no-warning overloading means we should be quite narrow to catch only
problematic cases when setting the flag.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2019-02-18 Richard Biener <rguent...@suse.de>
PR tree-optimization/89296
* tree-ssa-loop-ch.c (ch_base::copy_headers): Restrict setting
of no-warning flag to cases that might emit the bogus warning.
* gcc.dg/uninit-pr89296.c: New testcase.
Index: gcc/tree-ssa-loop-ch.c
===================================================================
--- gcc/tree-ssa-loop-ch.c (revision 268979)
+++ gcc/tree-ssa-loop-ch.c (working copy)
@@ -452,11 +452,23 @@ ch_base::copy_headers (function *fun)
{
gimple *stmt = gsi_stmt (bsi);
if (gimple_code (stmt) == GIMPLE_COND)
- gimple_set_no_warning (stmt, true);
+ {
+ tree lhs = gimple_cond_lhs (stmt);
+ if (gimple_cond_code (stmt) != EQ_EXPR
+ && gimple_cond_code (stmt) != NE_EXPR
+ && INTEGRAL_TYPE_P (TREE_TYPE (lhs))
+ && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (lhs)))
+ gimple_set_no_warning (stmt, true);
+ }
else if (is_gimple_assign (stmt))
{
enum tree_code rhs_code = gimple_assign_rhs_code (stmt);
- if (TREE_CODE_CLASS (rhs_code) == tcc_comparison)
+ tree rhs1 = gimple_assign_rhs1 (stmt);
+ if (TREE_CODE_CLASS (rhs_code) == tcc_comparison
+ && rhs_code != EQ_EXPR
+ && rhs_code != NE_EXPR
+ && INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
+ && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (rhs1)))
gimple_set_no_warning (stmt, true);
}
}
Index: gcc/testsuite/gcc.dg/uninit-pr89296.c
===================================================================
--- gcc/testsuite/gcc.dg/uninit-pr89296.c (nonexistent)
+++ gcc/testsuite/gcc.dg/uninit-pr89296.c (working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wuninitialized" } */
+
+int get_a_value ();
+void printk(const char *);
+void test_func()
+{
+ int loop;
+ while (!loop) { /* { dg-warning "is used uninitialized" } */
+ loop = get_a_value();
+ printk("...");
+ }
+}
