https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89126
Kewen Lin <linkw at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |linkw at gcc dot gnu.org
--- Comment #4 from Kewen Lin <linkw at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #3)
> Eventually, after the function returns the inequality expression without a
> warning, c_parser_condition() calls c_fully_fold() on it which folds it into
> a constant, without a warning.
Happened to notice this PR when trying to answer the question [1]. The part
doing the folding is from match.pd.
/* Non-equality compare simplifications from fold_binary */
(for cmp (lt gt le ge)
/* Comparisons with the highest or lowest possible integer of
the specified precision will have known values. */
(simplify
(cmp (convert?@2 @0) uniform_integer_cst_p@1)
...
(if (wi::to_wide (cst) == max)
(switch
(if (cmp == GT_EXPR)
{ constant_boolean_node (false, type); })
(if (cmp == GE_EXPR)
(eq @2 @1))
(if (cmp == LE_EXPR)
{ constant_boolean_node (true, type); })
I noticed there are some warning support in match.pd like
fold_overflow_warning. Not sure whether we can add the similar supports there.
Probably hard to get LOC?
[1] https://gcc.gnu.org/pipermail/gcc-help/2021-January/139755.html
