This avoids using VLA types to initalize a register with
-ftrivial-auto-var-init in some cases.
Bootstrapped and tested on x86_64-unknown-linux-gnu, also tested on
the case riscv ICEd on.
Pushed.
2021-12-02 Richard Biener <rguent...@suse.de>
PR middle-end/103271
* internal-fn.c (expand_DEFERRED_INIT): When the base
of the LHS is a decl with matching constant size use
that as the initialization target instead of an
eventual VLA typed one.
---
gcc/internal-fn.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
index 6ac3460d538..08f94b7a17a 100644
--- a/gcc/internal-fn.c
+++ b/gcc/internal-fn.c
@@ -3050,6 +3050,23 @@ expand_DEFERRED_INIT (internal_fn, gcall *stmt)
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 this expands to a register and the underlying decl is wrapped in
+ a MEM_REF that just serves as an access type change expose the decl
+ if it is of correct size. This avoids a situation as in PR103271
+ if the target does not support a direct move to the registers mode. */
+ if (reg_lhs
+ && TREE_CODE (lhs_base) == MEM_REF
+ && TREE_CODE (TREE_OPERAND (lhs_base, 0)) == ADDR_EXPR
+ && DECL_P (TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0))
+ && integer_zerop (TREE_OPERAND (lhs_base, 1))
+ && tree_fits_uhwi_p (var_size)
+ && tree_int_cst_equal
+ (var_size,
+ DECL_SIZE_UNIT (TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0))))
+ {
+ lhs = TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0);
+ var_type = TREE_TYPE (lhs);
+ }
}
if (!reg_lhs)
--
2.31.1
