On January 6, 2022 9:38:40 AM GMT+01:00, Jakub Jelinek via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>Hi!
>
>The threader changes resulted in a false positive warning during
>profiledbootstrap:
>In file included from ../../gcc/expr.c:26:
>../../gcc/tree.h: In function ‘rtx_def* expand_expr_real_1(tree, rtx,
>machine_mode, expand_modifier, rtx_def**, bool)’:
>../../gcc/tree.h:244:56: error: ‘context’ may be used uninitialized in this
>function [-Werror=maybe-uninitialized]
> 244 | #define TREE_CODE(NODE) ((enum tree_code) (NODE)->base.code)
> | ^~~~
>../../gcc/expr.c:10343:8: note: ‘context’ was declared here
>10343 | tree context;
> | ^~~~~~~
>While it will be nice to improve the uninit pass to handle it if possible
>(I do not want to close the PR until that is done), doing profiledbootstrap
>is a common thing to do, so a workaround is handy, especially as in this
>case when the workaround seems to be the right thing to do, as it moves
>a variable declaration to the only place where it is set and used and avoids
>the weird and for uninit asking
> tree context;
>...
> if (exp)
> context = ...;
> gcc_assert (!exp
> || use (context)
> || use_some_more (context));
>
>Bootstrapped/regtested on x86_64-linux and i686-linux with normal bootstrap
>and on aarch64-linux and powerpc64le-linux with profiledbootstrap, ok for
>trunk?
Ok.
Richard.
>2022-01-06 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/103899
> * expr.c (expand_expr_real_1): Add a workaround for bogus uninit
> warning by moving context variable to the only spot where it is used
> and moving gcc_assert into if body.
>
>--- gcc/expr.c.jj 2022-01-03 10:40:41.203164211 +0100
>+++ gcc/expr.c 2022-01-05 14:47:47.684660031 +0100
>@@ -10340,7 +10340,6 @@ expand_expr_real_1 (tree exp, rtx target
> enum tree_code code = TREE_CODE (exp);
> rtx subtarget, original_target;
> int ignore;
>- tree context;
> bool reduce_bit_field;
> location_t loc = EXPR_LOCATION (exp);
> struct separate_ops ops;
>@@ -10579,14 +10578,16 @@ expand_expr_real_1 (tree exp, rtx target
> /* Variables inherited from containing functions should have
> been lowered by this point. */
> if (exp)
>- context = decl_function_context (exp);
>- gcc_assert (!exp
>- || SCOPE_FILE_SCOPE_P (context)
>- || context == current_function_decl
>- || TREE_STATIC (exp)
>- || DECL_EXTERNAL (exp)
>- /* ??? C++ creates functions that are not TREE_STATIC. */
>- || TREE_CODE (exp) == FUNCTION_DECL);
>+ {
>+ tree context = decl_function_context (exp);
>+ gcc_assert (SCOPE_FILE_SCOPE_P (context)
>+ || context == current_function_decl
>+ || TREE_STATIC (exp)
>+ || DECL_EXTERNAL (exp)
>+ /* ??? C++ creates functions that are not
>+ TREE_STATIC. */
>+ || TREE_CODE (exp) == FUNCTION_DECL);
>+ }
>
> /* This is the case of an array whose size is to be determined
> from its initializer, while the initializer is still being parsed.
>
> Jakub
>
