[ConstantFold][NFC] Compile time optimization for large vectors

Optimize the common case of splat vector constant. For large vector
going through all elements is expensive. For splatr/broadcast cases we
can skip going through all elements.

Differential Revision: https://reviews.llvm.org/D76664

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index bde4c07..e001b52 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -2891,7 +2891,7 @@ bool ConstantDataSequential::isCString() const {
   return Str.drop_back().find(0) == StringRef::npos;
 }
 
-bool ConstantDataVector::isSplat() const {
+bool ConstantDataVector::isSplatData() const {
   const char *Base = getRawDataValues().data();
 
   // Compare elements 1+ to the 0'th element.
@@ -2903,6 +2903,14 @@ bool ConstantDataVector::isSplat() const {
   return true;
 }
 
+bool ConstantDataVector::isSplat() const {
+  if (!IsSplatSet) {
+    IsSplatSet = true;
+    IsSplat = isSplatData();
+  }
+  return IsSplat;
+}
+
 Constant *ConstantDataVector::getSplatValue() const {
   // If they're all the same, return the 0th one as a representative.
   return isSplat() ? getElementAsConstant(0) : nullptr;