Add LoadCombine pass.

This pass is disabled by default. Use -combine-loads to enable in -O[1-3]

Differential revision: http://reviews.llvm.org/D3580

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209791 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 32 insertions, 0 deletions

diff --git a/include/llvm/IR/IRBuilder.h b/include/llvm/IR/IRBuilder.h
index 580d333683..cedb87cdb7 100644
--- a/include/llvm/IR/IRBuilder.h
+++ b/include/llvm/IR/IRBuilder.h
@@ -1464,6 +1464,30 @@ public:
     Value *Zeros = ConstantAggregateZero::get(VectorType::get(I32Ty, NumElts));
     return CreateShuffleVector(V, Undef, Zeros, Name + ".splat");
   }
+
+  /// \brief Return a value that has been extracted from a larger integer type.
+  Value *CreateExtractInteger(const DataLayout &DL, Value *From,
+                              IntegerType *ExtractedTy, uint64_t Offset,
+                              const Twine &Name) {
+    IntegerType *IntTy = cast<IntegerType>(From->getType());
+    assert(DL.getTypeStoreSize(ExtractedTy) + Offset <=
+               DL.getTypeStoreSize(IntTy) &&
+           "Element extends past full value");
+    uint64_t ShAmt = 8 * Offset;
+    Value *V = From;
+    if (DL.isBigEndian())
+      ShAmt = 8 * (DL.getTypeStoreSize(IntTy) -
+                   DL.getTypeStoreSize(ExtractedTy) - Offset);
+    if (ShAmt) {
+      V = CreateLShr(V, ShAmt, Name + ".shift");
+    }
+    assert(ExtractedTy->getBitWidth() <= IntTy->getBitWidth() &&
+           "Cannot extract to a larger integer!");
+    if (ExtractedTy != IntTy) {
+      V = CreateTrunc(V, ExtractedTy, Name + ".trunc");
+    }
+    return V;
+  }
 };
 
 // Create wrappers for C Binding types (see CBindingWrapping.h).
diff --git a/include/llvm/InitializePasses.h b/include/llvm/InitializePasses.h
index 8e536159db..0466d11e35 100644
--- a/include/llvm/InitializePasses.h
+++ b/include/llvm/InitializePasses.h
@@ -272,6 +272,7 @@ void initializeSLPVectorizerPass(PassRegistry&);
 void initializeBBVectorizePass(PassRegistry&);
 void initializeMachineFunctionPrinterPassPass(PassRegistry&);
 void initializeStackMapLivenessPass(PassRegistry&);
+void initializeLoadCombinePass(PassRegistry&);
 }
 
 #endif
diff --git a/include/llvm/Transforms/Scalar.h b/include/llvm/Transforms/Scalar.h
index cf1d655440..8ecfd801d0 100644
--- a/include/llvm/Transforms/Scalar.h
+++ b/include/llvm/Transforms/Scalar.h
@@ -19,6 +19,7 @@
 
 namespace llvm {
 
+class BasicBlockPass;
 class FunctionPass;
 class Pass;
 class GetElementPtrInst;
@@ -381,6 +382,12 @@ FunctionPass *createAddDiscriminatorsPass();
 //
 FunctionPass *createSeparateConstOffsetFromGEPPass();
 
+//===----------------------------------------------------------------------===//
+//
+// LoadCombine - Combine loads into bigger loads.
+//
+BasicBlockPass *createLoadCombinePass();
+
 } // End llvm namespace
 
 #endif