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[mlir][tosa] Fix mul folder conformance to the spec #137601

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Merged
merged 1 commit into from
May 8, 2025
Merged

[mlir][tosa] Fix mul folder conformance to the spec #137601

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31 changes: 25 additions & 6 deletions mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -918,6 +918,27 @@ OpFoldResult IntDivOp::fold(FoldAdaptor adaptor) {
}

namespace {
// calculate lhs * rhs >> shift according to TOSA Spec
// return nullopt if result is not in range of int32_t when shift > 0
std::optional<APInt> mulInt(APInt lhs, APInt rhs, int32_t shift,
unsigned bitwidth) {
APInt result = lhs.sext(64) * rhs.sext(64);

if (shift > 0) {
auto round = APInt(64, 1) << (shift - 1);
result += round;
result.ashrInPlace(shift);
// REQUIRE(product >= minimum_s<i32_t>() && product <= maximum_s<i32_t>())
if (!(result.getSExtValue() >= INT32_MIN &&
result.getSExtValue() <= INT32_MAX)) {
// REQUIRE failed
return std::nullopt;
}
}

return result.trunc(bitwidth);
}

DenseElementsAttr mulBinaryFolder(DenseElementsAttr lhs, DenseElementsAttr rhs,
RankedTensorType ty, int32_t shift) {
if (rhs && lhs && rhs.isSplat() && lhs.isSplat()) {
Expand All @@ -930,12 +951,10 @@ DenseElementsAttr mulBinaryFolder(DenseElementsAttr lhs, DenseElementsAttr rhs,
}

auto bitwidth = ty.getElementType().getIntOrFloatBitWidth();
l = l.sext(bitwidth * 2);
r = r.sext(bitwidth * 2);
auto result = l * r;
result.lshrInPlace(shift);
result = result.trunc(bitwidth);
return DenseElementsAttr::get(ty, result);
const std::optional<APInt> result = mulInt(l, r, shift, bitwidth);
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LGTM, reviewed

if (!result)
return {};
return DenseElementsAttr::get(ty, result.value());
}

if (llvm::isa<FloatType>(ty.getElementType())) {
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41 changes: 40 additions & 1 deletion mlir/test/Dialect/Tosa/canonicalize.mlir
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Expand Up @@ -1226,4 +1226,43 @@ func.func @slice_dynamic_size_static_output_canonicalize(%arg0: tensor<2x60x59x?
%1 = tosa.const_shape {values = dense<[-1, 60, 58, -1]> : tensor<4xindex>} : () -> !tosa.shape<4>
%2 = tosa.slice %arg0, %0, %1 : (tensor<2x60x59x?xf32>, !tosa.shape<4>, !tosa.shape<4>) -> tensor<2x60x58x?xf32>
return %2 : tensor<2x60x58x?xf32>
}
}

// -----

// CHECK-LABEL: @fold_mul_shift
// CHECK-DAG: "tosa.const"() <{values = dense<1> : tensor<i32>}> : () -> tensor<i32>
func.func @fold_mul_shift() -> tensor<i32> {
%0 = "tosa.const"() <{values = dense<-23661> : tensor<i32>}> : () -> tensor<i32>
%1 = "tosa.const"() <{values = dense<-33022> : tensor<i32>}> : () -> tensor<i32>
%2 = "tosa.const"() <{values = dense<30> : tensor<1xi8>}> : () -> tensor<1xi8>
%3 = tosa.mul %0, %1, %2 : (tensor<i32>, tensor<i32>, tensor<1xi8>) -> tensor<i32>
return %3 : tensor<i32>
}

// -----

// CHECK-LABEL: @fold_mul_no_shift
// CHECK-DAG: "tosa.const"() <{values = dense<781333542> : tensor<i32>}> : () -> tensor<i32>
func.func @fold_mul_no_shift() -> tensor<i32> {
%0 = "tosa.const"() <{values = dense<-23661> : tensor<i32>}> : () -> tensor<i32>
%1 = "tosa.const"() <{values = dense<-33022> : tensor<i32>}> : () -> tensor<i32>
%2 = "tosa.const"() <{values = dense<0> : tensor<1xi8>}> : () -> tensor<1xi8>
%3 = tosa.mul %0, %1, %2 : (tensor<i32>, tensor<i32>, tensor<1xi8>) -> tensor<i32>
return %3 : tensor<i32>
}

// -----

// CHECK-LABEL: @no_fold_mul_result_exceeds_i32
// CHECK-DAG: %[[LHS:.*]] = "tosa.const"() <{values = dense<23661> : tensor<i32>}> : () -> tensor<i32>
// CHECK-DAG: %[[RHS:.*]] = "tosa.const"() <{values = dense<330222> : tensor<i32>}> : () -> tensor<i32>
// CHECK-DAG: %[[SHIFT:.*]] = "tosa.const"() <{values = dense<1> : tensor<1xi8>}> : () -> tensor<1xi8>
// CHECK: tosa.mul %[[LHS]], %[[RHS]], %[[SHIFT]] : (tensor<i32>, tensor<i32>, tensor<1xi8>) -> tensor<i32>
func.func @no_fold_mul_result_exceeds_i32() -> tensor<i32> {
%0 = "tosa.const"() <{values = dense<23661> : tensor<i32>}> : () -> tensor<i32>
%1 = "tosa.const"() <{values = dense<330222> : tensor<i32>}> : () -> tensor<i32>
%2 = "tosa.const"() <{values = dense<1> : tensor<1xi8>}> : () -> tensor<1xi8>
%3 = tosa.mul %0, %1, %2 : (tensor<i32>, tensor<i32>, tensor<1xi8>) -> tensor<i32>
return %3 : tensor<i32>
}