ArithToAMDGPU.cpp

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//===- ArithToAMDGPU.cpp - Arith to AMDGPU dialect conversion ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include "mlir/Conversion/ArithToAMDGPU/ArithToAMDGPU.h"
 
#include "mlir/Dialect/AMDGPU/IR/AMDGPUDialect.h"
#include "mlir/Dialect/AMDGPU/Utils/Chipset.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Arith/Utils/Utils.h"
#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
#include "mlir/Dialect/LLVMIR/ROCDLDialect.h"
#include "mlir/Dialect/Utils/IndexingUtils.h"
#include "mlir/Dialect/Vector/IR/VectorOps.h"
#include "mlir/Dialect/Vector/Transforms/VectorRewritePatterns.h"
#include "mlir/Dialect/Vector/Utils/VectorUtils.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/IR/TypeUtilities.h"
#include "mlir/Pass/Pass.h"
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
 
namespace mlir {
#define GEN_PASS_DEF_ARITHTOAMDGPUCONVERSIONPASS
#include "mlir/Conversion/Passes.h.inc"
} // namespace mlir
 
using namespace mlir;
using namespace mlir::amdgpu;
 
namespace {
// Define commonly used chipsets versions for convenience.
constexpr Chipset kGfx942 = Chipset(9, 4, 2);
constexpr Chipset kGfx950 = Chipset(9, 5, 0);
 
struct ArithToAMDGPUConversionPass final
    : impl::ArithToAMDGPUConversionPassBase<ArithToAMDGPUConversionPass> {
  using impl::ArithToAMDGPUConversionPassBase<
      ArithToAMDGPUConversionPass>::ArithToAMDGPUConversionPassBase;
 
  void runOnOperation() override;
};
 
struct ExtFOnFloat8RewritePattern final : OpRewritePattern<arith::ExtFOp> {
  using Base::Base;
 
  Chipset chipset;
  ExtFOnFloat8RewritePattern(MLIRContext *ctx, Chipset chipset,
                             PatternBenefit benefit)
      : OpRewritePattern::OpRewritePattern(ctx, benefit), chipset(chipset) {}
 
  LogicalResult matchAndRewrite(arith::ExtFOp op,
                                PatternRewriter &rewriter) const override;
};
 
struct TruncFToFloat8RewritePattern final : OpRewritePattern<arith::TruncFOp> {
  bool saturateFP8 = false;
  TruncFToFloat8RewritePattern(MLIRContext *ctx, bool saturateFP8,
                               Chipset chipset, PatternBenefit benefit)
      : OpRewritePattern::OpRewritePattern(ctx, benefit),
        saturateFP8(saturateFP8), chipset(chipset) {}
  Chipset chipset;
 
  LogicalResult matchAndRewrite(arith::TruncFOp op,
                                PatternRewriter &rewriter) const override;
};
 
struct TruncfToFloat16RewritePattern final
    : public OpRewritePattern<arith::TruncFOp> {
 
  using Base::Base;
 
  LogicalResult matchAndRewrite(arith::TruncFOp op,
                                PatternRewriter &rewriter) const override;
};
 
struct ScalingExtFRewritePattern final
    : OpRewritePattern<arith::ScalingExtFOp> {
  using Base::Base;
 
  LogicalResult matchAndRewrite(arith::ScalingExtFOp op,
                                PatternRewriter &rewriter) const override;
};
 
struct ScalingTruncFRewritePattern final
    : OpRewritePattern<arith::ScalingTruncFOp> {
  using Base::Base;
 
  LogicalResult matchAndRewrite(arith::ScalingTruncFOp op,
                                PatternRewriter &rewriter) const override;
};
 
} // end namespace
 
static bool isSupportedF8(Type elementType, Chipset chipset) {
  if (chipset == kGfx942)
    return isa<Float8E4M3FNUZType, Float8E5M2FNUZType>(elementType);
  if (hasOcpFp8(chipset))
    return isa<Float8E4M3FNType, Float8E5M2Type>(elementType);
  return false;
}
 
static Value castF32To(Type desType, Value f32, Location loc,
                       PatternRewriter &rewriter) {
  Type elementType = getElementTypeOrSelf(desType);
  if (elementType.isF32())
    return f32;
  if (elementType.getIntOrFloatBitWidth() < 32)
    return arith::TruncFOp::create(rewriter, loc, desType, f32);
  if (elementType.getIntOrFloatBitWidth() > 32)
    return arith::ExtFOp::create(rewriter, loc, desType, f32);
  llvm_unreachable("The only 32-bit float type is f32");
}
 
LogicalResult
ExtFOnFloat8RewritePattern::matchAndRewrite(arith::ExtFOp op,
                                            PatternRewriter &rewriter) const {
  Type inType = op.getIn().getType();
  auto inVecType = dyn_cast<VectorType>(inType);
  if (inVecType) {
    if (inVecType.isScalable())
      return failure();
    inType = inVecType.getElementType();
  }
  if (!isSupportedF8(inType, chipset))
    return failure();
 
  Location loc = op.getLoc();
  Value in = op.getIn();
  Type outElemType = getElementTypeOrSelf(op.getOut().getType());
  VectorType extResType = VectorType::get(2, rewriter.getF32Type());
  if (!inVecType) {
    Value asFloat = amdgpu::ExtPackedFp8Op::create(
        rewriter, loc, rewriter.getF32Type(), in, 0);
    Value result = castF32To(outElemType, asFloat, loc, rewriter);
    rewriter.replaceOp(op, result);
    return success();
  }
  int64_t numElements = inVecType.getNumElements();
 
  Value zero = arith::ConstantOp::create(
      rewriter, loc, outElemType, rewriter.getFloatAttr(outElemType, 0.0));
  VectorType outType = cast<VectorType>(op.getOut().getType());
 
  if (inVecType.getShape().empty()) {
    Value zerodSplat =
        rewriter.createOrFold<vector::BroadcastOp>(loc, outType, zero);
    Value scalarIn =
        vector::ExtractOp::create(rewriter, loc, in, ArrayRef<int64_t>{});
    Value scalarExt =
        arith::ExtFOp::create(rewriter, loc, outElemType, scalarIn);
    Value result = vector::InsertOp::create(rewriter, loc, scalarExt,
                                            zerodSplat, ArrayRef<int64_t>{});
    rewriter.replaceOp(op, result);
    return success();
  }
 
  VectorType flatTy = VectorType::get(SmallVector<int64_t>{numElements},
                                      outType.getElementType());
  Value result = rewriter.createOrFold<vector::BroadcastOp>(loc, flatTy, zero);
 
  if (inVecType.getRank() > 1) {
    inVecType = VectorType::get(SmallVector<int64_t>{numElements},
                                inVecType.getElementType());
    in = vector::ShapeCastOp::create(rewriter, loc, inVecType, in);
  }
 
  for (int64_t i = 0; i < numElements; i += 4) {
    int64_t elemsThisOp = std::min(numElements, i + 4) - i;
    Value inSlice = vector::ExtractStridedSliceOp::create(rewriter, loc, in, i,
                                                          elemsThisOp, 1);
    for (int64_t j = 0; j < elemsThisOp; j += 2) {
      if (i + j + 1 < numElements) { // Convert two 8-bit elements
        Value asFloats = amdgpu::ExtPackedFp8Op::create(
            rewriter, loc, extResType, inSlice, j / 2);
        Type desType = VectorType::get(2, outElemType);
        Value asType = castF32To(desType, asFloats, loc, rewriter);
        result = vector::InsertStridedSliceOp::create(rewriter, loc, asType,
                                                      result, i + j, 1);
      } else { // Convert a 8-bit element
        Value asFloat = amdgpu::ExtPackedFp8Op::create(
            rewriter, loc, rewriter.getF32Type(), inSlice, j / 2 * 2);
        Value asType = castF32To(outElemType, asFloat, loc, rewriter);
        result = vector::InsertOp::create(rewriter, loc, asType, result, i + j);
      }
    }
  }
 
  if (inVecType.getRank() != outType.getRank()) {
    result = vector::ShapeCastOp::create(rewriter, loc, outType, result);
  }
 
  rewriter.replaceOp(op, result);
  return success();
}
 
static Value castToF32(Value value, Location loc, PatternRewriter &rewriter) {
  Type type = value.getType();
  if (type.isF32())
    return value;
  if (type.getIntOrFloatBitWidth() < 32)
    return arith::ExtFOp::create(rewriter, loc, rewriter.getF32Type(), value);
  if (type.getIntOrFloatBitWidth() > 32)
    return arith::TruncFOp::create(rewriter, loc, rewriter.getF32Type(), value);
  llvm_unreachable("The only 32-bit float type is f32");
}
 
// If `in` is a finite value, clamp it between the maximum and minimum values
// of `outElemType` so that subsequent conversion instructions don't
// overflow those out-of-range values to NaN. These semantics are commonly
// used in machine-learning contexts where failure to clamp would lead to
// excessive NaN production.
static Value clampInput(PatternRewriter &rewriter, Location loc,
                        Type outElemType, Value source) {
  Type sourceType = source.getType();
  const llvm::fltSemantics &sourceSem =
      cast<FloatType>(getElementTypeOrSelf(sourceType)).getFloatSemantics();
  const llvm::fltSemantics &targetSem =
      cast<FloatType>(outElemType).getFloatSemantics();
 
  APFloat min = APFloat::getLargest(targetSem, /*Negative=*/true);
  APFloat max = APFloat::getLargest(targetSem, /*Negative=*/false);
  bool ignoredLosesInfo = false;
  // We can ignore conversion failures here because this conversion promotes
  // from a smaller type to a larger one - ex. there can be no loss of precision
  // when casting fp8 to f16.
  (void)min.convert(sourceSem, APFloat::rmNearestTiesToEven, &ignoredLosesInfo);
  (void)max.convert(sourceSem, APFloat::rmNearestTiesToEven, &ignoredLosesInfo);
 
  Value minCst = createScalarOrSplatConstant(rewriter, loc, sourceType, min);
  Value maxCst = createScalarOrSplatConstant(rewriter, loc, sourceType, max);
 
  Value inf = createScalarOrSplatConstant(
      rewriter, loc, sourceType,
      APFloat::getInf(sourceSem, /*Negative=*/false));
  Value negInf = createScalarOrSplatConstant(
      rewriter, loc, sourceType, APFloat::getInf(sourceSem, /*Negative=*/true));
  Value isInf = rewriter.createOrFold<arith::CmpFOp>(
      loc, arith::CmpFPredicate::OEQ, source, inf);
  Value isNegInf = rewriter.createOrFold<arith::CmpFOp>(
      loc, arith::CmpFPredicate::OEQ, source, negInf);
  Value isNan = rewriter.createOrFold<arith::CmpFOp>(
      loc, arith::CmpFPredicate::UNO, source, source);
  Value isNonFinite = arith::OrIOp::create(
      rewriter, loc, arith::OrIOp::create(rewriter, loc, isInf, isNegInf),
      isNan);
 
  Value clampedBelow = arith::MaximumFOp::create(rewriter, loc, source, minCst);
  Value clamped =
      arith::MinimumFOp::create(rewriter, loc, clampedBelow, maxCst);
  Value res =
      arith::SelectOp::create(rewriter, loc, isNonFinite, source, clamped);
  return res;
}
 
LogicalResult
TruncFToFloat8RewritePattern::matchAndRewrite(arith::TruncFOp op,
                                              PatternRewriter &rewriter) const {
  // Only supporting default rounding mode as of now.
  if (op.getRoundingmodeAttr())
    return failure();
  Type outType = op.getOut().getType();
  auto outVecType = dyn_cast<VectorType>(outType);
  if (outVecType) {
    if (outVecType.isScalable())
      return failure();
    outType = outVecType.getElementType();
  }
  auto inType = dyn_cast<FloatType>(getElementTypeOrSelf(op.getIn().getType()));
  if (inType && inType.getWidth() <= 8 && saturateFP8)
    // Conversion between 8-bit floats is not supported with truncation enabled.
    return failure();
 
  if (!isSupportedF8(outType, chipset))
    return failure();
 
  Location loc = op.getLoc();
  Value in = op.getIn();
  Type outElemType = getElementTypeOrSelf(op.getOut().getType());
  if (saturateFP8)
    in = clampInput(rewriter, loc, outElemType, in);
  auto inVectorTy = dyn_cast<VectorType>(in.getType());
  VectorType truncResType = VectorType::get(4, outElemType);
  if (!inVectorTy) {
    Value asFloat = castToF32(in, loc, rewriter);
    Value asF8s = amdgpu::PackedTrunc2xFp8Op::create(
        rewriter, loc, truncResType, asFloat, /*sourceB=*/nullptr, 0,
        /*existing=*/nullptr);
    Value result = vector::ExtractOp::create(rewriter, loc, asF8s, 0);
    rewriter.replaceOp(op, result);
    return success();
  }
 
  int64_t numElements = outVecType.getNumElements();
  Value zero = arith::ConstantOp::create(
      rewriter, loc, outElemType, rewriter.getFloatAttr(outElemType, 0.0));
  if (outVecType.getShape().empty()) {
    Value scalarIn =
        vector::ExtractOp::create(rewriter, loc, in, ArrayRef<int64_t>{});
    // Recurse to send the 0-D vector case to the 1-D vector case
    Value scalarTrunc =
        arith::TruncFOp::create(rewriter, loc, outElemType, scalarIn);
    Value result = vector::InsertOp::create(rewriter, loc, scalarTrunc, zero,
                                            ArrayRef<int64_t>{});
    rewriter.replaceOp(op, result);
    return success();
  }
 
  VectorType flatTy = VectorType::get(SmallVector<int64_t>{numElements},
                                      outVecType.getElementType());
  Value result = rewriter.createOrFold<vector::BroadcastOp>(loc, flatTy, zero);
 
  if (inVectorTy.getRank() > 1) {
    inVectorTy = VectorType::get(SmallVector<int64_t>{numElements},
                                 inVectorTy.getElementType());
    in = vector::ShapeCastOp::create(rewriter, loc, inVectorTy, in);
  }
 
  for (int64_t i = 0; i < numElements; i += 4) {
    int64_t elemsThisOp = std::min(numElements, i + 4) - i;
    Value thisResult = nullptr;
    for (int64_t j = 0; j < elemsThisOp; j += 2) {
      Value elemA = vector::ExtractOp::create(rewriter, loc, in, i + j);
      Value asFloatA = castToF32(elemA, loc, rewriter);
      Value asFloatB = nullptr;
      if (j + 1 < elemsThisOp) {
        Value elemB = vector::ExtractOp::create(rewriter, loc, in, i + j + 1);
        asFloatB = castToF32(elemB, loc, rewriter);
      }
      thisResult = amdgpu::PackedTrunc2xFp8Op::create(
          rewriter, loc, truncResType, asFloatA, asFloatB, j / 2, thisResult);
    }
    if (elemsThisOp < 4)
      thisResult = vector::ExtractStridedSliceOp::create(
          rewriter, loc, thisResult, 0, elemsThisOp, 1);
    result = vector::InsertStridedSliceOp::create(rewriter, loc, thisResult,
                                                  result, i, 1);
  }
 
  if (inVectorTy.getRank() != outVecType.getRank()) {
    result = vector::ShapeCastOp::create(rewriter, loc, outVecType, result);
  }
 
  rewriter.replaceOp(op, result);
  return success();
}
 
LogicalResult TruncfToFloat16RewritePattern::matchAndRewrite(
    arith::TruncFOp op, PatternRewriter &rewriter) const {
  Type outType = op.getOut().getType();
  Type inputType = getElementTypeOrSelf(op.getIn());
  auto outVecType = dyn_cast<VectorType>(outType);
  if (outVecType) {
    if (outVecType.isScalable())
      return failure();
    outType = outVecType.getElementType();
  }
  if (!(outType.isF16() && inputType.isF32()))
    return failure();
 
  Location loc = op.getLoc();
  Value in = op.getIn();
  Type outElemType = getElementTypeOrSelf(op.getOut().getType());
  VectorType truncResType = VectorType::get(2, outElemType);
  auto inVectorTy = dyn_cast<VectorType>(in.getType());
 
  // Handle the case where input type is not a vector type
  if (!inVectorTy) {
    auto sourceB = LLVM::PoisonOp::create(rewriter, loc, rewriter.getF32Type());
    Value asF16s =
        ROCDL::CvtPkRtz::create(rewriter, loc, truncResType, in, sourceB);
    Value result = vector::ExtractOp::create(rewriter, loc, asF16s, 0);
    rewriter.replaceOp(op, result);
    return success();
  }
  int64_t numElements = outVecType.getNumElements();
  Value zero = rewriter.createOrFold<arith::ConstantOp>(
      loc, outElemType, rewriter.getFloatAttr(outElemType, 0.0));
  Value result =
      rewriter.createOrFold<vector::BroadcastOp>(loc, outVecType, zero);
 
  if (inVectorTy.getRank() > 1) {
    inVectorTy = VectorType::get(SmallVector<int64_t>{numElements},
                                 inVectorTy.getElementType());
    in = vector::ShapeCastOp::create(rewriter, loc, inVectorTy, in);
  }
 
  // Handle the vector case. We also handle the (uncommon) case where the vector
  // length is odd
  for (int64_t i = 0; i < numElements; i += 2) {
    int64_t elemsThisOp = std::min(numElements, i + 2) - i;
    Value thisResult = nullptr;
    Value elemA = vector::ExtractOp::create(rewriter, loc, in, i);
    Value elemB = LLVM::PoisonOp::create(rewriter, loc, rewriter.getF32Type());
 
    if (elemsThisOp == 2) {
      elemB = vector::ExtractOp::create(rewriter, loc, in, i + 1);
    }
 
    thisResult =
        ROCDL::CvtPkRtz::create(rewriter, loc, truncResType, elemA, elemB);
    // Place back the truncated result into the possibly larger vector. If we
    // are operating on a size 2 vector, these operations should be folded away
    thisResult = vector::ExtractStridedSliceOp::create(
        rewriter, loc, thisResult, 0, elemsThisOp, 1);
    result = vector::InsertStridedSliceOp::create(rewriter, loc, thisResult,
                                                  result, i, 1);
  }
 
  if (inVectorTy.getRank() != outVecType.getRank()) {
    result = vector::ShapeCastOp::create(rewriter, loc, outVecType, result);
  }
 
  rewriter.replaceOp(op, result);
  return success();
}
 
/// Get the broadcasted / splatted value for a chain of ops.
static Value getOriginalVectorValue(Value value) {
  Value current = value;
  while (Operation *definingOp = current.getDefiningOp()) {
    bool skipOp = llvm::TypeSwitch<Operation *, bool>(definingOp)
                      .Case([&current](vector::ShapeCastOp op) {
                        current = op.getSource();
                        return true;
                      })
                      .Case([&current](vector::BroadcastOp op) {
                        current = op.getSource();
                        return false;
                      })
                      .Default(false);
 
    if (!skipOp) {
      break;
    }
  }
  return current;
}
 
LogicalResult
ScalingExtFRewritePattern::matchAndRewrite(arith::ScalingExtFOp op,
                                           PatternRewriter &rewriter) const {
  Location loc = op.getLoc();
  constexpr int64_t opOutWidth = 2;
 
  Value in = op.getIn();
  Value scale = op.getScale();
  Value out = op.getOut();
 
  Type f32 = rewriter.getF32Type();
  Type inType = getElementTypeOrSelf(in);
  Type scaleType = getElementTypeOrSelf(scale);
  Type outType = getElementTypeOrSelf(out);
 
  int64_t opInWidth = 32 / inType.getIntOrFloatBitWidth();
 
  VectorType outVecType = dyn_cast<VectorType>(out.getType());
  VectorType scaleVecType = dyn_cast<VectorType>(scale.getType());
 
  if (outVecType && outVecType.isScalable())
    return failure();
 
  if (isa<RankedTensorType>(out.getType()) ||
      isa<RankedTensorType>(in.getType()) ||
      isa<RankedTensorType>(scale.getType()))
    return failure();
 
  Type scaleF32Type =
      scaleVecType ? VectorType::get(scaleVecType.getShape(), f32) : f32;
  if (scaleType.getIntOrFloatBitWidth() < 32)
    scale = arith::ExtFOp::create(rewriter, loc, scaleF32Type, scale);
  else if (scaleType.getIntOrFloatBitWidth() > 32)
    scale = arith::TruncFOp::create(rewriter, loc, scaleF32Type, scale);
 
  VectorType extScaleResultType = VectorType::get(opOutWidth, outType);
 
  if (!outVecType) {
    Value inCast = vector::BroadcastOp::create(rewriter, loc,
                                               VectorType::get(1, inType), in);
    // TODO: replace this with non-packed ScaledExtOp
    Value scaleExt = amdgpu::ScaledExtPackedOp::create(
        rewriter, loc, extScaleResultType, inCast, scale, 0);
    scaleExt = rewriter.replaceOpWithNewOp<vector::ExtractOp>(op, scaleExt, 0);
    return success();
  }
 
  VectorType inVecType = cast<VectorType>(in.getType());
  Value origScale = getOriginalVectorValue(op.getScale());
  VectorType origScaleVecType = dyn_cast<VectorType>(origScale.getType());
 
  ArrayRef<int64_t> inShape = inVecType.getShape();
  SmallVector<int64_t> originalScaleShape;
  if (origScaleVecType)
    llvm::append_range(originalScaleShape, origScaleVecType.getShape());
 
  originalScaleShape.insert(originalScaleShape.end(),
                            inShape.size() - originalScaleShape.size(), 1);
 
  auto maybeRatio = computeShapeRatio(inShape, originalScaleShape);
  assert(maybeRatio &&
         "failed to derive block size from broadcast or splat operation");
 
  SmallVector<int64_t> ratio =
      maybeRatio.value_or(SmallVector<int64_t>(inShape.size(), 1));
 
  int64_t blockSize = computeProduct(ratio);
 
  Value zero = arith::ConstantOp::create(rewriter, loc, outType,
                                         rewriter.getFloatAttr(outType, 0.0));
  Value result =
      rewriter.createOrFold<vector::BroadcastOp>(loc, outVecType, zero);
 
  for (SmallVector<int64_t> offsets : StaticTileOffsetRange(inShape, ratio)) {
    SmallVector<int64_t> strides(offsets.size(), 1);
    Value block = vector::ExtractStridedSliceOp::create(
        rewriter, loc, in, offsets, ratio, strides);
    VectorType block1DType = VectorType::get(blockSize, inType);
    Value block1D =
        vector::ShapeCastOp::create(rewriter, loc, block1DType, block);
    Value uniformScale =
        vector::ExtractOp::create(rewriter, loc, scale, offsets);
 
    VectorType blockResultType = VectorType::get(blockSize, outType);
    Value blockResult =
        rewriter.createOrFold<vector::BroadcastOp>(loc, blockResultType, zero);
 
    for (int64_t i = 0, inSliceWidth = std::min(opInWidth, blockSize - i);
         i < blockSize;
         i += inSliceWidth, inSliceWidth = std::min(opInWidth, blockSize - i)) {
      Value inSlice = vector::ExtractStridedSliceOp::create(
          rewriter, loc, block1D, i, inSliceWidth, 1);
      for (int64_t j = 0,
                   outSliceWidth = std::min(opOutWidth, inSliceWidth - j);
           j < inSliceWidth; j += outSliceWidth,
                   outSliceWidth = std::min(opOutWidth, inSliceWidth - j)) {
        // TODO: replace this with non-packed ScaledExtOp for sliceWidth == 1
        Value scaleExt = amdgpu::ScaledExtPackedOp::create(
            rewriter, loc, extScaleResultType, inSlice, uniformScale,
            j / opOutWidth);
        if (outSliceWidth < opOutWidth) {
          scaleExt = vector::ExtractStridedSliceOp::create(
              rewriter, loc, scaleExt, 0, outSliceWidth, 1);
        }
        blockResult = vector::InsertStridedSliceOp::create(
            rewriter, loc, scaleExt, blockResult, i + j, 1);
      }
    }
 
    VectorType resultType = VectorType::get(ratio, outType);
    Value cast =
        vector::ShapeCastOp::create(rewriter, loc, resultType, blockResult);
    result = vector::InsertStridedSliceOp::create(rewriter, loc, cast, result,
                                                  offsets, strides);
  }
 
  rewriter.replaceOp(op, result);
 
  return success();
}
 
LogicalResult
ScalingTruncFRewritePattern::matchAndRewrite(arith::ScalingTruncFOp op,
                                             PatternRewriter &rewriter) const {
  Location loc = op.getLoc();
  constexpr int64_t opInWidth = 2;
 
  Value in = op.getIn();
  Value scale = op.getScale();
  Value out = op.getOut();
 
  Type f32 = rewriter.getF32Type();
  Type inType = getElementTypeOrSelf(in);
  Type scaleType = getElementTypeOrSelf(scale);
  Type outType = getElementTypeOrSelf(out);
 
  VectorType outVecType = dyn_cast<VectorType>(out.getType());
  VectorType scaleVecType = dyn_cast<VectorType>(scale.getType());
  if (outVecType && outVecType.isScalable())
    return failure();
 
  if (isa<RankedTensorType>(out.getType()) ||
      isa<RankedTensorType>(in.getType()) ||
      isa<RankedTensorType>(scale.getType()))
    return failure();
 
  Type scaleF32Type =
      scaleVecType ? VectorType::get(scaleVecType.getShape(), f32) : f32;
  if (scaleType.getIntOrFloatBitWidth() < 32)
    scale = arith::ExtFOp::create(rewriter, loc, scaleF32Type, scale);
  else if (scaleType.getIntOrFloatBitWidth() > 32)
    scale = arith::TruncFOp::create(rewriter, loc, scaleF32Type, scale);
 
  Value zero = arith::ConstantOp::create(rewriter, loc, outType,
                                         rewriter.getFloatAttr(outType, 0.0));
  int64_t opOutWidth = 32 / outType.getIntOrFloatBitWidth();
  VectorType truncScaleResultType = VectorType::get(opOutWidth, outType);
 
  if (!outVecType) {
    Type inVecType = VectorType::get(1, inType);
    Value inCast = vector::BroadcastOp::create(rewriter, loc, inVecType, in);
    // TODO: replace this with non-packed ScaledTruncOp
    Value scaleTrunc = amdgpu::PackedScaledTruncOp::create(
        rewriter, loc, truncScaleResultType, inCast, scale, 0,
        /*existing=*/nullptr);
    scaleTrunc =
        rewriter.replaceOpWithNewOp<vector::ExtractOp>(op, scaleTrunc, 0);
    return success();
  }
 
  VectorType inVecType = cast<VectorType>(in.getType());
  Value origScale = getOriginalVectorValue(op.getScale());
  VectorType origScaleVecType = dyn_cast<VectorType>(origScale.getType());
 
  ArrayRef<int64_t> inShape = inVecType.getShape();
  SmallVector<int64_t> scaleShape;
  if (origScaleVecType)
    llvm::append_range(scaleShape, origScaleVecType.getShape());
 
  scaleShape.insert(scaleShape.end(), inShape.size() - scaleShape.size(), 1);
 
  auto maybeRatio = computeShapeRatio(inShape, scaleShape);
  assert(maybeRatio &&
         "failed to derive block size from broadcast or splat operation");
 
  SmallVector<int64_t> ratio =
      maybeRatio.value_or(SmallVector<int64_t>(inShape.size(), 1));
 
  int64_t blockSize = computeProduct(ratio);
 
  Value result =
      rewriter.createOrFold<vector::BroadcastOp>(loc, outVecType, zero);
 
  for (SmallVector<int64_t> offsets : StaticTileOffsetRange(inShape, ratio)) {
    SmallVector<int64_t> strides(offsets.size(), 1);
    Value block = vector::ExtractStridedSliceOp::create(
        rewriter, loc, in, offsets, ratio, strides);
    VectorType block1DType = VectorType::get(blockSize, inType);
    Value block1D =
        vector::ShapeCastOp::create(rewriter, loc, block1DType, block);
    Value uniformScale =
        vector::ExtractOp::create(rewriter, loc, scale, offsets);
 
    VectorType blockResultType = VectorType::get(blockSize, outType);
    Value blockResult =
        rewriter.createOrFold<vector::BroadcastOp>(loc, blockResultType, zero);
 
    for (int64_t i = 0, outSliceWidth = std::min(opOutWidth, blockSize - i);
         i < blockSize; i += outSliceWidth,
                 outSliceWidth = std::min(opOutWidth, blockSize - i)) {
      Value scaleTrunc;
      // Case where <= 2 elements are being truncated.
      if (outSliceWidth <= opInWidth) {
        Value slice = vector::ExtractStridedSliceOp::create(
            rewriter, loc, block1D, i, outSliceWidth, 1);
        // TODO: replace this with non-packed ScaledTruncOp for sliceWidth == 1
        scaleTrunc = amdgpu::PackedScaledTruncOp::create(
            rewriter, loc, truncScaleResultType, slice, uniformScale, 0,
            /*existing=*/nullptr);
      } else {
        scaleTrunc = vector::BroadcastOp::create(rewriter, loc,
                                                 truncScaleResultType, zero);
        for (int64_t j = 0,
                     inSliceWidth = std::min(opInWidth, outSliceWidth - j);
             j < outSliceWidth; j += opInWidth,
                     inSliceWidth = std::min(opInWidth, outSliceWidth - j)) {
          Value slice = vector::ExtractStridedSliceOp::create(
              rewriter, loc, block1D, i + j, inSliceWidth, 1);
          scaleTrunc = amdgpu::PackedScaledTruncOp::create(
              rewriter, loc, truncScaleResultType, slice, uniformScale,
              j / opInWidth, scaleTrunc);
        }
      }
      if (outSliceWidth != opOutWidth) {
        scaleTrunc = vector::ExtractStridedSliceOp::create(
            rewriter, loc, scaleTrunc, 0, outSliceWidth, 1);
      }
      blockResult = vector::InsertStridedSliceOp::create(
          rewriter, loc, scaleTrunc, blockResult, i, 1);
    }
 
    VectorType resultType = VectorType::get(ratio, outType);
    Value cast =
        vector::ShapeCastOp::create(rewriter, loc, resultType, blockResult);
    result = vector::InsertStridedSliceOp::create(rewriter, loc, cast, result,
                                                  offsets, strides);
  }
 
  rewriter.replaceOp(op, result);
 
  return success();
}
 
void mlir::arith::populateArithToAMDGPUConversionPatterns(
    RewritePatternSet &patterns, bool convertFP8Arithmetic,
    bool saturateFP8Truncf, bool allowPackedF16Rtz, bool supportsScaledExtTrunc,
    Chipset chipset, PatternBenefit benefit) {
 
  if (convertFP8Arithmetic) {
    patterns.add<ExtFOnFloat8RewritePattern>(patterns.getContext(), chipset,
                                             benefit);
    patterns.add<TruncFToFloat8RewritePattern>(
        patterns.getContext(), saturateFP8Truncf, chipset, benefit);
  }
  if (allowPackedF16Rtz)
    patterns.add<TruncfToFloat16RewritePattern>(patterns.getContext(), benefit);
 
  if (supportsScaledExtTrunc) {
    patterns.add<ScalingExtFRewritePattern>(patterns.getContext(), benefit);
    patterns.add<ScalingTruncFRewritePattern>(patterns.getContext(), benefit);
  }
}
 
void ArithToAMDGPUConversionPass::runOnOperation() {
  Operation *op = getOperation();
  MLIRContext *ctx = &getContext();
  RewritePatternSet patterns(op->getContext());
  FailureOr<amdgpu::Chipset> maybeChipset = amdgpu::Chipset::parse(chipset);
  if (failed(maybeChipset)) {
    emitError(UnknownLoc::get(ctx), "Invalid chipset name: " + chipset);
    return signalPassFailure();
  }
 
  bool convertFP8Arithmetic =
      *maybeChipset == kGfx942 || hasOcpFp8(*maybeChipset);
  bool supportsScaledExtTrunc = *maybeChipset == kGfx950;
  arith::populateArithToAMDGPUConversionPatterns(
      patterns, convertFP8Arithmetic, saturateFP8Truncf, allowPackedF16Rtz,
      supportsScaledExtTrunc, *maybeChipset);
  if (failed(applyPatternsGreedily(op, std::move(patterns))))
    return signalPassFailure();
}