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Revert "[mlir][arith] Add expansion pattern for ext/trunc of bf16"
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This reverts commit 5bff523. The
bf16->f32 conversion is incorrect. This can't be on by default, if you
want this behavior make it a separate pass.
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@d0k
d0k committed Apr 4, 2023
1 parent e5cc3f2 commit 3bde144
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Showing 3 changed files with 8 additions and 163 deletions.
3 changes: 0 additions & 3 deletions mlir/include/mlir/Dialect/Arith/Transforms/Passes.h
View file
Expand Up @@ -38,9 +38,6 @@ void populateArithWideIntEmulationPatterns(
/// Add patterns to expand Arith ceil/floor division ops.
void populateCeilFloorDivExpandOpsPatterns(RewritePatternSet &patterns);

/// Add patterns to expand Arith bf16 patterns to lower level bitcasts/shifts.
void populateExpandBFloat16Patterns(RewritePatternSet &patterns);

/// Add patterns to expand Arith ops.
void populateArithExpandOpsPatterns(RewritePatternSet &patterns);

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104 changes: 8 additions & 96 deletions mlir/lib/Dialect/Arith/Transforms/ExpandOps.cpp
View file
Expand Up @@ -10,7 +10,6 @@

#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Vector/IR/VectorOps.h"
#include "mlir/IR/ImplicitLocOpBuilder.h"
#include "mlir/IR/TypeUtilities.h"
#include "mlir/Transforms/DialectConversion.h"

Expand All @@ -26,13 +25,15 @@ using namespace mlir;
/// Create an integer or index constant.
static Value createConst(Location loc, Type type, int value,
PatternRewriter &rewriter) {
auto attr = rewriter.getIntegerAttr(getElementTypeOrSelf(type), value);
if (auto shapedTy = dyn_cast<ShapedType>(type)) {

auto elTy = getElementTypeOrSelf(type);
auto constantAttr = rewriter.getIntegerAttr(elTy, value);

if (auto vecTy = llvm::dyn_cast<ShapedType>(type))
return rewriter.create<arith::ConstantOp>(
loc, DenseElementsAttr::get(shapedTy, attr));
}
loc, vecTy, DenseElementsAttr::get(vecTy, constantAttr));

return rewriter.create<arith::ConstantOp>(loc, attr);
return rewriter.create<arith::ConstantOp>(loc, constantAttr);
}

namespace {
Expand Down Expand Up @@ -186,73 +187,6 @@ struct MaxMinFOpConverter : public OpRewritePattern<OpTy> {
}
};

struct BFloat16ExtFOpConverter : public OpRewritePattern<arith::ExtFOp> {
using OpRewritePattern::OpRewritePattern;
LogicalResult matchAndRewrite(arith::ExtFOp op,
PatternRewriter &rewriter) const final {
ImplicitLocOpBuilder b(op.getLoc(), rewriter);
auto operand = op.getOperand();
Type operandTy = operand.getType();
Type resultTy = op.getType();
Type operandETy = getElementTypeOrSelf(operandTy);
Type resultETy = getElementTypeOrSelf(resultTy);

if (!operandETy.isBF16() || !resultETy.isF32()) {
return rewriter.notifyMatchFailure(op, "not a ext of bf16 to f32.");
}

Type i16Ty = b.getI16Type();
Type i32Ty = b.getI32Type();
if (auto shapedTy = dyn_cast<ShapedType>(operandTy)) {
i16Ty = shapedTy.clone(i16Ty);
i32Ty = shapedTy.clone(i32Ty);
}

Value bitcast = b.create<arith::BitcastOp>(i16Ty, operand);
Value exti = b.create<arith::ExtUIOp>(i32Ty, bitcast);

Value c16 = createConst(op.getLoc(), i32Ty, 16, rewriter);
Value shl = b.create<arith::ShLIOp>(exti, c16);
Value result = b.create<arith::BitcastOp>(resultTy, shl);

rewriter.replaceOp(op, result);
return success();
}
};

struct BFloat16TruncFOpConverter : public OpRewritePattern<arith::TruncFOp> {
using OpRewritePattern::OpRewritePattern;
LogicalResult matchAndRewrite(arith::TruncFOp op,
PatternRewriter &rewriter) const final {
ImplicitLocOpBuilder b(op.getLoc(), rewriter);
auto operand = op.getOperand();
Type operandTy = operand.getType();
Type resultTy = op.getType();
Type operandETy = getElementTypeOrSelf(operandTy);
Type resultETy = getElementTypeOrSelf(resultTy);

if (!operandETy.isF32() || !resultETy.isBF16()) {
return rewriter.notifyMatchFailure(op, "not a trunc of f32 to bf16.");
}

Type i16Ty = b.getI16Type();
Type i32Ty = b.getI32Type();
if (auto shapedTy = dyn_cast<ShapedType>(operandTy)) {
i16Ty = shapedTy.clone(i16Ty);
i32Ty = shapedTy.clone(i32Ty);
}

Value bitcast = b.create<arith::BitcastOp>(i32Ty, operand);
Value c16 = createConst(op.getLoc(), i32Ty, 16, rewriter);
Value shl = b.create<arith::ShRUIOp>(bitcast, c16);
Value trunc = b.create<arith::TruncIOp>(i16Ty, shl);
Value result = b.create<arith::BitcastOp>(resultTy, trunc);

rewriter.replaceOp(op, result);
return success();
}
};

struct ArithExpandOpsPass
: public arith::impl::ArithExpandOpsBase<ArithExpandOpsPass> {
void runOnOperation() override {
Expand All @@ -270,21 +204,6 @@ struct ArithExpandOpsPass
arith::MaxFOp,
arith::MinFOp
>();

target.addDynamicallyLegalOp<arith::ExtFOp>(
[](arith::ExtFOp op) {
Type inETy = getElementTypeOrSelf(op.getOperand().getType());
Type outETy = getElementTypeOrSelf(op.getType());
return !(inETy.isBF16() && outETy.isF32());
});

target.addDynamicallyLegalOp<arith::TruncFOp>(
[](arith::TruncFOp op) {
Type inETy = getElementTypeOrSelf(op.getOperand().getType());
Type outETy = getElementTypeOrSelf(op.getType());
return !(inETy.isF32() && outETy.isBF16());
});

// clang-format on
if (failed(applyPartialConversion(getOperation(), target,
std::move(patterns))))
Expand All @@ -301,19 +220,12 @@ void mlir::arith::populateCeilFloorDivExpandOpsPatterns(
patterns.getContext());
}

void mlir::arith::populateExpandBFloat16Patterns(RewritePatternSet &patterns) {
patterns.add<BFloat16ExtFOpConverter, BFloat16TruncFOpConverter>(
patterns.getContext());
}

void mlir::arith::populateArithExpandOpsPatterns(RewritePatternSet &patterns) {
populateCeilFloorDivExpandOpsPatterns(patterns);
// clang-format off
patterns.add<
MaxMinFOpConverter<MaxFOp, arith::CmpFPredicate::UGT>,
MaxMinFOpConverter<MinFOp, arith::CmpFPredicate::ULT>,
BFloat16ExtFOpConverter,
BFloat16TruncFOpConverter
MaxMinFOpConverter<MinFOp, arith::CmpFPredicate::ULT>
>(patterns.getContext());
// clang-format on
}
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64 changes: 0 additions & 64 deletions mlir/test/Dialect/Arith/expand-ops.mlir
View file
Expand Up @@ -215,67 +215,3 @@ func.func @minf(%a: f32, %b: f32) -> f32 {
// CHECK-NEXT: %[[IS_NAN:.*]] = arith.cmpf uno, %[[RHS]], %[[RHS]] : f32
// CHECK-NEXT: %[[RESULT:.*]] = arith.select %[[IS_NAN]], %[[RHS]], %[[SELECT]] : f32
// CHECK-NEXT: return %[[RESULT]] : f32

// -----

func.func @extf_bf16(%arg0 : bf16) -> f32 {
%0 = arith.extf %arg0 : bf16 to f32
return %0 : f32
}

// CHECK-LABEL: @extf_bf16
// CHECK-SAME: %[[ARG0:.+]]: bf16
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[ARG0]] : bf16 to i16
// CHECK-DAG: %[[EXT:.+]] = arith.extui %[[BITCAST]] : i16 to i32
// CHECK-DAG: %[[C16:.+]] = arith.constant 16
// CHECK-DAG: %[[SHLI:.+]] = arith.shli %[[EXT]], %[[C16]]
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[SHLI]] : i32 to f32
// CHECK: return %[[BITCAST]]

// -----

func.func @extf_vector_bf16(%arg0 : vector<4xbf16>) -> vector<4xf32> {
%0 = arith.extf %arg0 : vector<4xbf16> to vector<4xf32>
return %0 : vector<4xf32>
}

// CHECK-LABEL: @extf_vector_bf16
// CHECK-SAME: %[[ARG0:.+]]: vector<4xbf16>
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[ARG0]] : vector<4xbf16> to vector<4xi16>
// CHECK-DAG: %[[EXT:.+]] = arith.extui %[[BITCAST]] : vector<4xi16> to vector<4xi32>
// CHECK-DAG: %[[C16:.+]] = arith.constant dense<16>
// CHECK-DAG: %[[SHLI:.+]] = arith.shli %[[EXT]], %[[C16]]
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[SHLI]] : vector<4xi32> to vector<4xf32>
// CHECK: return %[[BITCAST]]

// -----

func.func @truncf_f32(%arg0 : f32) -> bf16 {
%0 = arith.truncf %arg0 : f32 to bf16
return %0 : bf16
}

// CHECK-LABEL: @truncf_f32
// CHECK-SAME: %[[ARG0:.+]]: f32
// CHECK-DAG: %[[C16:.+]] = arith.constant 16
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[ARG0]] : f32 to i32
// CHECK-DAG: %[[SHR:.+]] = arith.shrui %[[BITCAST]], %[[C16]]
// CHECK-DAG: %[[TRUNC:.+]] = arith.trunci %[[SHR]] : i32 to i16
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[TRUNC]] : i16 to bf16
// CHECK: return %[[BITCAST]] : bf16

// -----

func.func @truncf_vector_f32(%arg0 : vector<4xf32>) -> vector<4xbf16> {
%0 = arith.truncf %arg0 : vector<4xf32> to vector<4xbf16>
return %0 : vector<4xbf16>
}

// CHECK-LABEL: @truncf_vector_f32
// CHECK-SAME: %[[ARG0:.+]]: vector<4xf32>
// CHECK-DAG: %[[C16:.+]] = arith.constant dense<16>
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[ARG0]] : vector<4xf32> to vector<4xi32>
// CHECK-DAG: %[[SHR:.+]] = arith.shrui %[[BITCAST]], %[[C16]]
// CHECK-DAG: %[[TRUNC:.+]] = arith.trunci %[[SHR]] : vector<4xi32> to vector<4xi16>
// CHECK-DAG: %[[BITCAST:.+]] = arith.bitcast %[[TRUNC]] : vector<4xi16> to vector<4xbf16>
// CHECK: return %[[BITCAST]] : vector<4xbf16>

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