From f315d1477d5164cb8ec1a004ce368dd52d47092a Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Mon, 11 May 2020 14:05:46 -0400 Subject: c++: Tweak VLA representation. If we put the SAVE_EXPR for a VLA size inside the MINUS_EXPR rather than outside, it will work better with constant folding. The equivalent change was made in the C front-end in 2004, in commit r0-64535-g8b0b9aefd29dfe6398857bcf5628662e2f0e21f6 gcc/cp/ChangeLog 2020-05-11 Jason Merrill * decl.c (compute_array_index_type_loc): Stabilize before building the MINUS_EXPR. --- gcc/cp/ChangeLog | 5 +++++ gcc/cp/decl.c | 14 +++++++++----- 2 files changed, 14 insertions(+), 5 deletions(-) diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index ab5e6abb866..9831c253668 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,8 @@ +2020-05-11 Jason Merrill + + * decl.c (compute_array_index_type_loc): Stabilize before building + the MINUS_EXPR. + 2020-05-11 Jason Merrill * decl.c (grokdeclarator): Adjust deprecated_state here. diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index adf94658420..dea1ba07c0e 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -10449,6 +10449,15 @@ compute_array_index_type_loc (location_t name_loc, tree name, tree size, itype = build_min (MINUS_EXPR, sizetype, size, integer_one_node); else { + if (!TREE_CONSTANT (size)) + { + /* A variable sized array. Arrange for the SAVE_EXPR on the inside + of the MINUS_EXPR, which allows the -1 to get folded with the +1 + that happens when building TYPE_SIZE. */ + size = variable_size (size); + stabilize_vla_size (size); + } + /* Compute the index of the largest element in the array. It is one less than the number of elements in the array. We save and restore PROCESSING_TEMPLATE_DECL so that computations in @@ -10466,11 +10475,6 @@ compute_array_index_type_loc (location_t name_loc, tree name, tree size, if (!TREE_CONSTANT (itype)) { - /* A variable sized array. */ - itype = variable_size (itype); - - stabilize_vla_size (itype); - if (sanitize_flags_p (SANITIZE_VLA) && current_function_decl != NULL_TREE) { -- cgit v1.2.3