
+
/* Const-and-copy lattice. */
static vec<tree> lattice;
@@ -459,9 +462,72 @@ forward_propagate_into_comparison_1 (gimple *stmt,
/* If that wasn't successful either, try both operands. */
if (rhs0 != NULL_TREE
&& rhs1 != NULL_TREE)
- tmp = combine_cond_expr_cond (stmt, code, type,
- rhs0, rhs1,
- !(single_use0_p && single_use1_p));
+ {
+ tmp = combine_cond_expr_cond (stmt, code, type,
+ rhs0, rhs1,
+ !(single_use0_p && single_use1_p));
+ if (tmp)
+ return tmp;
+ }
+
+ /* When comparing two pointers try harder to resolve it by expanding
+ definitions (albeit not using our lattice) and looking at the
+ difference using the affine machinery. */
+ if (POINTER_TYPE_P (TREE_TYPE (op0))
+ && TREE_CODE (op0) == SSA_NAME
+ && TREE_CODE (op1) == SSA_NAME)
+ {
+ aff_tree aff0, aff1;
+ tree_to_aff_combination_expand (op0, TREE_TYPE (op0), &aff0, &ttacache);
+ tree_to_aff_combination_expand (op1, TREE_TYPE (op1), &aff1, &ttacache);
+ aff_combination_scale (&aff1, -1);
+ aff_combination_add (&aff0, &aff1);
+ if (aff_combination_const_p (&aff0))
+ {
+ /* Pointer difference is to be interpreted signed. */
+ poly_widest_int off = wi::sext (aff0.offset,
+ TYPE_PRECISION (TREE_TYPE (op0)));
+ if (known_eq (off, 0))
+ switch (code)
+ {
+ case EQ_EXPR:
+ case LE_EXPR:
+ case GE_EXPR:
+ return constant_boolean_node (true, type);
+ case NE_EXPR:
+ case LT_EXPR:
+ case GT_EXPR:
+ return constant_boolean_node (false, type);
+ default:;
+ }
+ else if (known_lt (off, 0))
+ switch (code)
+ {
+ case LT_EXPR:
+ case LE_EXPR:
+ case NE_EXPR:
+ return constant_boolean_node (true, type);
+ case EQ_EXPR:
+ case GE_EXPR:
+ case GT_EXPR:
+ return constant_boolean_node (false, type);
+ default:;
+ }
+ else if (known_gt (off, 0))
+ switch (code)
+ {
+ case LT_EXPR:
+ case LE_EXPR:
+ case NE_EXPR:
+ return constant_boolean_node (false, type);
+ case EQ_EXPR:
+ case GE_EXPR:
+ case GT_EXPR:
+ return constant_boolean_node (true, type);
+ default:;
+ }
+ }
+ }
return tmp;
}
@@ -2585,6 +2651,8 @@ pass_forwprop::execute (function *fun)
}
free (postorder);
lattice.release ();
+ delete ttacache;
+ ttacache = NULL;
/* Fixup stmts that became noreturn calls. This may require splitting
blocks and thus isn't possible during the walk. Do this
