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Handle more instruction types when flattening offset vectors.

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Generalize the lScalarizeVector() utility routine (used in determining
when we can change gathers/scatters into vector loads/stores, respectively)
to handle vector shuffles and vector loads.  This fixes issue #79, which
provided a case where a gather was being performed even though a vector
load was possible.
This commit is contained in:
Matt Pharr
2011-09-13 09:43:56 -07:00
parent 9ca7541d52
commit dd153d3c5c
2 changed files with 149 additions and 76 deletions
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208
opt.cpp
View File

@@ -78,6 +78,12 @@
#endif
#include <llvm/Analysis/DebugInfo.h>
#include <llvm/Support/Dwarf.h>
#ifdef ISPC_IS_LINUX
#include <alloca.h>
#elif defined(ISPC_IS_WINDOWS)
#include <malloc.h>
#define alloca _alloca
#endif // ISPC_IS_WINDOWS
static llvm::Pass *CreateIntrinsicsOptPass();
static llvm::Pass *CreateGatherScatterFlattenPass();
@@ -1520,8 +1526,8 @@ static void lPrintVector(const char *info, llvm::Value *elements[ISPC_MAX_NVEC])
/** Given an LLVM vector in vec, return a 'scalarized' version of the
vector in the provided offsets[] array. For example, if the vector
value passed in is:
vector in the provided scalarizedVector[] array. For example, if the
vector value passed in is:
add <4 x i32> %a_smear, <4 x i32> <4, 8, 12, 16>,
@@ -1542,28 +1548,39 @@ static void lPrintVector(const char *info, llvm::Value *elements[ISPC_MAX_NVEC])
@param vec Vector to be scalarized
@param scalarizedVector Array in which to store the individual vector
elements
@param vectorLength Number of elements in the given vector. (The
passed scalarizedVector array must also be at least
this length as well.)
@returns True if the vector was successfully scalarized and
the values in offsets[] are valid; false otherwise
*/
static bool
lScalarizeVector(llvm::Value *vec, llvm::Value *scalarizedVector[ISPC_MAX_NVEC]) {
lScalarizeVector(llvm::Value *vec, llvm::Value **scalarizedVector,
int vectorLength) {
// First initialize the values of scalarizedVector[] to NULL.
for (int i = 0; i < g->target.vectorWidth; ++i)
for (int i = 0; i < vectorLength; ++i)
scalarizedVector[i] = NULL;
// It may be ok for the vector to be an undef vector; these come up for
// example in shufflevector instructions. As long as elements of the
// undef vector aren't referenced by the shuffle indices, this is fine.
if (llvm::isa<llvm::UndefValue>(vec))
return true;
// ConstantVectors are easy; just pull out the individual constant
// element values
llvm::ConstantVector *cv = llvm::dyn_cast<llvm::ConstantVector>(vec);
if (cv != NULL) {
for (int i = 0; i < g->target.vectorWidth; ++i)
for (int i = 0; i < vectorLength; ++i)
scalarizedVector[i] = cv->getOperand(i);
return true;
}
// It's also easy if it's just a vector of all zeros
llvm::ConstantAggregateZero *caz = llvm::dyn_cast<llvm::ConstantAggregateZero>(vec);
if (caz) {
for (int i = 0; i < g->target.vectorWidth; ++i)
llvm::ConstantAggregateZero *caz =
llvm::dyn_cast<llvm::ConstantAggregateZero>(vec);
if (caz != NULL) {
for (int i = 0; i < vectorLength; ++i)
scalarizedVector[i] = LLVMInt32(0);
return true;
}
@@ -1575,13 +1592,16 @@ lScalarizeVector(llvm::Value *vec, llvm::Value *scalarizedVector[ISPC_MAX_NVEC])
// scalar values we return from here are synthesized with scalar
// versions of the original vector binary operator
llvm::Instruction::BinaryOps opcode = bo->getOpcode();
llvm::Value *v0[ISPC_MAX_NVEC], *v1[ISPC_MAX_NVEC];
llvm::Value **v0 =
(llvm::Value **)alloca(vectorLength * sizeof(llvm::Value *));
llvm::Value **v1 =
(llvm::Value **)alloca(vectorLength * sizeof(llvm::Value *));
if (!lScalarizeVector(bo->getOperand(0), v0) ||
!lScalarizeVector(bo->getOperand(1), v1))
if (!lScalarizeVector(bo->getOperand(0), v0, vectorLength) ||
!lScalarizeVector(bo->getOperand(1), v1, vectorLength))
return false;
for (int i = 0; i < g->target.vectorWidth; ++i) {
for (int i = 0; i < vectorLength; ++i) {
scalarizedVector[i] =
llvm::BinaryOperator::Create(opcode, v0[i], v1[i], "flat_bop", bo);
lCopyMetadata(scalarizedVector[i], bo);
@@ -1606,7 +1626,7 @@ lScalarizeVector(llvm::Value *vec, llvm::Value *scalarizedVector[ISPC_MAX_NVEC])
// vaue in scalarizedVector[] based on the value being inserted.
while (ie != NULL) {
uint64_t iOffset = lGetIntValue(ie->getOperand(2));
assert((int)iOffset < g->target.vectorWidth);
assert((int)iOffset < vectorLength);
assert(scalarizedVector[iOffset] == NULL);
scalarizedVector[iOffset] = ie->getOperand(1);
@@ -1620,15 +1640,17 @@ lScalarizeVector(llvm::Value *vec, llvm::Value *scalarizedVector[ISPC_MAX_NVEC])
}
llvm::CastInst *ci = llvm::dyn_cast<llvm::CastInst>(vec);
if (ci) {
if (ci != NULL) {
// Casts are similar to BinaryOperators in that we attempt to
// scalarize the vector being cast and if successful, we apply
// equivalent scalar cast operators to each of the values in the
// scalarized vector.
llvm::Instruction::CastOps op = ci->getOpcode();
llvm::Value *scalarizedTarget[ISPC_MAX_NVEC];
if (!lScalarizeVector(ci->getOperand(0), scalarizedTarget))
llvm::Value **scalarizedTarget =
(llvm::Value **)alloca(vectorLength * sizeof(llvm::Value *));
if (!lScalarizeVector(ci->getOperand(0), scalarizedTarget,
vectorLength))
return false;
LLVM_TYPE_CONST llvm::Type *destType = ci->getDestTy();
@@ -1637,7 +1659,7 @@ lScalarizeVector(llvm::Value *vec, llvm::Value *scalarizedVector[ISPC_MAX_NVEC])
assert(vectorDestType != NULL);
LLVM_TYPE_CONST llvm::Type *elementType = vectorDestType->getElementType();
for (int i = 0; i < g->target.vectorWidth; ++i) {
for (int i = 0; i < vectorLength; ++i) {
scalarizedVector[i] =
llvm::CastInst::Create(op, scalarizedTarget[i], elementType,
"cast", ci);
@@ -1647,16 +1669,11 @@ lScalarizeVector(llvm::Value *vec, llvm::Value *scalarizedVector[ISPC_MAX_NVEC])
}
llvm::ShuffleVectorInst *svi = llvm::dyn_cast<llvm::ShuffleVectorInst>(vec);
if (svi) {
// Note that the code for shufflevector instructions is untested.
// (We haven't yet had a case where it needs to run). Therefore,
// an assert at the bottom of this routien will hit the first time
// it runs as a reminder that this needs to be tested further.
if (svi != NULL) {
LLVM_TYPE_CONST llvm::VectorType *svInstType =
llvm::dyn_cast<LLVM_TYPE_CONST llvm::VectorType>(svi->getType());
assert(svInstType != NULL);
assert((int)svInstType->getNumElements() == g->target.vectorWidth);
assert((int)svInstType->getNumElements() == vectorLength);
// Scalarize the two vectors being shuffled. First figure out how
// big they are.
@@ -1671,58 +1688,90 @@ lScalarizeVector(llvm::Value *vec, llvm::Value *scalarizedVector[ISPC_MAX_NVEC])
int n0 = vectorType0->getNumElements();
int n1 = vectorType1->getNumElements();
// FIXME: It's actually totally legitimate for these two to have
// different sizes; the final result just needs to have the native
// vector width. To handle this, not only do we need to
// potentially dynamically allocate space for the arrays passed
// into lScalarizeVector, but we need to change the rest of its
// implementation to not key off g->target.vectorWidth everywhere
// to get the sizes of the arrays to iterate over, etc.
assert(n0 == g->target.vectorWidth && n1 == g->target.vectorWidth);
// Go ahead and scalarize the two input vectors now.
// FIXME: it's ok if some or all of the values of these two vectors
// have undef values, so long as we don't try to access undef
// values with the vector indices provided to the instruction.
// Should fix lScalarizeVector so that it doesn't return false in
// this case and just leaves the elements of the arrays with undef
// values as NULL.
llvm::Value *v0[ISPC_MAX_NVEC], *v1[ISPC_MAX_NVEC];
if (!lScalarizeVector(svi->getOperand(0), v0) ||
!lScalarizeVector(svi->getOperand(1), v1))
llvm::Value **v0 = (llvm::Value **)alloca(n0 * sizeof(llvm::Value *));
llvm::Value **v1 = (llvm::Value **)alloca(n1 * sizeof(llvm::Value *));
if (!lScalarizeVector(svi->getOperand(0), v0, n0) ||
!lScalarizeVector(svi->getOperand(1), v1, n1))
return false;
llvm::ConstantVector *shuffleIndicesVector =
llvm::dyn_cast<llvm::ConstantVector>(svi->getOperand(2));
// I think this has to be a ConstantVector. If this ever hits,
// we'll dig into what we got instead and figure out how to handle
// that...
assert(shuffleIndicesVector != NULL);
// Get the integer indices for each element of the returned vector
llvm::SmallVector<llvm::Constant *, ISPC_MAX_NVEC> shuffleIndices;
shuffleIndicesVector->getVectorElements(shuffleIndices);
assert((int)shuffleIndices.size() == g->target.vectorWidth);
// And loop over the indices, setting the i'th element of the
// result vector with the source vector element that corresponds to
// the i'th shuffle index value.
for (unsigned int i = 0; i < shuffleIndices.size(); ++i) {
if (!llvm::isa<llvm::ConstantInt>(shuffleIndices[i]))
// I'm not sure when this case would ever happen, though..
return false;
int offset = (int)lGetIntValue(shuffleIndices[i]);
assert(offset >= 0 && offset < n0+n1);
if (offset < n0)
// Offsets from 0 to n0-1 index into the first vector
scalarizedVector[i] = v0[offset];
else
// And offsets from n0 to (n0+n1-1) index into the second
// vector
scalarizedVector[i] = v1[offset - n0];
llvm::ConstantAggregateZero *caz =
llvm::dyn_cast<llvm::ConstantAggregateZero>(svi->getOperand(2));
if (caz != NULL) {
for (int i = 0; i < vectorLength; ++i)
scalarizedVector[i] = v0[0];
}
else {
llvm::ConstantVector *shuffleIndicesVector =
llvm::dyn_cast<llvm::ConstantVector>(svi->getOperand(2));
// I think this has to be a ConstantVector. If this ever hits,
// we'll dig into what we got instead and figure out how to handle
// that...
assert(shuffleIndicesVector != NULL);
// Get the integer indices for each element of the returned vector
llvm::SmallVector<llvm::Constant *, ISPC_MAX_NVEC> shuffleIndices;
shuffleIndicesVector->getVectorElements(shuffleIndices);
assert((int)shuffleIndices.size() == vectorLength);
// And loop over the indices, setting the i'th element of the
// result vector with the source vector element that corresponds to
// the i'th shuffle index value.
for (unsigned int i = 0; i < shuffleIndices.size(); ++i) {
// I'm not sure when this case would ever happen, though..
assert(llvm::isa<llvm::ConstantInt>(shuffleIndices[i]));
int offset = (int)lGetIntValue(shuffleIndices[i]);
assert(offset >= 0 && offset < n0+n1);
if (offset < n0)
// Offsets from 0 to n0-1 index into the first vector
scalarizedVector[i] = v0[offset];
else
// And offsets from n0 to (n0+n1-1) index into the second
// vector
scalarizedVector[i] = v1[offset - n0];
}
}
return true;
}
llvm::LoadInst *li = llvm::dyn_cast<llvm::LoadInst>(vec);
if (li != NULL) {
llvm::Value *baseAddr = li->getOperand(0);
llvm::Value *baseInt = new llvm::PtrToIntInst(baseAddr, LLVMTypes::Int64Type,
"base2int", li);
lCopyMetadata(baseInt, li);
LLVM_TYPE_CONST llvm::PointerType *ptrType =
llvm::dyn_cast<llvm::PointerType>(baseAddr->getType());
assert(ptrType != NULL);
LLVM_TYPE_CONST llvm::VectorType *vecType =
llvm::dyn_cast<llvm::VectorType>(ptrType->getElementType());
assert(vecType != NULL);
LLVM_TYPE_CONST llvm::Type *elementType = vecType->getElementType();
uint64_t elementSize;
bool sizeKnown = lSizeOfIfKnown(elementType, &elementSize);
assert(sizeKnown == true);
LLVM_TYPE_CONST llvm::Type *eltPtrType = llvm::PointerType::get(elementType, 0);
for (int i = 0; i < vectorLength; ++i) {
llvm::Value *intPtrOffset =
llvm::BinaryOperator::Create(llvm::Instruction::Add, baseInt,
LLVMInt64(i * elementSize), "baseoffset",
li);
lCopyMetadata(intPtrOffset, li);
llvm::Value *scalarLoadPtr =
new llvm::IntToPtrInst(intPtrOffset, eltPtrType, "int2ptr", li);
lCopyMetadata(scalarLoadPtr, li);
llvm::Instruction *scalarLoad =
new llvm::LoadInst(scalarLoadPtr, "loadelt", li);
lCopyMetadata(scalarLoad, li);
scalarizedVector[i] = scalarLoad;
}
FATAL("the above code is untested so far; check now that it's actually running");
return true;
}
@@ -2134,11 +2183,18 @@ GSImprovementsPass::runOnBasicBlock(llvm::BasicBlock &bb) {
if (ce && ce->getOpcode() == llvm::Instruction::BitCast)
base = ce->getOperand(0);
// Try to out the offsets; the i'th element of the offsetElements
// array should be an i32 with the value of the offset for the i'th
// vector lane. This may fail; if so, just give up.
// Try to find out the offsets; the i'th element of the
// offsetElements array should be an i32 with the value of the
// offset for the i'th vector lane. This may fail; if so, just
// give up.
llvm::Value *vecValue = callInst->getArgOperand(1);
LLVM_TYPE_CONST llvm::VectorType *vt =
llvm::dyn_cast<llvm::VectorType>(vecValue->getType());
assert(vt != NULL);
int vecLength = vt->getNumElements();
assert(vecLength == g->target.vectorWidth);
llvm::Value *offsetElements[ISPC_MAX_NVEC];
if (!lScalarizeVector(callInst->getArgOperand(1), offsetElements))
if (!lScalarizeVector(vecValue, offsetElements, vecLength))
continue;
llvm::Value *mask = callInst->getArgOperand((gatherInfo != NULL) ? 2 : 3);

17
tests/shuffle-flatten.ispc Normal file
View File

@@ -0,0 +1,17 @@
export uniform int width() { return programCount; }
export void f_f(uniform float RET[], uniform float aFOO[]) {
int tmp1 = shuffle(programIndex, 0, programIndex);
RET[programIndex] = 10;
if (programIndex < 1) {
uniform int foo = extract(tmp1, 0);
RET[programIndex] = aFOO[foo + programIndex];
}
}
export void result(uniform float RET[]) {
RET[programIndex] = 10;
RET[0] = 1;
}