Well, then you have moved the goal post, because initially you didn't ask for performance measurements, you asked for proof that compilers can optimize code better if they can assume signed arithmetic won't overflow.
And the blog post lists dozens of optimizations which can indeed be performed due to that decision.
The benefits of these optimizations will vary depending on the actual code and on the architecture/CPU, of course.
It will be greater for hot and tight loops that benefit from these optimizations and less important for cold parts of the code.
It will also be greater for more limited CPUs and less important for more sophisticated ones.
And the blog post lists dozens of optimizations which can indeed be performed due to that decision.
The benefits of these optimizations will vary depending on the actual code and on the architecture/CPU, of course.
It will be greater for hot and tight loops that benefit from these optimizations and less important for cold parts of the code.
It will also be greater for more limited CPUs and less important for more sophisticated ones.