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Fast path slice contiguous constant #137

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merged 2 commits into from
Oct 8, 2024
Merged

Fast path slice contiguous constant #137

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873842d
Fast path slice contiguous constant
wsmoses Oct 8, 2024
0d3e456
fmt
wsmoses Oct 8, 2024
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52 changes: 48 additions & 4 deletions src/enzyme_ad/jax/Passes/EnzymeHLOOpt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3011,6 +3011,21 @@ struct ConvertSimplify : public OpRewritePattern<mlir::stablehlo::ConvertOp> {
struct SliceSimplify : public OpRewritePattern<mlir::stablehlo::SliceOp> {
using OpRewritePattern<mlir::stablehlo::SliceOp>::OpRewritePattern;

static int64_t getSizeInBytes(Type type) {
if (auto shapedType = dyn_cast<ShapedType>(type))
return shapedType.getNumElements() *
getSizeInBytes(shapedType.getElementType());

if (type.isIntOrFloat())
return std::max(type.getIntOrFloatBitWidth(), (unsigned)8) / 8;

if (auto complexType = dyn_cast<mlir::ComplexType>(type))
return getSizeInBytes(complexType.getElementType()) * 2;

report_fatal_error(
invalidArgument("Unsupported type: %s", debugString(type).c_str()));
}

LogicalResult matchAndRewrite(mlir::stablehlo::SliceOp op,
PatternRewriter &rewriter) const final {
DenseElementsAttr inp;
Expand All @@ -3020,12 +3035,41 @@ struct SliceSimplify : public OpRewritePattern<mlir::stablehlo::SliceOp> {
if (inp.isSplat()) {
out = inp.resizeSplat(op.getType());
} else {
bool contiguous = true;
size_t offset = 0;
auto inshape = op.getOperand().getType().getShape();
size_t total = 1;
for (int i = inshape.size() - 1; i >= 0; i--) {
if (op.getStrides()[i] != 1) {
contiguous = false;
}
auto start = op.getStartIndices()[i];
auto lim = op.getLimitIndices()[i];
if (start != 0 || lim != inshape[i]) {
if (offset != 0) {
contiguous = false;
}
}
offset *= inshape[i];
offset += start;
total *= inshape[i];
}

auto ten = mlir::stablehlo::constantOp(inp);
out = fromTensor(mlir::stablehlo::sliceOp(
ten, stablehlo::Sizes(op.getStartIndices()),
stablehlo::Sizes(op.getStrides()), op.getType()));
}

if (contiguous) {
auto elementType = op.getOperand().getType().getElementType();
const char *elementPtr =
out.getRawData().data() + getSizeInBytes(elementType) * offset;

auto values = ArrayRef((char *)elementPtr, total);
out = DenseIntOrFPElementsAttr::getFromRawBuffer(op.getType(),
floatValues);
} else
out = fromTensor(mlir::stablehlo::sliceOp(
ten, stablehlo::Sizes(op.getStartIndices()),
stablehlo::Sizes(op.getStrides()), op.getType()));
}
rewriter.replaceOpWithNewOp<stablehlo::ConstantOp>(op, op.getType(), out);
return success();
}
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