[Bug tree-optimization/89296] New: tree copy-header masking uninitialized warning

[kugan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89296

            Bug ID: 89296
           Summary: tree copy-header masking uninitialized warning
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kugan at gcc dot gnu.org
  Target Milestone: ---

void test_func(void) {
  int loop;              // uninitialized and "garbage"
  while (!loop) {
       loop = get_a_value();  // <- must be for this test
       printk("...");
  }
}

from Linaro bug report https://bugs.linaro.org/show_bug.cgi?id=4134
-fno-tree-ch gets the required warning

diff --git a/gcc/tree-ssa-loop-ch.c b/gcc/tree-ssa-loop-ch.c
index c876d62..d405d00 100644
--- a/gcc/tree-ssa-loop-ch.c
+++ b/gcc/tree-ssa-loop-ch.c
@@ -393,7 +393,7 @@ ch_base::copy_headers (function *fun)
                {
                  gimple *stmt = gsi_stmt (bsi);
                  if (gimple_code (stmt) == GIMPLE_COND)
-                   gimple_set_no_warning (stmt, true);
+                   ;//gimple_set_no_warning (stmt, true);
                  else if (is_gimple_assign (stmt))
                    {
                      enum tree_code rhs_code = gimple_assign_rhs_code (stmt);

also gets the required warning. Looking into it.