This PR shows an issue with ifcombine which ends up executing
stmts producing range info under a different condition than
before (always true). With a twisted enough maze we end up
miscompiling the testcase for this reason.
Thus the following patch which resets all flow-sensitive
info on defs in the affected block.
I chose this over disabling ifcombine on blocks with flow-sensitive
info and I didn't see an easy way to preserve some of it by analyzing
the condition we replace with true/false.
Bootstrap & regtest running on x86_64-unknown-linux-gnu.
Richard.
2015-07-22 Richard Biener <rguent...@suse.de>
PR tree-optimization/66952
* tree-ssa-ifcombine.c (pass_tree_ifcombine::execute): For
blocks we end up executing unconditionally reset all SSA
info such as range and alignment.
* tree-ssanames.h (reset_flow_sensitive_info): Declare.
* tree-ssanames.c (reset_flow_sensitive_info): New function.
* gcc.dg/torture/pr66952.c: New testcase.
Index: gcc/tree-ssa-ifcombine.c
===================================================================
--- gcc/tree-ssa-ifcombine.c (revision 226042)
+++ gcc/tree-ssa-ifcombine.c (working copy)
@@ -765,7 +765,22 @@ pass_tree_ifcombine::execute (function *
if (stmt
&& gimple_code (stmt) == GIMPLE_COND)
- cfg_changed |= tree_ssa_ifcombine_bb (bb);
+ if (tree_ssa_ifcombine_bb (bb))
+ {
+ /* Clear range info from all stmts in BB which is now executed
+ conditional on a always true/false condition. */
+ for (gimple_stmt_iterator gsi = gsi_start_bb (bb);
+ !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple stmt = gsi_stmt (gsi);
+ ssa_op_iter i;
+ tree op;
+ FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_DEF)
+ reset_flow_sensitive_info (op);
+ }
+
+ cfg_changed |= true;
+ }
}
free (bbs);
Index: gcc/tree-ssanames.c
===================================================================
--- gcc/tree-ssanames.c (revision 226042)
+++ gcc/tree-ssanames.c (working copy)
@@ -528,6 +528,23 @@ duplicate_ssa_name_fn (struct function *
}
+/* Reset all flow sensitive data on NAME such as range-info, nonzero
+ bits and alignment. */
+
+void
+reset_flow_sensitive_info (tree name)
+{
+ if (POINTER_TYPE_P (TREE_TYPE (name)))
+ {
+ /* points-to info is not flow-sensitive. */
+ if (SSA_NAME_PTR_INFO (name))
+ mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name));
+ }
+ else
+ SSA_NAME_RANGE_INFO (name) = NULL;
+}
+
+
/* Release all the SSA_NAMEs created by STMT. */
void
Index: gcc/tree-ssanames.h
===================================================================
--- gcc/tree-ssanames.h (revision 226042)
+++ gcc/tree-ssanames.h (working copy)
@@ -94,6 +94,7 @@ extern void duplicate_ssa_name_ptr_info
extern tree duplicate_ssa_name_fn (struct function *, tree, gimple);
extern void duplicate_ssa_name_range_info (tree, enum value_range_type,
struct range_info_def *);
+extern void reset_flow_sensitive_info (tree);
extern void release_defs (gimple);
extern void replace_ssa_name_symbol (tree, tree);
Index: gcc/testsuite/gcc.dg/torture/pr66952.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr66952.c (revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr66952.c (working copy)
@@ -0,0 +1,28 @@
+/* { dg-do run } */
+
+int a = 128, b;
+
+static int
+fn1 (char p1, int p2)
+{
+ return p1 < 0 || p1 > 1 >> p2 ? 0 : p1 << 1;
+}
+
+static int
+fn2 ()
+{
+ char c = a;
+ b = fn1 (c, 1);
+ if ((128 | c) < 0 ? 1 : 0)
+ return 1;
+ return 0;
+}
+
+int
+main ()
+{
+ if (fn2 () != 1)
+ __builtin_abort ();
+
+ return 0;
+}
