Answer by hanshenrik for Why don't modern compilers coalesce neighboring...
The first thing to understand is that f(const char buf[4]) does not guarantee that the pointer points to 4 elements, it means exactly the same as const char *buf, the 4 is completely ignored by the...
View ArticleAnswer by АлексейНеудачин for Why don't modern compilers coalesce neighboring...
There's the short-circuit evaluation thing. So it can't be optimized as you think. If buf[0] == 0 is falsebuf[1] == 0 must not be checked. It can be UB or something forbidden to use or whatever - this...
View ArticleAnswer by anatolyg for Why don't modern compilers coalesce neighboring memory...
If buf[0] is nonzero, the code will not access buf[1]. So the function should return false without checking the other buf elements. If buf is close to the end of the last memory page, buf[1] may...
View ArticleWhy don't modern compilers coalesce neighboring memory accesses?
Consider the following code:bool AllZeroes(const char buf[4]){ return buf[0] == 0 && buf[1] == 0 && buf[2] == 0 && buf[3] == 0;}Output assembly from Clang 13 with...
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