f992ae4fd1
There's been a variation of the following in the code since 2005:
if (unoptimizable_true)
return;
use_this_symbol_to_force_linking(); // unreachable but never removed
Way back in 00d5508496c it was the win32 call `GetCurrentProcess`
but switched to `getenv("bar")` fairly soon after in 63e504ff43. While
that pulled in fewer dependencies and made the code portable, it's a
bit of a weird construct. The environment variable used for the `getenv`
call is "bar", which is particularly weird to see fly past when you run
`ltrace` on a binary linked against LLVM.
In this patch I don't try to replace this construct wholesale - it's
still required for architectural reasons I'm not able to tackle right
now, but I did try and make it slightly less weird and opaque:
- It gives the construct a name
- The environment variable hints where this comes from and that its
value is ignored
Combined, this should be a bit of improvement for the next person who
wonders what LLVM is up to when they trace their process or see
smatterings of `getenv("bar")` dotted around the source.
Polly - Polyhedral optimizations for LLVM ----------------------------------------- http://polly.llvm.org/ Polly uses a mathematical representation, the polyhedral model, to represent and transform loops and other control flow structures. Using an abstract representation it is possible to reason about transformations in a more general way and to use highly optimized linear programming libraries to figure out the optimal loop structure. These transformations can be used to do constant propagation through arrays, remove dead loop iterations, optimize loops for cache locality, optimize arrays, apply advanced automatic parallelization, drive vectorization, or they can be used to do software pipelining.