Displaying 2 results from an estimated 2 matches for "add_two_globals".
2015 Nov 03
3
[RFC] A new intrinsic, `llvm.blackbox`, to explicitly prevent constprop, die, etc optimizations
...u're trying to measure.
Common alternate approaches are to use a volatile store (so that it
can't be eliminated or sunk out of loops) or a call to an external
function with a cheap calling convention.
As an example:
int a = 5; // initialization is not visible to compiler
int b = 7;
void add_two_globals()
sink(a+b)
}
If what I'm look into is the code generation around addition, this is a
very useful way of testing the entire compiler - frontend, middle end,
and backend.
I'll note that we use such a framework extensively.
What I'm not clear on is why this needs to be an intrinsi...
2015 Nov 03
3
[RFC] A new intrinsic, `llvm.blackbox`, to explicitly prevent constprop, die, etc optimizations
On Mon, Nov 2, 2015 at 7:19 PM, Sanjoy Das <sanjoy at playingwithpointers.com>
wrote:
> Why does this need to be an intrinsic (as opposed to generic "unknown
> function" to llvm)?
>
> Secondly, have you looked into a volatile store / load to an alloca? That
> should work with PNaCl and WebAssembly.
>
> E.g.
>
> define i32 @blackbox(i32 %arg) {
>