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[mlir][spirv] Remove enableFastMathMode flag from SPIR-V conversion #86578

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Merged
merged 1 commit into from
Mar 26, 2024
Merged

[mlir][spirv] Remove enableFastMathMode flag from SPIR-V conversion #86578

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4 changes: 0 additions & 4 deletions mlir/include/mlir/Conversion/Passes.td
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Original file line number Diff line number Diff line change
Expand Up @@ -172,10 +172,6 @@ def ConvertArithToSPIRV : Pass<"convert-arith-to-spirv"> {
"bool", /*default=*/"true",
"Emulate narrower scalar types with 32-bit ones if not supported by "
"the target">,
Option<"enableFastMath", "enable-fast-math",
"bool", /*default=*/"false",
"Enable fast math mode (assuming no NaN and infinity for floating "
"point values) when performing conversion">
];
}

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5 changes: 0 additions & 5 deletions mlir/include/mlir/Dialect/SPIRV/Transforms/SPIRVConversion.h
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Expand Up @@ -55,11 +55,6 @@ struct SPIRVConversionOptions {
/// values will be packed into one 32-bit value to be memory efficient.
bool emulateLT32BitScalarTypes{true};

/// Whether to enable fast math mode during conversion. If true, various
/// patterns would assume no NaN/infinity numbers as inputs, and thus there
/// will be no special guards emitted to check and handle such cases.
bool enableFastMathMode{false};

/// Use 64-bit integers when converting index types.
bool use64bitIndex{false};
};
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7 changes: 3 additions & 4 deletions mlir/lib/Conversion/ArithToSPIRV/ArithToSPIRV.cpp
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Expand Up @@ -995,7 +995,7 @@ class CmpFOpNanNonePattern final : public OpConversionPattern<arith::CmpFOp> {
auto *converter = getTypeConverter<SPIRVTypeConverter>();

Value replace;
if (converter->getOptions().enableFastMathMode) {
if (bitEnumContainsAll(op.getFastmath(), arith::FastMathFlags::nnan)) {
if (op.getPredicate() == arith::CmpFPredicate::ORD) {
// Ordered comparsion checks if neither operand is NaN.
replace = spirv::ConstantOp::getOne(op.getType(), loc, rewriter);
Expand Down Expand Up @@ -1122,7 +1122,7 @@ class MinimumMaximumFOpPattern final : public OpConversionPattern<Op> {
Value spirvOp =
rewriter.create<SPIRVOp>(loc, dstType, adaptor.getOperands());

if (converter->getOptions().enableFastMathMode) {
if (bitEnumContainsAll(op.getFastmath(), arith::FastMathFlags::nnan)) {
rewriter.replaceOp(op, spirvOp);
return success();
}
Expand Down Expand Up @@ -1177,7 +1177,7 @@ class MinNumMaxNumFOpPattern final : public OpConversionPattern<Op> {
rewriter.create<SPIRVOp>(loc, dstType, adaptor.getOperands());

if (!shouldInsertNanGuards<SPIRVOp>() ||
converter->getOptions().enableFastMathMode) {
bitEnumContainsAll(op.getFastmath(), arith::FastMathFlags::nnan)) {
rewriter.replaceOp(op, spirvOp);
return success();
}
Expand Down Expand Up @@ -1286,7 +1286,6 @@ struct ConvertArithToSPIRVPass

SPIRVConversionOptions options;
options.emulateLT32BitScalarTypes = this->emulateLT32BitScalarTypes;
options.enableFastMathMode = this->enableFastMath;
SPIRVTypeConverter typeConverter(targetAttr, options);

// Use UnrealizedConversionCast as the bridge so that we don't need to pull
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14 changes: 7 additions & 7 deletions mlir/test/Conversion/ArithToSPIRV/fast-math.mlir
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@@ -1,4 +1,4 @@
// RUN: mlir-opt -split-input-file -convert-arith-to-spirv=enable-fast-math -verify-diagnostics %s | FileCheck %s
// RUN: mlir-opt -split-input-file -convert-arith-to-spirv -verify-diagnostics %s | FileCheck %s

module attributes {
spirv.target_env = #spirv.target_env<#spirv.vce<v1.0, [], []>, #spirv.resource_limits<>>
Expand All @@ -8,7 +8,7 @@ module attributes {
// CHECK-SAME: %[[LHS:.+]]: f32, %[[RHS:.+]]: f32
func.func @cmpf_ordered(%arg0 : f32, %arg1 : f32) -> i1 {
// CHECK: %[[T:.+]] = spirv.Constant true
%0 = arith.cmpf ord, %arg0, %arg1 : f32
%0 = arith.cmpf ord, %arg0, %arg1 fastmath<fast> : f32
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Is there a pass in upstream MLIR to add fastmath attributes to arith dialect ops?

We were using the spirv fast math mode downstream here: https://github.com/openxla/iree/blob/aacdd33eb57f79711ecae088dbb37c9bd17d7031/compiler/plugins/target/WebGPUSPIRV/WebGPUSPIRVTarget.cpp#L148-L159 . To adapt to this change, I think we'd want to add these attributes to all arith ops prior to running arith to spirv patterns here: https://github.com/openxla/iree/blob/aacdd33eb57f79711ecae088dbb37c9bd17d7031/compiler/src/iree/compiler/Codegen/SPIRV/ConvertToSPIRVPass.cpp#L655-L660.

So in our case, we start with modules that don't generally use fastmath, but then partway through our lowering process we specialize for one target that requires it. For that, we want this same "just use fast math" behavior, without needing to enumerate all possible ops that need an attribute ourselves.

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fastify-math pass sounds like a good idea

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Is there a pass in upstream MLIR to add fastmath attributes to arith dialect ops?

I don't think upstream have such pass, but it should be straightforward to implement such pass without enumerating specific ops. All arith ops which support fastmath are implementing ArithFastMathInterface, so pass may look something like this:

void runOnOperation() {
    getOperation()->walk([](ArithFastMathInterface iface) {
        ... set fastmath attribute
    });
}

// CHECK: return %[[T]]
return %0: i1
}
Expand All @@ -17,7 +17,7 @@ func.func @cmpf_ordered(%arg0 : f32, %arg1 : f32) -> i1 {
// CHECK-SAME: %[[LHS:.+]]: vector<4xf32>, %[[RHS:.+]]: vector<4xf32>
func.func @cmpf_unordered(%arg0 : vector<4xf32>, %arg1 : vector<4xf32>) -> vector<4xi1> {
// CHECK: %[[F:.+]] = spirv.Constant dense<false>
%0 = arith.cmpf uno, %arg0, %arg1 : vector<4xf32>
%0 = arith.cmpf uno, %arg0, %arg1 fastmath<nnan> : vector<4xf32>
// CHECK: return %[[F]]
return %0: vector<4xi1>
}
Expand All @@ -34,7 +34,7 @@ module attributes {
// CHECK-SAME: %[[LHS:.+]]: f32, %[[RHS:.+]]: f32
func.func @minimumf(%arg0 : f32, %arg1 : f32) -> f32 {
// CHECK: %[[F:.+]] = spirv.GL.FMin %[[LHS]], %[[RHS]]
%0 = arith.minimumf %arg0, %arg1 : f32
%0 = arith.minimumf %arg0, %arg1 fastmath<fast> : f32
// CHECK: return %[[F]]
return %0: f32
}
Expand All @@ -43,7 +43,7 @@ func.func @minimumf(%arg0 : f32, %arg1 : f32) -> f32 {
// CHECK-SAME: %[[LHS:.+]]: vector<4xf32>, %[[RHS:.+]]: vector<4xf32>
func.func @maximumf(%arg0 : vector<4xf32>, %arg1 : vector<4xf32>) -> vector<4xf32> {
// CHECK: %[[F:.+]] = spirv.GL.FMax %[[LHS]], %[[RHS]]
%0 = arith.maximumf %arg0, %arg1 : vector<4xf32>
%0 = arith.maximumf %arg0, %arg1 fastmath<fast> : vector<4xf32>
// CHECK: return %[[F]]
return %0: vector<4xf32>
}
Expand All @@ -52,7 +52,7 @@ func.func @maximumf(%arg0 : vector<4xf32>, %arg1 : vector<4xf32>) -> vector<4xf3
// CHECK-SAME: %[[LHS:.+]]: f32, %[[RHS:.+]]: f32
func.func @minnumf(%arg0 : f32, %arg1 : f32) -> f32 {
// CHECK: %[[F:.+]] = spirv.GL.FMin %[[LHS]], %[[RHS]]
%0 = arith.minnumf %arg0, %arg1 : f32
%0 = arith.minnumf %arg0, %arg1 fastmath<fast> : f32
// CHECK: return %[[F]]
return %0: f32
}
Expand All @@ -61,7 +61,7 @@ func.func @minnumf(%arg0 : f32, %arg1 : f32) -> f32 {
// CHECK-SAME: %[[LHS:.+]]: vector<4xf32>, %[[RHS:.+]]: vector<4xf32>
func.func @maxnumf(%arg0 : vector<4xf32>, %arg1 : vector<4xf32>) -> vector<4xf32> {
// CHECK: %[[F:.+]] = spirv.GL.FMax %[[LHS]], %[[RHS]]
%0 = arith.maxnumf %arg0, %arg1 : vector<4xf32>
%0 = arith.maxnumf %arg0, %arg1 fastmath<fast> : vector<4xf32>
// CHECK: return %[[F]]
return %0: vector<4xf32>
}
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