[Bitcode][Asm] Teach LLVM to read and write operand bundles.

[oota-llvm.git] / lib / Analysis / VectorUtils.cpp

diff --git a/lib/Analysis/VectorUtils.cpp b/lib/Analysis/VectorUtils.cpp
index 72140952ecb37d3c1b928ac91033f9f5451bdd37..93720857662f988a8e0a046cd10cdfeb7afbe165 100644 (file)
--- a/lib/Analysis/VectorUtils.cpp
+++ b/lib/Analysis/VectorUtils.cpp
@@ -18,6 +18,8 @@
 #include "llvm/IR/GetElementPtrTypeIterator.h"
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/IR/Value.h"
+#include "llvm/IR/Constants.h"
+
 using namespace llvm;
 using namespace llvm::PatternMatch;
 
@@ -406,3 +408,29 @@ Value *llvm::findScalarElement(Value *V, unsigned EltNo) {
   // Otherwise, we don't know.
   return nullptr;
 }
+
+/// \brief Get splat value if the input is a splat vector or return nullptr.
+/// This function is not fully general. It checks only 2 cases:
+/// the input value is (1) a splat constants vector or (2) a sequence
+/// of instructions that broadcast a single value into a vector.
+///
+llvm::Value *llvm::getSplatValue(Value *V) {
+  if (auto *CV = dyn_cast<ConstantDataVector>(V))
+    return CV->getSplatValue();
+
+  auto *ShuffleInst = dyn_cast<ShuffleVectorInst>(V);
+  if (!ShuffleInst)
+    return nullptr;
+  // All-zero (or undef) shuffle mask elements.
+  for (int MaskElt : ShuffleInst->getShuffleMask())
+    if (MaskElt != 0 && MaskElt != -1)
+      return nullptr;
+  // The first shuffle source is 'insertelement' with index 0.
+  auto *InsertEltInst =
+    dyn_cast<InsertElementInst>(ShuffleInst->getOperand(0));
+  if (!InsertEltInst || !isa<ConstantInt>(InsertEltInst->getOperand(2)) ||
+      !cast<ConstantInt>(InsertEltInst->getOperand(2))->isNullValue())
+    return nullptr;
+
+  return InsertEltInst->getOperand(1);
+}