Optimize combination of comparisons to dec+compare

Optimize combination of comparisons to dec+compare

This patch adds patterns for optimizing
x < y || y == XXX_MIN to x <= y-1
x >= y && y != XXX_MIN to x > y-1
if y is an integer with TYPE_OVERFLOW_WRAPS.

This fixes pr96674.

Tested on x86_64-pc-linux-gnu.

For this function

bool f(unsigned a, unsigned b)
{
    return (b == 0) | (a < b);
}

the code without the patch is

test   esi,esi
sete   al
cmp    esi,edi
seta   dl
or     eax,edx
ret

the code with the patch is

sub    esi,0x1
cmp    esi,edi
setae  al
ret

	PR tree-optimization/96674
gcc/
	* match.pd: New patterns: x < y || y == XXX_MIN --> x <= y - 1
	x >= y && y != XXX_MIN --> x > y - 1

gcc/testsuite
	* gcc.dg/pr96674.c: New tests.