Just something else I saw while analyzing dumps from an unrelated set of
changes.
It's relatively common to see sequences like this:
# parent_1 = PHI <parent_7(3), parent_6(D)(4), parent_6(D)(5)>
_11 = single_tree_10(D) != 0;
_12 = parent_1 == 0B;
_13 = _11 & _12;
if (_13 != 0)
goto <bb 8>;
else
goto <bb 7>;
Where VRP can deduce that the value of parent_6 has a nonzero value on
one (or more) of the paths reaching this block (because those paths
dereference parent_6).
Obviously when VRP knows parent_6 is nonzero, then we know the current
block will always transfer control to BB 7.
Or something like this:
<bb 6>:
# prephitmp_49 = PHI <1(4), pretmp_48(5)>
prev_line.31_6 = prev_line;
_8 = prev_line.31_6 != line_7(D);
line_differs_9 = (unsigned char) _8;
_10 = prephitmp_49 | line_differs_9;
if (_10 != 0)
goto <bb 8>;
else
goto <bb 7>;
We may not know the exact value of _10, but VRP can determine that when
BB6 is reached from BB4 that BB6 will always transfer control to BB8.
I never coded up the bits to utilize VRP information to simplify
statements for threading except for COND_EXPRs. It wasn't clear how
often it would be useful, thus I took the easy way out. This picks up a
hundred or so additional threading opportunities in my testfiles. Not
huge, but worth it IMHO.
Bootstrapped and regression tested on x86_64-unknown-linux-gnu.
Installed onto the trunk.
* tree-vrp.c (simplify_stmt_for_jump_threading): Try to
simplify assignments too. If the RHS collapses to a singleton
range, then return the value for the range.
* gcc.dg/tree-ssa/ssa-vrp-thread-1.c: New test.
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-vrp-thread-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/ssa-vrp-thread-1.c
new file mode 100644
index 0000000..9d9473e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-vrp-thread-1.c
@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp1-details" } */
+
+
+struct basic_block_def;
+typedef struct basic_block_def *basic_block;
+enum gimple_code
+{
+ LAST_AND_UNUSED_GIMPLE_CODE
+};
+struct omp_region
+{
+ struct omp_region *outer;
+ basic_block cont;
+};
+void
+build_omp_regions_1 (basic_block bb, struct omp_region *parent,
+ unsigned char single_tree, enum gimple_code code)
+{
+ if (code == 25)
+ parent = parent->outer;
+ else if (code == 42)
+ parent->cont = bb;
+ if (single_tree && !parent)
+ return;
+ oof ();
+}
+
+/* { dg-final { scan-tree-dump-times "Threaded" 1 "vrp1" } } */
+/* { dg-final { cleanup-tree-dump "vrp1" } } */
+
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index ec7ef8f..683a3db 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -9109,15 +9109,27 @@ static vec<tree> equiv_stack;
static tree
simplify_stmt_for_jump_threading (gimple stmt, gimple within_stmt)
{
- /* We only use VRP information to simplify conditionals. This is
- overly conservative, but it's unclear if doing more would be
- worth the compile time cost. */
- if (gimple_code (stmt) != GIMPLE_COND)
- return NULL;
+ if (gimple_code (stmt) == GIMPLE_COND)
+ return vrp_evaluate_conditional (gimple_cond_code (stmt),
+ gimple_cond_lhs (stmt),
+ gimple_cond_rhs (stmt), within_stmt);
+
+ if (gimple_code (stmt) == GIMPLE_ASSIGN)
+ {
+ value_range_t new_vr = VR_INITIALIZER;
+ tree lhs = gimple_assign_lhs (stmt);
+
+ if (TREE_CODE (lhs) == SSA_NAME
+ && (INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+ || POINTER_TYPE_P (TREE_TYPE (lhs))))
+ {
+ extract_range_from_assignment (&new_vr, stmt);
+ if (range_int_cst_singleton_p (&new_vr))
+ return new_vr.min;
+ }
+ }
- return vrp_evaluate_conditional (gimple_cond_code (stmt),
- gimple_cond_lhs (stmt),
- gimple_cond_rhs (stmt), within_stmt);
+ return NULL_TREE;
}
/* Blocks which have more than one predecessor and more than