This refines the way we figure whether we are facing a register
that cannot be initialized by emitting a memset away from inspecting
expanded RTL of the LHS to using the predicates expand_assignment
is using to detect decls or MEM_REFs with non-memory DECL_RTL.
Bootstrapped and tested on x86_64-unknown-linux-gnu, I'm double-checking
the testsuite with -ftrivial-auto-var-init=zero right now.
Richard.
2021-10-04 Richard Biener <rguent...@suse.de>
* expr.h (non_mem_decl_p): Declare.
(mem_ref_refers_to_non_mem_p): Likewise.
* expr.c (non_mem_decl_p): Export.
(mem_ref_refers_to_non_mem_p): Likewise.
* internal-fn.c (expand_DEFERRED_INIT): Do not expand the LHS
but check the base with mem_ref_refers_to_non_mem_p
and non_mem_decl_p.
* c-c++-common/pr102285.c: New testcase.
---
gcc/expr.c | 4 ++--
gcc/expr.h | 3 +++
gcc/internal-fn.c | 7 +++++--
gcc/testsuite/c-c++-common/pr102285.c | 10 ++++++++++
4 files changed, 20 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/c-c++-common/pr102285.c
diff --git a/gcc/expr.c b/gcc/expr.c
index e0bcbccd905..eb33643bd77 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -5305,7 +5305,7 @@ get_bit_range (poly_uint64_pod *bitstart, poly_uint64_pod
*bitend, tree exp,
has non-BLKmode. DECL_RTL must not be a MEM; if
DECL_RTL was not set yet, return false. */
-static inline bool
+bool
non_mem_decl_p (tree base)
{
if (!DECL_P (base)
@@ -5322,7 +5322,7 @@ non_mem_decl_p (tree base)
/* Returns true if REF refers to an object that does not
reside in memory and has non-BLKmode. */
-static inline bool
+bool
mem_ref_refers_to_non_mem_p (tree ref)
{
tree base;
diff --git a/gcc/expr.h b/gcc/expr.h
index 94a85b40dca..890ec19ac7e 100644
--- a/gcc/expr.h
+++ b/gcc/expr.h
@@ -346,4 +346,7 @@ extern void expand_operands (tree, tree, rtx, rtx*, rtx*,
/* Return an rtx for the size in bytes of the value of an expr. */
extern rtx expr_size (tree);
+extern bool mem_ref_refers_to_non_mem_p (tree);
+extern bool non_mem_decl_p (tree);
+
#endif /* GCC_EXPR_H */
diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
index ef5dc90db56..110145218b9 100644
--- a/gcc/internal-fn.c
+++ b/gcc/internal-fn.c
@@ -3015,8 +3015,11 @@ expand_DEFERRED_INIT (internal_fn, gcall *stmt)
reg_lhs = true;
else
{
- rtx tem = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
- reg_lhs = !MEM_P (tem);
+ tree lhs_base = lhs;
+ while (handled_component_p (lhs_base))
+ lhs_base = TREE_OPERAND (lhs_base, 0);
+ reg_lhs = (mem_ref_refers_to_non_mem_p (lhs_base)
+ || non_mem_decl_p (lhs_base));
}
if (!reg_lhs)
diff --git a/gcc/testsuite/c-c++-common/pr102285.c
b/gcc/testsuite/c-c++-common/pr102285.c
new file mode 100644
index 00000000000..644054ba585
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr102285.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O -ftrivial-auto-var-init=zero -Wuninitialized" } */
+
+int
+qy (void)
+{
+ int tw = 4;
+ int fb[tw];
+ return fb[2]; /* { dg-warning "uninitialized" } */
+}
--
2.31.1
