Add new llvm.loop.unroll.enable metadata for use with "#pragma unroll".
This change adds the new unroll metadata "llvm.loop.unroll.enable" which directs
the optimizer to unroll a loop fully if the trip count is known at compile time, and
unroll partially if the trip count is not known at compile time. This differs from
"llvm.loop.unroll.full" which explicitly does not unroll a loop if the trip count is not
known at compile time
With this change "#pragma unroll" generates "llvm.loop.unroll.enable" rather than
"llvm.loop.unroll.full" metadata. This changes the semantics of "#pragma unroll" slightly
to mean "unroll aggressively (fully or partially)" rather than "unroll fully or not at all".
The motivating example for this change was some internal code with a loop marked
with "#pragma unroll" which only sometimes had a compile-time trip count depending
on template magic. When the trip count was a compile-time constant, everything works
as expected and the loop is fully unrolled. However, when the trip count was not a
compile-time constant the "#pragma unroll" explicitly disabled unrolling of the loop(!).
Removing "#pragma unroll" caused the loop to be unrolled partially which was desirable
from a performance perspective.
llvm-svn: 244467
diff --git a/clang/test/Parser/pragma-loop.cpp b/clang/test/Parser/pragma-loop.cpp
index 6082058..b9b5b41 100644
--- a/clang/test/Parser/pragma-loop.cpp
+++ b/clang/test/Parser/pragma-loop.cpp
@@ -132,7 +132,7 @@
/* expected-error {{missing argument; expected 'enable', 'assume_safety' or 'disable'}} */ #pragma clang loop vectorize()
/* expected-error {{missing argument; expected an integer value}} */ #pragma clang loop interleave_count()
-/* expected-error {{missing argument; expected 'full' or 'disable'}} */ #pragma clang loop unroll()
+/* expected-error {{missing argument; expected 'enable', 'full' or 'disable'}} */ #pragma clang loop unroll()
/* expected-error {{missing option; expected vectorize, vectorize_width, interleave, interleave_count, unroll, or unroll_count}} */ #pragma clang loop
/* expected-error {{invalid option 'badkeyword'}} */ #pragma clang loop badkeyword
@@ -186,7 +186,7 @@
/* expected-error {{invalid argument; expected 'enable', 'assume_safety' or 'disable'}} */ #pragma clang loop vectorize(badidentifier)
/* expected-error {{invalid argument; expected 'enable', 'assume_safety' or 'disable'}} */ #pragma clang loop interleave(badidentifier)
-/* expected-error {{invalid argument; expected 'full' or 'disable'}} */ #pragma clang loop unroll(badidentifier)
+/* expected-error {{invalid argument; expected 'enable', 'full' or 'disable'}} */ #pragma clang loop unroll(badidentifier)
while (i-7 < Length) {
List[i] = i;
}
@@ -195,7 +195,7 @@
// constants crash FE.
/* expected-error {{expected ')'}} */ #pragma clang loop vectorize(()
/* expected-error {{invalid argument; expected 'enable', 'assume_safety' or 'disable'}} */ #pragma clang loop interleave(*)
-/* expected-error {{invalid argument; expected 'full' or 'disable'}} */ #pragma clang loop unroll(=)
+/* expected-error {{invalid argument; expected 'enable', 'full' or 'disable'}} */ #pragma clang loop unroll(=)
/* expected-error {{type name requires a specifier or qualifier}} expected-error {{expected expression}} */ #pragma clang loop vectorize_width(^)
/* expected-error {{expected expression}} expected-error {{expected expression}} */ #pragma clang loop interleave_count(/)
/* expected-error {{expected expression}} expected-error {{expected expression}} */ #pragma clang loop unroll_count(==)