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Generalize code to extract scales by 2/4/8 from addressing calculations.

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Now, if we have a scale by 16, say, we extract out the scalar scale
of 8 and leave an explicit scale by 2.
This commit is contained in:
Matt Pharr
2012-02-10 12:35:44 -08:00
parent 0c25bc063c
commit f20a2d2ee9
1 changed files with 42 additions and 14 deletions
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56
opt.cpp
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@@ -1389,10 +1389,10 @@ lExtractConstantOffset(llvm::Value *vec, llvm::Value **constOffset,
/* Returns true if the given value is a constant vector of integers with
the value 2, 4, 8 in all of the elements. (Returns the splatted value
in *splat, if so). */
the same value in all of the elements. (Returns the splatted value in
*splat, if so). */
static bool
lIs248Splat(llvm::Value *v, int *splat) {
lIsIntegerSplat(llvm::Value *v, int *splat) {
#ifdef LLVM_3_1svn
llvm::ConstantDataVector *cvec =
llvm::dyn_cast<llvm::ConstantDataVector>(v);
@@ -1412,14 +1412,46 @@ lIs248Splat(llvm::Value *v, int *splat) {
return false;
int64_t splatVal = ci->getSExtValue();
if (splatVal != 2 && splatVal != 4 && splatVal != 8)
return false;
*splat = (int)splatVal;
return true;
}
static llvm::Value *
lExtract248Scale(llvm::Value *splatOperand, int splatValue,
llvm::Value *otherOperand, llvm::Value **result) {
if (splatValue == 2 || splatValue == 4 || splatValue == 8) {
*result = otherOperand;
return LLVMInt32(splatValue);
}
// Even if we don't have a common scale by exactly 2, 4, or 8, we'll
// see if we can pull out that much of the scale anyway; this may in
// turn allow other optimizations later.
for (int scale = 8; scale >= 2; scale /= 2) {
llvm::Instruction *insertBefore =
llvm::dyn_cast<llvm::Instruction>(*result);
Assert(insertBefore != NULL);
if ((splatValue % scale) == 0) {
// *result = otherOperand + splatOperand / splatValue;
llvm::Value *splatScaleVec =
(splatOperand->getType() == LLVMTypes::Int32VectorType) ?
LLVMInt32Vector(scale) : LLVMInt64Vector(scale);
llvm::Value *splatDiv =
llvm::BinaryOperator::Create(llvm::Instruction::SDiv,
splatOperand, splatScaleVec,
"div", insertBefore);
*result =
llvm::BinaryOperator::Create(llvm::Instruction::Add,
splatDiv, otherOperand,
"add", insertBefore);
return LLVMInt32(scale);
}
}
return LLVMInt32(1);
}
/** Given a vector of integer offsets to a base pointer being used for a
gather or a scatter, see if its root operation is a multiply by a
vector of some value by all 2s/4s/8s. If not, return NULL.
@@ -1482,14 +1514,10 @@ lExtractOffsetVector248Scale(llvm::Value **vec) {
else if (bop->getOpcode() == llvm::Instruction::Mul) {
// Check each operand for being one of the scale factors we care about.
int splat;
if (lIs248Splat(op0, &splat)) {
*vec = op1;
return LLVMInt32(splat);
}
else if (lIs248Splat(op1, &splat)) {
*vec = op0;
return LLVMInt32(splat);
}
if (lIsIntegerSplat(op0, &splat))
return lExtract248Scale(op0, splat, op1, vec);
else if (lIsIntegerSplat(op1, &splat))
return lExtract248Scale(op1, splat, op0, vec);
else
return LLVMInt32(1);
}