Add the @nobarrier attribute to stop barriers from being added automatically to @inner loop blocks.

[kris-rowe]

Description

Closes #484

Introduces an attribute @nobarrier to disable the automatic addition of barriers after @inner loop blocks that write to shared memory.

Usage

@kernel void f(int N) 
{  
  @outer
  for(int i=0; i < N; ++i) {
    @shared double x[3];

    @inner @nobarrier
    for(int j=0; j < N; ++j) {
      x[j] = 1.0;
    }

    @inner
    for(int j=0; j < N; ++j) {
      x[j] = 1.0;
    }
  }
}

[codecov]

Codecov Report

Merging #544 (8e5401d) into main (1a4c374) will decrease coverage by 0.04%.
The diff coverage is 47.05%.

@@            Coverage Diff             @@
##             main     #544      +/-   ##
==========================================
- Coverage   76.40%   76.36%   -0.05%     
==========================================
  Files         261      262       +1     
  Lines       19510    19523      +13     
==========================================
+ Hits        14906    14908       +2     
- Misses       4604     4615      +11     

Impacted Files	Coverage Δ
...ca/internal/lang/builtins/attributes/noBarrier.cpp	30.76% <30.76%> (ø)
src/occa/internal/lang/modes/okl.cpp	93.12% <100.00%> (+0.03%)	⬆️
src/occa/internal/lang/modes/withLauncher.cpp	95.13% <100.00%> (+0.01%)	⬆️
src/occa/internal/lang/specialMacros.cpp	60.92% <0.00%> (-1.33%)	⬇️
src/occa/internal/utils/sys.cpp	76.62% <0.00%> (-0.11%)	⬇️