[ConstantRange][SimplifyCFG] Add a helper method to allow SimplifyCFG to determine if a ConstantRange has more than 8 elements without requiring an allocation if the ConstantRange is 64-bits wide.

Previously SimplifyCFG used getSetSize which returns an APInt that is 1 bit wider than the ConstantRange's bit width. In the reasonably common case that the ConstantRange is 64-bits wide, this requires returning a 65-bit APInt. APInt's can only store 64-bits without a memory allocation so this is inefficient.

The new method takes the 8 as an input and tells if the range contains more than that many elements without requiring any wider math.

llvm-svn: 302385

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 7a3e8b9ae91..b44bc74d655 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -596,7 +596,7 @@ private:
       Span = Span.inverse();
 
     // If there are a ton of values, we don't want to make a ginormous switch.
-    if (Span.getSetSize().ugt(8) || Span.isEmptySet()) {
+    if (Span.isSizeLargerThan(8) || Span.isEmptySet()) {
       return false;
     }