[InstCombine] fold bitcasts around an extractelement (3rd try)

[oota-llvm.git] / lib / Transforms / InstCombine / InstCombineCasts.cpp

diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 3cf8561a1d34f1a1cd78c31e03d3336ec0de37ec..dcd86db036b45080b965ed90e3df75677ff52b71 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1210,7 +1210,7 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) {
   if (Instruction *I = commonCastTransforms(CI))
     return I;
   // If we have fptrunc(OpI (fpextend x), (fpextend y)), we would like to
-  // simpilify this expression to avoid one or more of the trunc/extend
+  // simplify this expression to avoid one or more of the trunc/extend
   // operations if we can do so without changing the numerical results.
   //
   // The exact manner in which the widths of the operands interact to limit
@@ -1715,62 +1715,89 @@ static Value *optimizeIntegerToVectorInsertions(BitCastInst &CI,
   return Result;
 }
 
+/// Given a bitcasted source operand fed into an extract element instruction and
+/// then bitcasted again to a scalar type, eliminate at least one bitcast by
+/// changing the vector type of the extractelement instruction.
+/// Example:
+///   bitcast (extractelement (bitcast <2 x float> %X to <2 x i32>), 1) to float
+///    --->
+///   extractelement <2 x float> %X, i32 1
+static Instruction *foldBitCastExtElt(BitCastInst &BitCast, InstCombiner &IC,
+                                      const DataLayout &DL) {
+  Type *DestType = BitCast.getType();
+  if (DestType->isVectorTy())
+    return nullptr;
+
+  // TODO: Create and use a pattern matcher for ExtractElementInst.
+  auto *ExtElt = dyn_cast<ExtractElementInst>(BitCast.getOperand(0));
+  if (!ExtElt || !ExtElt->hasOneUse())
+    return nullptr;
+
+  Value *InnerBitCast = nullptr;
+  if (!match(ExtElt->getOperand(0), m_BitCast(m_Value(InnerBitCast))))
+    return nullptr;
+
+  // If the source is not a vector or its element type doesn't match the result
+  // type, bitcast it to a vector type that we can extract from.
+  Type *SourceType = InnerBitCast->getType();
+  if (SourceType->getScalarType() != DestType) {
+    unsigned VecWidth = SourceType->getPrimitiveSizeInBits();
+    unsigned DestWidth = DestType->getPrimitiveSizeInBits();
+    unsigned NumElts = VecWidth / DestWidth;
+    SourceType = VectorType::get(DestType, NumElts);
+    InnerBitCast = IC.Builder->CreateBitCast(InnerBitCast, SourceType, "bc");
+  }
+
+  return ExtractElementInst::Create(InnerBitCast, ExtElt->getOperand(1));
+}
+
+static Instruction *foldVecTruncToExtElt(Value *VecInput, Type *DestTy,
+                                         unsigned ShiftAmt, InstCombiner &IC,
+                                         const DataLayout &DL) {
+  VectorType *VecTy = cast<VectorType>(VecInput->getType());
+  unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
+  unsigned VecWidth = VecTy->getPrimitiveSizeInBits();
+
+  if ((VecWidth % DestWidth != 0) || (ShiftAmt % DestWidth != 0))
+    return nullptr;
+
+  // If the element type of the vector doesn't match the result type,
+  // bitcast it to be a vector type we can extract from.
+  unsigned NumVecElts = VecWidth / DestWidth;
+  if (VecTy->getElementType() != DestTy) {
+    VecTy = VectorType::get(DestTy, NumVecElts);
+    VecInput = IC.Builder->CreateBitCast(VecInput, VecTy);
+  }
+
+  unsigned Elt = ShiftAmt / DestWidth;
+  if (DL.isBigEndian())
+    Elt = NumVecElts - 1 - Elt;
+
+  return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
+}
 
 /// See if we can optimize an integer->float/double bitcast.
 /// The various long double bitcasts can't get in here.
 static Instruction *optimizeIntToFloatBitCast(BitCastInst &CI, InstCombiner &IC,
                                               const DataLayout &DL) {
   Value *Src = CI.getOperand(0);
-  Type *DestTy = CI.getType();
+  Type *DstTy = CI.getType();
 
   // If this is a bitcast from int to float, check to see if the int is an
   // extraction from a vector.
   Value *VecInput = nullptr;
   // bitcast(trunc(bitcast(somevector)))
   if (match(Src, m_Trunc(m_BitCast(m_Value(VecInput)))) &&
-      isa<VectorType>(VecInput->getType())) {
-    VectorType *VecTy = cast<VectorType>(VecInput->getType());
-    unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
-
-    if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0) {
-      // If the element type of the vector doesn't match the result type,
-      // bitcast it to be a vector type we can extract from.
-      if (VecTy->getElementType() != DestTy) {
-        VecTy = VectorType::get(DestTy,
-                                VecTy->getPrimitiveSizeInBits() / DestWidth);
-        VecInput = IC.Builder->CreateBitCast(VecInput, VecTy);
-      }
-
-      unsigned Elt = 0;
-      if (DL.isBigEndian())
-        Elt = VecTy->getPrimitiveSizeInBits() / DestWidth - 1;
-      return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
-    }
-  }
+      isa<VectorType>(VecInput->getType()))
+    return foldVecTruncToExtElt(VecInput, DstTy, 0, IC, DL);
 
   // bitcast(trunc(lshr(bitcast(somevector), cst))
   ConstantInt *ShAmt = nullptr;
   if (match(Src, m_Trunc(m_LShr(m_BitCast(m_Value(VecInput)),
                                 m_ConstantInt(ShAmt)))) &&
-      isa<VectorType>(VecInput->getType())) {
-    VectorType *VecTy = cast<VectorType>(VecInput->getType());
-    unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
-    if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0 &&
-        ShAmt->getZExtValue() % DestWidth == 0) {
-      // If the element type of the vector doesn't match the result type,
-      // bitcast it to be a vector type we can extract from.
-      if (VecTy->getElementType() != DestTy) {
-        VecTy = VectorType::get(DestTy,
-                                VecTy->getPrimitiveSizeInBits() / DestWidth);
-        VecInput = IC.Builder->CreateBitCast(VecInput, VecTy);
-      }
+      isa<VectorType>(VecInput->getType()))
+    return foldVecTruncToExtElt(VecInput, DstTy, ShAmt->getZExtValue(), IC, DL);
 
-      unsigned Elt = ShAmt->getZExtValue() / DestWidth;
-      if (DL.isBigEndian())
-        Elt = VecTy->getPrimitiveSizeInBits() / DestWidth - 1 - Elt;
-      return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
-    }
-  }
   return nullptr;
 }
 
@@ -1895,6 +1922,9 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     }
   }
 
+  if (Instruction *I = foldBitCastExtElt(CI, *this, DL))
+    return I;
+
   if (SrcTy->isPointerTy())
     return commonPointerCastTransforms(CI);
   return commonCastTransforms(CI);