This turns out to be far easier than expected. Given a conditional like
x == y, we already record the canonicalized x = y equivalence. If we
just record y = x then this "just works".
The only tricky thing is the following of the SSA_NAME_VALUE chain for
the source argument -- we need to avoid that when recording the y = x
variant (since following x's value chain would lead back to y). That's
easily resolved with an _raw variant which doesn't follow the source
value chain.
While working through the code, I saw the old comment WRT loop depth and
PR 61757 in record_equality. With the code to follow backedges in the
CFG gone from the old threader, that code is no longer needed. So I
removed it, restoring Richi's cleanup work from early 2015.
Bootstrapped & regression tested on x86-linux. Installed on the trunk.
Jeff
commit 122fa7e277f132dcfef5d66378f7ef3411ae8b84
Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Mon Feb 8 08:17:32 2016 +0000
PR tree-optimization/65917
* tree-ssa-dom.c (record_temporary_equivalences): Record both
equivalences from if (x == y) style conditionals.
(loop_depth_of_name): Remove.
(record_equality): Remove loop depth check.
* tree-ssa-scopedtables.h (const_and_copies): Refine comments.
(const_and_copies::record_const_or_copy_raw): New member function.
* tree-ssa-scopedtables.c
(const_and_copies::record_const_or_copy_raw): New, factored out of
(const_and_copies::record_const_or_copy): Call new member function.
PR tree-optimization/65917
* gcc.dg/tree-ssa/20030922-2.c: No longer xfailed.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@233207
138bc75d-0d04-0410-961f-82ee72b054a4
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a465156..2c4a8b6 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,17 @@
+2016-02-08 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/65917
+ * tree-ssa-dom.c (record_temporary_equivalences): Record both
+ equivalences from if (x == y) style conditionals.
+ (loop_depth_of_name): Remove.
+ (record_equality): Remove loop depth check.
+ * tree-ssa-scopedtables.h (const_and_copies): Refine comments.
+ (const_and_copies::record_const_or_copy_raw): New member function.
+ * tree-ssa-scopedtables.c
+ (const_and_copies::record_const_or_copy_raw): New, factored out of
+ (const_and_copies::record_const_or_copy): Call new member function.
+
+
2016-02-05 Jeff Law <l...@redhat.com>
PR tree-optimization/68541
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8d3438e..6940136 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-08 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/65917
+ * gcc.dg/tree-ssa/20030922-2.c: No longer xfailed.
+
2016-02-07 Jerry DeLisle <jvdeli...@gcc.gnu.org>
PR fortran/50555
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/20030922-2.c
b/gcc/testsuite/gcc.dg/tree-ssa/20030922-2.c
index 6c133bd..16c79da 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/20030922-2.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/20030922-2.c
@@ -20,8 +20,4 @@ rgn_rank (rtx insn1, rtx insn2)
}
/* There should be two IF conditionals. */
-/* This now fails as it requires a very specific decision of DOM which
- SSA name to record as a copy of the other when DOM derives copies
- from temporary equivalences. The heuristics there no longer do
- the correct thing. VRP still optimizes this testcase. */
-/* { dg-final { scan-tree-dump-times "if " 2 "dom2" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "if " 2 "dom2" } } */
diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index b690d92..f44ac13 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -917,6 +917,15 @@ record_temporary_equivalences (edge e,
tree rhs = edge_info->rhs;
record_equality (lhs, rhs, const_and_copies);
+ /* We already recorded that LHS = RHS, with canonicalization,
+ value chain following, etc.
+
+ We also want to return RHS = LHS, but without any canonicalization
+ or value chain following. */
+ if (TREE_CODE (rhs) == SSA_NAME)
+ const_and_copies->record_const_or_copy_raw (rhs, lhs,
+ SSA_NAME_VALUE (rhs));
+
/* If LHS is an SSA_NAME and RHS is a constant integer and LHS was
set via a widening type conversion, then we may be able to record
additional equivalences. */
@@ -1161,33 +1170,6 @@ record_cond (cond_equivalence *p,
delete element;
}
-/* Return the loop depth of the basic block of the defining statement of X.
- This number should not be treated as absolutely correct because the loop
- information may not be completely up-to-date when dom runs. However, it
- will be relatively correct, and as more passes are taught to keep loop info
- up to date, the result will become more and more accurate. */
-
-static int
-loop_depth_of_name (tree x)
-{
- gimple *defstmt;
- basic_block defbb;
-
- /* If it's not an SSA_NAME, we have no clue where the definition is. */
- if (TREE_CODE (x) != SSA_NAME)
- return 0;
-
- /* Otherwise return the loop depth of the defining statement's bb.
- Note that there may not actually be a bb for this statement, if the
- ssa_name is live on entry. */
- defstmt = SSA_NAME_DEF_STMT (x);
- defbb = gimple_bb (defstmt);
- if (!defbb)
- return 0;
-
- return bb_loop_depth (defbb);
-}
-
/* Similarly, but assume that X and Y are the two operands of an EQ_EXPR.
This constrains the cases in which we may treat this as assignment. */
@@ -1224,10 +1206,7 @@ record_equality (tree x, tree y, class const_and_copies
*const_and_copies)
long as we canonicalize on one value. */
if (is_gimple_min_invariant (y))
;
- else if (is_gimple_min_invariant (x)
- /* ??? When threading over backedges the following is important
- for correctness. See PR61757. */
- || (loop_depth_of_name (x) < loop_depth_of_name (y)))
+ else if (is_gimple_min_invariant (x))
prev_x = x, x = y, y = prev_x, prev_x = prev_y;
else if (prev_x && is_gimple_min_invariant (prev_x))
x = y, y = prev_x, prev_x = prev_y;
diff --git a/gcc/tree-ssa-scopedtables.c b/gcc/tree-ssa-scopedtables.c
index 613f50b..b18978e 100644
--- a/gcc/tree-ssa-scopedtables.c
+++ b/gcc/tree-ssa-scopedtables.c
@@ -700,6 +700,28 @@ const_and_copies::pop_to_marker (void)
}
}
+/* Record that X has the value Y and that X's previous value is PREV_X.
+
+ This variant does not follow the value chain for Y. */
+
+void
+const_and_copies::record_const_or_copy_raw (tree x, tree y, tree prev_x)
+{
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "0>>> COPY ");
+ print_generic_expr (dump_file, x, 0);
+ fprintf (dump_file, " = ");
+ print_generic_expr (dump_file, y, 0);
+ fprintf (dump_file, "\n");
+ }
+
+ set_ssa_name_value (x, y);
+ m_stack.reserve (2);
+ m_stack.quick_push (prev_x);
+ m_stack.quick_push (x);
+}
+
/* Record that X has the value Y. */
void
@@ -708,7 +730,9 @@ const_and_copies::record_const_or_copy (tree x, tree y)
record_const_or_copy (x, y, SSA_NAME_VALUE (x));
}
-/* Record that X has the value Y and that X's previous value is PREV_X. */
+/* Record that X has the value Y and that X's previous value is PREV_X.
+
+ This variant follow's Y value chain. */
void
const_and_copies::record_const_or_copy (tree x, tree y, tree prev_x)
@@ -720,19 +744,7 @@ const_and_copies::record_const_or_copy (tree x, tree y,
tree prev_x)
y = tmp ? tmp : y;
}
- if (dump_file && (dump_flags & TDF_DETAILS))
- {
- fprintf (dump_file, "0>>> COPY ");
- print_generic_expr (dump_file, x, 0);
- fprintf (dump_file, " = ");
- print_generic_expr (dump_file, y, 0);
- fprintf (dump_file, "\n");
- }
-
- set_ssa_name_value (x, y);
- m_stack.reserve (2);
- m_stack.quick_push (prev_x);
- m_stack.quick_push (x);
+ record_const_or_copy_raw (x, y, prev_x);
}
bool
diff --git a/gcc/tree-ssa-scopedtables.h b/gcc/tree-ssa-scopedtables.h
index 30f92d8..c933821 100644
--- a/gcc/tree-ssa-scopedtables.h
+++ b/gcc/tree-ssa-scopedtables.h
@@ -161,11 +161,18 @@ class const_and_copies
was pushed. */
void pop_to_marker (void);
- /* Record a single const/copy pair that can be unwound. */
+ /* Record a single const/copy pair that can be unwound. This version
+ may follow the value chain for the RHS. */
void record_const_or_copy (tree, tree);
+ /* Record a single const/copy pair that can be unwound. This version
+ does not follow the value chain for the RHS. */
+ void record_const_or_copy_raw (tree, tree, tree);
+
/* Special entry point when we want to provide an explicit previous
- value for the first argument. Try to get rid of this in the future. */
+ value for the first argument. Try to get rid of this in the future.
+
+ This version may also follow the value chain for the RHS. */
void record_const_or_copy (tree, tree, tree);
private:
