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[mlir][Parser] Use APFloat instead of FloatAttr when parsing DenseElementsAttrs. 

Summary: DenseElementsAttr stores float values as raw bits internally, so creating attributes just to have them unwrapped is extremely inefficient.

Differential Revision: https://reviews.llvm.org/D74818
This commit is contained in:
River Riddle 2020-02-19 10:28:53 -08:00
parent 6b6c96695c
commit 4a7364f1c2
1 changed files with 21 additions and 15 deletions
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36
mlir/lib/Parser/Parser.cpp
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@ -1734,22 +1734,19 @@ Attribute Parser::parseFloatAttr(Type type, bool isNegative) {
}
/// Construct a float attribute bitwise equivalent to the integer literal.
static FloatAttr buildHexadecimalFloatLiteral(Parser *p, FloatType type,
uint64_t value) {
static Optional<APFloat> buildHexadecimalFloatLiteral(Parser *p, FloatType type,
uint64_t value) {
// FIXME: bfloat is currently stored as a double internally because it doesn't
// have valid APFloat semantics.
if (type.isF64() || type.isBF16()) {
APFloat apFloat(type.getFloatSemantics(), APInt(/*numBits=*/64, value));
return p->builder.getFloatAttr(type, apFloat);
}
if (type.isF64() || type.isBF16())
return APFloat(type.getFloatSemantics(), APInt(/*numBits=*/64, value));
APInt apInt(type.getWidth(), value);
if (apInt != value) {
p->emitError("hexadecimal float constant out of range for type");
return nullptr;
return llvm::None;
}
APFloat apFloat(type.getFloatSemantics(), apInt);
return p->builder.getFloatAttr(type, apFloat);
return APFloat(type.getFloatSemantics(), apInt);
}
/// Parse a decimal or a hexadecimal literal, which can be either an integer
@ -1787,7 +1784,9 @@ Attribute Parser::parseDecOrHexAttr(Type type, bool isNegative) {
}
// Construct a float attribute bitwise equivalent to the integer literal.
return buildHexadecimalFloatLiteral(this, floatType, *val);
Optional<APFloat> apVal =
buildHexadecimalFloatLiteral(this, floatType, *val);
return apVal ? FloatAttr::get(floatType, *apVal) : Attribute();
}
if (!type.isIntOrIndex())
@ -1996,7 +1995,7 @@ DenseElementsAttr TensorLiteralParser::getIntAttr(llvm::SMLoc loc,
DenseElementsAttr TensorLiteralParser::getFloatAttr(llvm::SMLoc loc,
ShapedType type,
FloatType eltTy) {
std::vector<Attribute> floatValues;
std::vector<APFloat> floatValues;
floatValues.reserve(storage.size());
for (const auto &signAndToken : storage) {
bool isNegative = signAndToken.first;
@ -2014,10 +2013,10 @@ DenseElementsAttr TensorLiteralParser::getFloatAttr(llvm::SMLoc loc,
p.emitError("hexadecimal float constant out of range for attribute");
return nullptr;
}
FloatAttr attr = buildHexadecimalFloatLiteral(&p, eltTy, *val);
if (!attr)
Optional<APFloat> apVal = buildHexadecimalFloatLiteral(&p, eltTy, *val);
if (!apVal)
return nullptr;
floatValues.push_back(attr);
floatValues.push_back(*apVal);
continue;
}
@ -2033,7 +2032,14 @@ DenseElementsAttr TensorLiteralParser::getFloatAttr(llvm::SMLoc loc,
p.emitError("floating point value too large for attribute");
return nullptr;
}
floatValues.push_back(FloatAttr::get(eltTy, isNegative ? -*val : *val));
// Treat BF16 as double because it is not supported in LLVM's APFloat.
APFloat apVal(isNegative ? -*val : *val);
if (!eltTy.isBF16() && !eltTy.isF64()) {
bool unused;
apVal.convert(eltTy.getFloatSemantics(), APFloat::rmNearestTiesToEven,
&unused);
}
floatValues.push_back(apVal);
}
return DenseElementsAttr::get(type, floatValues);