[committed][PR tree-optimization/114277] Fix missed optimization for...

[committed][PR tree-optimization/114277] Fix missed optimization for multiplication against boolean value

Andrew, Raphael and I have all poked at it in various ways over the last year
or so.  I think when Raphael and I first looked at it I sent us down a bit of
rathole.

In particular it's odd that we're using a multiply to implement a select and it
seemed like recognizing the idiom and rewriting into a conditional move was the
right path.  That looked reasonably good for the test, but runs into problems
with min/max detection elsewhere.

I think that initial investigation somewhat polluted our thinking.  The
regression can be fixed with a fairly simple match.pd pattern.

Essentially we want to handle

x * (x || b) -> x
x * !(x || b) -> 0

There's simplifications that can be made for "&&" cases, but I haven't seen
them in practice.  Rather than drop in untested patterns, I'm leaving that as a
future todo.

My original was two match.pd patterns.  Andrew combined them into a single
pattern.  I've made this conditional on GIMPLE as an earlier version that
simplified to a conditional move showed that when applied on GENERIC we could
drop an operand with a side effect which is clearly not good.

I've bootstrapped and regression tested this on x86.  I've also tested on the
various embedded targets in my tester.

	PR tree-optimization/114277
gcc/
	* match.pd (a * (a || b) -> a): New pattern.
	(a * !(a || b) -> 0): Likewise.

gcc/testsuite
	* gcc.target/i386/pr114277.c: New test.
	* gcc.target/riscv/pr114277.c: Likewise.

	Co-author:  Andrew Pinski <quic_apinski@quicinc.com>