Conditional schedules

• Add if statements to the scheduling language.
• Add a feature(...) function that can be used to test for whether a feature is enabled
  • For this to work, the scheduler needs to be run from a Cargo build script since it relies on testing environment variables (as described here).
• Modified matmul to use a single schedule testing for the "cuda" feature

juno_samples/matmul/src/cpu.sch

-macro optimize!(X) {
-  gvn(X);
-  phi-elim(X);
-  dce(X);
-  ip-sroa(X);
-  sroa(X);
-  dce(X);
-  gvn(X);
-  phi-elim(X);
-  dce(X);
-}
-
-macro codegen-prep!(X) {
-  optimize!(X);
-  gcm(X);
-  float-collections(X);
-  dce(X);
-  gcm(X);
-}
-
-macro forkify!(X) {
-  fixpoint {
-    forkify(X);
-    fork-guard-elim(X);
-  }
-}
-
-macro fork-tile![n](X) {
-  fork-tile[n, 0, false, true](X);
-}
-
-macro parallelize!(X) {
-  parallel-fork(X);
-  parallel-reduce(X);
-}
-
-macro unforkify!(X) {
-  fork-split(X);
-  unforkify(X);
-}
-
-optimize!(*);
-forkify!(*);
-associative(matmul@outer);
-
-// Parallelize by computing output array as 16 chunks
-let par = matmul@outer \ matmul@inner;
-fork-tile![4](par);
-let (outer, inner, _) = fork-reshape[[1, 3], [0], [2]](par);
-parallelize!(outer \ inner);
-
-let body = outline(inner);
-cpu(body);
-
-// Tile for cache, assuming 64B cache lines
-fork-tile![16](body);
-let (outer, inner) = fork-reshape[[0, 2, 4, 1, 3], [5]](body);
-
-reduce-slf(inner);
-unforkify!(body);
-codegen-prep!(*);