[InstCombine] fold trunc ([lshr] (bitcast vector) ) --> extractelement (PR25543)

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

diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index b90e4d846bc72e61da3a6fbdd0129fc059f485fe..2be3cdbee6be8badd980039188f468137363fc01 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -430,6 +430,50 @@ static bool canEvaluateTruncated(Value *V, Type *Ty, InstCombiner &IC,
   return false;
 }
 
   return false;
 }
 

+/// Given a vector that is bitcast to an integer, optionally logically
+/// right-shifted, and truncated, convert it to an extractelement.
+/// Example (big endian):
+///   trunc (lshr (bitcast <4 x i32> %X to i128), 32) to i32
+///   --->
+///   extractelement <4 x i32> %X, 1
+static Instruction *foldVecTruncToExtElt(TruncInst &Trunc, InstCombiner &IC,
+                                         const DataLayout &DL) {
+  Value *TruncOp = Trunc.getOperand(0);
+  Type *DestType = Trunc.getType();
+  if (!TruncOp->hasOneUse() || !isa<IntegerType>(DestType))
+    return nullptr;
+
+  Value *VecInput = nullptr;
+  ConstantInt *ShiftVal = nullptr;
+  if (!match(TruncOp, m_CombineOr(m_BitCast(m_Value(VecInput)),
+                                  m_LShr(m_BitCast(m_Value(VecInput)),
+                                         m_ConstantInt(ShiftVal)))) ||
+      !isa<VectorType>(VecInput->getType()))
+    return nullptr;
+
+  VectorType *VecType = cast<VectorType>(VecInput->getType());
+  unsigned VecWidth = VecType->getPrimitiveSizeInBits();
+  unsigned DestWidth = DestType->getPrimitiveSizeInBits();
+  unsigned ShiftAmount = ShiftVal ? ShiftVal->getZExtValue() : 0;
+
+  if ((VecWidth % DestWidth != 0) || (ShiftAmount % DestWidth != 0))
+    return nullptr;
+
+  // If the element type of the vector doesn't match the result type,
+  // bitcast it to a vector type that we can extract from.
+  unsigned NumVecElts = VecWidth / DestWidth;
+  if (VecType->getElementType() != DestType) {
+    VecType = VectorType::get(DestType, NumVecElts);
+    VecInput = IC.Builder->CreateBitCast(VecInput, VecType, "bc");
+  }
+
+  unsigned Elt = ShiftAmount / DestWidth;
+  if (DL.isBigEndian())
+    Elt = NumVecElts - 1 - Elt;
+
+  return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt));
+}
+

 Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
   if (Instruction *Result = commonCastTransforms(CI))
     return Result;
 Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
   if (Instruction *Result = commonCastTransforms(CI))
     return Result;


@@ -528,6 +572,9 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
                                      ConstantExpr::getTrunc(Cst, DestTy));
   }
 
                                      ConstantExpr::getTrunc(Cst, DestTy));
   }
 

+  if (Instruction *I = foldVecTruncToExtElt(CI, *this, DL))
+    return I;
+

   return nullptr;
 }
 
   return nullptr;
 }
 


@@ -1740,56 +1787,6 @@ static Instruction *canonicalizeBitCastExtElt(BitCastInst &BitCast,
   return ExtractElementInst::Create(NewBC, ExtElt->getIndexOperand());
 }
 
   return ExtractElementInst::Create(NewBC, ExtElt->getIndexOperand());
 }
 

-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 *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()))
-    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()))
-    return foldVecTruncToExtElt(VecInput, DstTy, ShAmt->getZExtValue(), IC, DL);
-
-  return nullptr;
-}
-

 Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
   // If the operands are integer typed then apply the integer transforms,
   // otherwise just apply the common ones.
 Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
   // If the operands are integer typed then apply the integer transforms,
   // otherwise just apply the common ones.


@@ -1833,11 +1830,6 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
     }
   }
 
     }
   }
 

-  // Try to optimize int -> float bitcasts.
-  if ((DestTy->isFloatTy() || DestTy->isDoubleTy()) && isa<IntegerType>(SrcTy))
-    if (Instruction *I = optimizeIntToFloatBitCast(CI, *this, DL))
-      return I;
-

   if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
     if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) {
       Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType());
   if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
     if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) {
       Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType());