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
Specifying #pragma clang loop vectorize(assume_safety) on a loop adds the
mem.parallel_loop_access metadata to each load/store operation in the loop. This
metadata tells loop access analysis (LAA) to skip memory dependency checking.
llvm-svn: 239572
When pragma clang loop unroll() is specified without an argument the diagnostic message should inform that user that 'full' and 'disable' are valid arguments (not 'enable').
llvm-svn: 239363
Previously loop hints such as #pragma loop vectorize_width(#) required a constant. This patch allows a constant expression to be used as well. Such as a non-type template parameter or an expression (2 * c + 1).
Reviewed by Richard Smith
llvm-svn: 219589
This patch is necessary to support constant expressions which replaces the integer value in the loop hint attribute with an expression. The integer value was also storing the pragma’s state for options like vectorize(enable/disable) and the pragma unroll and nounroll directive. The state variable is introduced to hold the state of those options/pragmas. This moves the validation of the state (keywords) from SemaStmtAttr handler to the loop hint annotation token handler.
Resubmit with changes to try to fix the build-bot issue.
Reviewed by Aaron Ballman
llvm-svn: 214432
This patch is necessary to support constant expressions which replaces the integer value in the loop hint attribute with an expression. The integer value was also storing the pragma’s state for options like vectorize(enable/disable) and the pragma unroll and nounroll directive. The state variable is introduced to hold the state of those options/pragmas. This moves the validation of the state (keywords) from SemaStmtAttr handler to the loop hint annotation token handler.
Reviewed by Aaron Ballman
llvm-svn: 214333
This patch fixes a crash when handling malformed arguments to loop pragmas such
as: "#pragma clang loop vectorize(()". Essentially any argument which is not an
identifier or constant resulted in a crash. This patch also changes a couple of
the error messages which weren't quite correct. New behavior with this patch vs
old behavior:
#pragma clang loop vectorize(1)
OLD: error: missing keyword; expected 'enable' or 'disable'
NEW: error: invalid argument; expected 'enable' or 'disable'
#pragma clang loop vectorize()
OLD: error: expected ')'
NEW: error: missing argument to loop pragma 'vectorize'
#pragma clang loop vectorize_width(bad)
OLD: error: missing value; expected a positive integer value
NEW: error: invalid argument; expected a positive integer value
#pragma clang loop vectorize(bad)
OLD: invalid keyword 'bad'; expected 'enable' or 'disable'
NEW: error: invalid argument; expected 'enable' or 'disable'
http://reviews.llvm.org/D4197
Patch by Mark Heffernan
llvm-svn: 211292
Mark Heffernan