[Bug tree-optimization/127107] [17 Regression] long-multiple recogniser should not apply when widening_mul is not run

[konstantinos.eleftheriou at vrull dot eu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127107

--- Comment #1 from Konstantinos Eleftheriou <konstantinos.eleftheriou at vrull dot eu> ---
This is a known limitation. The comment on `optimize_widening_mul_active_p`
notes that "-fdisable-tree-widening_mul is not observed".
We allowed this based on the documentation saying, for the enable/disable
family of flags:
"These options are intended for use for debugging GCC.
Compiler users should use regular options for enabling/disabling
passes instead.".

FWIK there isn't any predicate to check for this before generating
the wide multiplication. Should we fix this in some way?