This patch adds support for two new variants of the vectorize_width
pragma:
1. vectorize_width(X[, fixed|scalable]) where an optional second
parameter is passed to the vectorize_width pragma, which indicates if
the user wishes to use fixed width or scalable vectorization. For
example the user can now write something like:
#pragma clang loop vectorize_width(4, fixed)
or
#pragma clang loop vectorize_width(4, scalable)
In the absence of a second parameter it is assumed the user wants
fixed width vectorization, in order to maintain compatibility with
existing code.
2. vectorize_width(fixed|scalable) where the width is left unspecified,
but the user hints what type of vectorization they prefer, either
fixed width or scalable.
I have implemented this by making use of the LLVM loop hint attribute:
llvm.loop.vectorize.scalable.enable
Tests were added to
clang/test/CodeGenCXX/pragma-loop.cpp
for both the 'fixed' and 'scalable' optional parameter.
See this thread for context: http://lists.llvm.org/pipermail/cfe-dev/2020-November/067262.html
Differential Revision: https://reviews.llvm.org/D89031
Since C++11, the C++ standard has a forward progress guarantee
[intro.progress], so all such functions must have the `mustprogress`
requirement. In addition, from C11 and onwards, loops without a non-zero
constant conditional or no conditional are also required to make
progress (C11 6.8.5p6). This patch implements these attribute deductions
so they can be used by the optimization passes.
Differential Revision: https://reviews.llvm.org/D86841
Let's try this again; this has been reverted/recommited a few times. Last time
this got reverted because for this loop:
void a() {
#pragma clang loop vectorize(disable)
for (;;)
;
}
vectorisation was incorrectly enabled and the vectorize.enable metadata was set
due to a logic error. But with this fixed, we now imply vectorisation when:
1) vectorisation is enabled, which means: VectorizeWidth > 1,
2) and don't want to add it when it is disabled or enabled, otherwise we would
be incorrectly setting it or duplicating the metadata, respectively.
This should fix PR27643.
Differential Revision: https://reviews.llvm.org/D69628
David Sherwood