Fix left shift operator undefined behavior in integer_ops

[joselopeqti]

As per the C++ Programming Reference page n0: 151, section: 7.6.7 Shift operators
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/n5001.pdf

The operands shall be prvalues of integral or unscoped enumeration type and integral promotions are performed. The type of the result is that of the promoted left operand. The behavior is undefined if the right operand is negative, or greater than or equal to the width of the promoted left operand.

[bashbaug]

Darn, I remember trying hard to avoid undefined behavior when we first did these tests (#1232), but I guess we missed this case.

Out of curiosity, how did you find this?

[bashbaug]

Could we do something like this? A bit more compact and easier to understand (IMHO):

Suggested change

	cl_ulong mask = 0;
	if (offset < 64)
	mask = (count < 64) ? ((1ULL << count) - 1) << offset : ~0ULL;
	cl_ulong shifted = 0;
	if (offset < 64) shifted = (insert << offset);
	cl_ulong result = (shifted & mask) | (base & ~mask);
	cl_ulong result = base;
	if (offset < 64)
	{
	cl_ulong mask = (count < 64) ? ((1ULL << count) - 1) << offset : ~0ULL;
	result = ((insert << offset) & mask) | (base & ~mask);
	}

I also considered this version with just the ternary operator also, but I think the version above with the single if statement is easier to understand.

    cl_ulong mask =
        (count < 64) && (offset < 64) ? ((1ULL << count) - 1) << offset : ~0ULL;
    cl_ulong result =
        (offset < 64) ? ((insert << offset) & mask) | (base & ~mask) : base;

[svenvh]

Out of curiosity, how did you find this?

On current main, I can reproduce the issue locally by compiling the CTS with -fsanitize=undefined.