[PATCH] D23354: [compiler-rt] Support dynamic shadow address instrumentation

[Kostya Serebryany via llvm-commits]

kcc added a comment.

All I've heard so far are very sad things, but they don't convince me. 
I believe we have Microsoft folks in the community now. Please summon some of them to this discussion.

We must find a way to use static shadow. 
My estimate is that dynamic shadow will cost us 10% in CPU and 5% in code size at the very least. 
These are just guesses, so benchmark results are more than welcome.

Comparing this change to whatever we do in the prologue is not correct since for dynamic shadow we
a) steal a register for the entire function
b) complicate the address arithmetic for every memory access.

BTW, why do we have to support all older windows versions? 
For me it would be fine to only support whatever the current version is and the future ones. 
At least as the first step.


https://reviews.llvm.org/D23354