[LV] Introduce TTI::getMinimumVF

The function getMinimumVF(ElemWidth) will return the minimum VF for
a vector with elements of size ElemWidth bits. This value will only
apply to targets for which TTI::shouldMaximizeVectorBandwidth returns
true. The value of 0 indicates that there is no minimum VF.

Differential Revision: https://reviews.llvm.org/D45271

llvm-svn: 330062
diff --git a/llvm/lib/Analysis/TargetTransformInfo.cpp b/llvm/lib/Analysis/TargetTransformInfo.cpp
index 7744dbd..9843eed 100644
--- a/llvm/lib/Analysis/TargetTransformInfo.cpp
+++ b/llvm/lib/Analysis/TargetTransformInfo.cpp
@@ -344,6 +344,10 @@
   return TTIImpl->shouldMaximizeVectorBandwidth(OptSize);
 }
 
+unsigned TargetTransformInfo::getMinimumVF(unsigned ElemWidth) const {
+  return TTIImpl->getMinimumVF(ElemWidth);
+}
+
 bool TargetTransformInfo::shouldConsiderAddressTypePromotion(
     const Instruction &I, bool &AllowPromotionWithoutCommonHeader) const {
   return TTIImpl->shouldConsiderAddressTypePromotion(