[Clang] Ensure vector predication loop metadata is always emitted when pragma is specified.

This patch ensures that vector predication and vectorization width
pragmas work together correctly/as expected. Specifically, this patch
fixes the issue that when vectorization_width > 1, the vector
predication behaviour (this would matter if it has NOT been disabled
explicitly by a pragma) was getting ignored, which was incorrect.

The fix here removes the dependence of vector predication on the
vectorization width. The loop metadata corresponding to clang loop
pragma vectorize_predicate is always emitted, if the pragma is
specified, even if vectorization is disabled by vectorize_width(1)
or vectorize(disable) since the option is also used for interleaving
by the LoopVectorize pass.

Reviewed By: dmgreen, Meinersbur

Differential Revision: https://reviews.llvm.org/D94779

1 files changed, 5 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGLoopInfo.cpp b/clang/lib/CodeGen/CGLoopInfo.cpp
index 8ba4059..12a6cd8 100644
--- a/clang/lib/CodeGen/CGLoopInfo.cpp
+++ b/clang/lib/CodeGen/CGLoopInfo.cpp
@@ -250,12 +250,10 @@ LoopInfo::createLoopVectorizeMetadata(const LoopAttributes &Attrs,
   Args.push_back(nullptr);
   Args.append(LoopProperties.begin(), LoopProperties.end());
 
-  // Setting vectorize.predicate
+  // Setting vectorize.predicate when it has been specified and vectorization
+  // has not been disabled.
   bool IsVectorPredicateEnabled = false;
-  if (Attrs.VectorizePredicateEnable != LoopAttributes::Unspecified &&
-      Attrs.VectorizeEnable != LoopAttributes::Disable &&
-      Attrs.VectorizeWidth < 1) {
-
+  if (Attrs.VectorizePredicateEnable != LoopAttributes::Unspecified) {
     IsVectorPredicateEnabled =
         (Attrs.VectorizePredicateEnable == LoopAttributes::Enable);
 
@@ -303,7 +301,8 @@ LoopInfo::createLoopVectorizeMetadata(const LoopAttributes &Attrs,
   //    explicitly requested fixed-width vectorization, i.e.
   //    vectorize.scalable.enable is false.
   if (Attrs.VectorizeEnable != LoopAttributes::Unspecified ||
-      IsVectorPredicateEnabled || Attrs.VectorizeWidth > 1 ||
+      (IsVectorPredicateEnabled && Attrs.VectorizeWidth != 1) ||
+      Attrs.VectorizeWidth > 1 ||
       Attrs.VectorizeScalable == LoopAttributes::Enable ||
       (Attrs.VectorizeScalable == LoopAttributes::Disable &&
        Attrs.VectorizeWidth != 1)) {