[SystemZ] Take better care when computing needed vector registers in TTI.

A new function getNumVectorRegs() is better to use for the number of needed
vector registers instead of getNumberOfParts(). This is to make sure that the
number of vector registers (and typically operations) required for a vector
type is accurate.

getNumberOfParts() which was previously used works by splitting the vector
type until it is legal gives incorrect results for types with a non
power of two number of elements (rare).

A new static function getScalarSizeInBits() that also checks for a pointer
type and returns 64U for it since otherwise it gets a value of 0). Used in a
few places where Ty may be pointer.

Review: Ulrich Weigand
llvm-svn: 344115

llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp

@@ -328,6 +328,25 @@ bool SystemZTTIImpl::hasDivRemOp(Type *DataType, bool IsSigned) {
   return (VT.isScalarInteger() && TLI->isTypeLegal(VT));
 }
 
+// Return the bit size for the scalar type or vector element
+// type. getScalarSizeInBits() returns 0 for a pointer type.
+static unsigned getScalarSizeInBits(Type *Ty) {
+  unsigned Size =
+    (Ty->isPtrOrPtrVectorTy() ? 64U : Ty->getScalarSizeInBits());
+  assert(Size > 0 && "Element must have non-zero size.");
+  return Size;
+}
+
+// getNumberOfParts() calls getTypeLegalizationCost() which splits the vector
+// type until it is legal. This would e.g. return 4 for <6 x i64>, instead of
+// 3.
+static unsigned getNumVectorRegs(Type *Ty) {
+  assert(Ty->isVectorTy() && "Expected vector type");
+  unsigned WideBits = getScalarSizeInBits(Ty) * Ty->getVectorNumElements();
+  assert(WideBits > 0 && "Could not compute size of vector");
+  return ((WideBits % 128U) ? ((WideBits / 128U) + 1) : (WideBits / 128U));
+}
+
 int SystemZTTIImpl::getArithmeticInstrCost(
     unsigned Opcode, Type *Ty,
     TTI::OperandValueKind Op1Info, TTI::OperandValueKind Op2Info,
@@ -370,7 +389,7 @@ int SystemZTTIImpl::getArithmeticInstrCost(
   if (Ty->isVectorTy()) {
     assert (ST->hasVector() && "getArithmeticInstrCost() called with vector type.");
     unsigned VF = Ty->getVectorNumElements();
-    unsigned NumVectors = getNumberOfParts(Ty);
+    unsigned NumVectors = getNumVectorRegs(Ty);
 
     // These vector operations are custom handled, but are still supported
     // with one instruction per vector, regardless of element size.
@@ -465,12 +484,11 @@ int SystemZTTIImpl::getArithmeticInstrCost(
                                        Opd1PropInfo, Opd2PropInfo, Args);
 }
 
-
 int SystemZTTIImpl::getShuffleCost(TTI::ShuffleKind Kind, Type *Tp, int Index,
                                    Type *SubTp) {
   assert (Tp->isVectorTy());
   assert (ST->hasVector() && "getShuffleCost() called.");
-  unsigned NumVectors = getNumberOfParts(Tp);
+  unsigned NumVectors = getNumVectorRegs(Tp);
 
   // TODO: Since fp32 is expanded, the shuffle cost should always be 0.
 
@@ -525,7 +543,7 @@ getVectorTruncCost(Type *SrcTy, Type *DstTy) {
 
   // TODO: Since fp32 is expanded, the extract cost should always be 0.
 
-  unsigned NumParts = getNumberOfParts(SrcTy);
+  unsigned NumParts = getNumVectorRegs(SrcTy);
   if (NumParts <= 2)
     // Up to 2 vector registers can be truncated efficiently with pack or
     // permute. The latter requires an immediate mask to be loaded, which
@@ -568,7 +586,7 @@ getVectorBitmaskConversionCost(Type *SrcTy, Type *DstTy) {
     // The bitmask will be truncated.
     PackCost = getVectorTruncCost(SrcTy, DstTy);
   else if (SrcScalarBits < DstScalarBits) {
-    unsigned DstNumParts = getNumberOfParts(DstTy);
+    unsigned DstNumParts = getNumVectorRegs(DstTy);
     // Each vector select needs its part of the bitmask unpacked.
     PackCost = Log2Diff * DstNumParts;
     // Extra cost for moving part of mask before unpacking.
@@ -613,8 +631,8 @@ int SystemZTTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src,
     assert (ST->hasVector() && "getCastInstrCost() called with vector type.");
     assert (Dst->isVectorTy());
     unsigned VF = Src->getVectorNumElements();
-    unsigned NumDstVectors = getNumberOfParts(Dst);
-    unsigned NumSrcVectors = getNumberOfParts(Src);
+    unsigned NumDstVectors = getNumVectorRegs(Dst);
+    unsigned NumSrcVectors = getNumVectorRegs(Src);
 
     if (Opcode == Instruction::Trunc) {
       if (Src->getScalarSizeInBits() == Dst->getScalarSizeInBits())
@@ -763,7 +781,7 @@ int SystemZTTIImpl::getCmpSelInstrCost(unsigned Opcode, Type *ValTy, Type *CondT
       // Float is handled with 2*vmr[lh]f + 2*vldeb + vfchdb for each pair of
       // floats.  FIXME: <2 x float> generates same code as <4 x float>.
       unsigned CmpCostPerVector = (ValTy->getScalarType()->isFloatTy() ? 10 : 1);
-      unsigned NumVecs_cmp = getNumberOfParts(ValTy);
+      unsigned NumVecs_cmp = getNumVectorRegs(ValTy);
 
       unsigned Cost = (NumVecs_cmp * (CmpCostPerVector + PredicateExtraCost));
       return Cost;
@@ -779,7 +797,7 @@ int SystemZTTIImpl::getCmpSelInstrCost(unsigned Opcode, Type *ValTy, Type *CondT
         PackCost =
           getVectorBitmaskConversionCost(CmpOpTy, ValTy);
 
-      return getNumberOfParts(ValTy) /*vsel*/ + PackCost;
+      return getNumVectorRegs(ValTy) /*vsel*/ + PackCost;
     }
   }
   else { // Scalar
@@ -808,7 +826,7 @@ getVectorInstrCost(unsigned Opcode, Type *Val, unsigned Index) {
     return ((Index % 2 == 0) ? 1 : 0);
 
   if (Opcode == Instruction::ExtractElement) {
-    int Cost = ((Val->getScalarSizeInBits() == 1) ? 2 /*+test-under-mask*/ : 1);
+    int Cost = ((getScalarSizeInBits(Val) == 1) ? 2 /*+test-under-mask*/ : 1);
 
     // Give a slight penalty for moving out of vector pipeline to FXU unit.
     if (Index == 0 && Val->isIntOrIntVectorTy())
@@ -828,7 +846,7 @@ int SystemZTTIImpl::getMemoryOpCost(unsigned Opcode, Type *Src,
   if (!Src->isVectorTy() && Opcode == Instruction::Load &&
       I != nullptr && I->hasOneUse()) {
       const Instruction *UserI = cast<Instruction>(*I->user_begin());
-      unsigned Bits = Src->getScalarSizeInBits();
+      unsigned Bits = getScalarSizeInBits(Src);
       bool FoldsLoad = false;
       switch (UserI->getOpcode()) {
       case Instruction::ICmp:
@@ -870,7 +888,8 @@ int SystemZTTIImpl::getMemoryOpCost(unsigned Opcode, Type *Src,
       }
   }
 
-  unsigned NumOps = getNumberOfParts(Src);
+  unsigned NumOps =
+    (Src->isVectorTy() ? getNumVectorRegs(Src) : getNumberOfParts(Src));
 
   if (Src->getScalarSizeInBits() == 128)
     // 128 bit scalars are held in a pair of two 64 bit registers.
@@ -887,11 +906,7 @@ int SystemZTTIImpl::getInterleavedMemoryOpCost(unsigned Opcode, Type *VecTy,
   assert(isa<VectorType>(VecTy) &&
          "Expect a vector type for interleaved memory op");
 
-  unsigned WideBits = (VecTy->isPtrOrPtrVectorTy() ?
-     (64U * VecTy->getVectorNumElements()) : VecTy->getPrimitiveSizeInBits());
-  assert (WideBits > 0 && "Could not compute size of vector");
-  int NumWideParts =
-    ((WideBits % 128U) ? ((WideBits / 128U) + 1) : (WideBits / 128U));
+  int NumWideParts = getNumVectorRegs(VecTy);
 
   // How many source vectors are handled to produce a vectorized operand?
   int NumElsPerVector = (VecTy->getVectorNumElements() / NumWideParts);

llvm/test/Analysis/CostModel/SystemZ/load-ptr-cmp-fold.ll

@@ -0,0 +1,11 @@
+; RUN: opt < %s -cost-model -analyze -mtriple=systemz-unknown -mcpu=z13 | FileCheck %s
+
+; Test that the cost heuristic for a folded load works also for a pointer operand.
+define void @fun0(i64* %lhs, i64** %rhs_ptr) {
+  %rhs = load i64*, i64** %rhs_ptr
+  %c = icmp eq i64* %lhs, %rhs
+  ret void
+; CHECK: Printing analysis 'Cost Model Analysis' for function 'fun0':
+; CHECK: Cost Model: Found an estimated cost of 0 for instruction:   %rhs = load
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction:   %c = icmp
+}

llvm/test/Analysis/CostModel/SystemZ/numvectorregs.ll

@@ -0,0 +1,10 @@
+; RUN: opt < %s -cost-model -analyze -mtriple=systemz-unknown -mcpu=z13 | FileCheck %s
+
+; Test that the cost for the number of vector registers is returned for a
+; non-power-of-two vector type.
+define <6 x double> @fun0(<6 x double> %lhs, <6 x double> %rhs) {
+  %a = fadd <6 x double> %lhs, %rhs
+  ret <6 x double> %a
+; CHECK: Printing analysis 'Cost Model Analysis' for function 'fun0':
+; CHECK: Cost Model: Found an estimated cost of 3 for instruction:   %a = fadd <6 x double>
+}