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[clang] Add fixed point precision macros
This defines the builtin macros specified in `7.18a.3 Precision macros` of N1169. These are the `__*__` versions of them and the formal definitions in stdfix.h can use them.
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‎clang/lib/Frontend/InitPreprocessor.cpp

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@@ -768,6 +768,59 @@ void InitializeOpenCLFeatureTestMacros(const TargetInfo &TI,
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Builder.defineMacro("__opencl_c_int64");
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}
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std::string ConstructFixedPointLiteral(llvm::APFixedPoint Val,
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llvm::StringRef Suffix) {
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if (Val.isSigned() && Val == llvm::APFixedPoint::getMin(Val.getSemantics())) {
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// When representing the min value of a signed fixed point type in source
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// code, we cannot simply write `-<lowest value>`. For example, the min
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// value of a `short _Fract` cannot be written as `-1.0hr`. This is because
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// the parser will read this (and really any negative numerical literal) as
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// a UnaryOperator that owns a FixedPointLiteral with a positive value
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// rather than just a FixedPointLiteral with a negative value. Compiling
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// `-1.0hr` results in an overflow to the maximal value of that fixed point
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// type. The correct way to represent a signed min value is to instead split
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// it into two halves, like `(-0.5hr-0.5hr)` which is what the standard
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// defines SFRACT_MIN as.
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std::string Literal;
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std::string HalfStr = ConstructFixedPointLiteral(Val.shr(1), Suffix);
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Literal.push_back('(');
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Literal += HalfStr;
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Literal += HalfStr;
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Literal.push_back(')');
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return Literal;
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}
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std::string Str(Val.toString());
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Str += Suffix;
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return Str;
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}
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void DefineFixedPointMacros(const TargetInfo &TI, MacroBuilder &Builder,
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llvm::StringRef TypeName, llvm::StringRef Suffix,
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unsigned Width, unsigned Scale, bool Signed) {
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// Saturation doesn't affect the size or scale of a fixed point type, so we
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// don't need it here.
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llvm::FixedPointSemantics FXSema(
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Width, Scale, Signed, /*IsSaturated=*/false,
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!Signed && TI.doUnsignedFixedPointTypesHavePadding());
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llvm::SmallString<32> MacroPrefix("__");
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MacroPrefix += TypeName;
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Builder.defineMacro(MacroPrefix + "_EPSILON__",
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ConstructFixedPointLiteral(
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llvm::APFixedPoint::getEpsilon(FXSema), Suffix));
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Builder.defineMacro(MacroPrefix + "_FBIT__", Twine(Scale));
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Builder.defineMacro(
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MacroPrefix + "_MAX__",
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ConstructFixedPointLiteral(llvm::APFixedPoint::getMax(FXSema), Suffix));
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// N1169 doesn't specify MIN macros for unsigned types since they're all just
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// zero.
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if (Signed)
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Builder.defineMacro(
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MacroPrefix + "_MIN__",
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ConstructFixedPointLiteral(llvm::APFixedPoint::getMin(FXSema), Suffix));
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}
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static void InitializePredefinedMacros(const TargetInfo &TI,
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const LangOptions &LangOpts,
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const FrontendOptions &FEOpts,
@@ -1097,6 +1150,47 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
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TI.getTypeWidth(TI.getIntMaxType()) &&
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"uintmax_t and intmax_t have different widths?");
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if (LangOpts.FixedPoint) {
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// Each unsigned type has the same width as their signed type.
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DefineFixedPointMacros(TI, Builder, "SFRACT", "hr", TI.getShortFractWidth(),
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TI.getShortFractScale(), /*Signed=*/true);
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DefineFixedPointMacros(TI, Builder, "USFRACT", "uhr",
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TI.getShortFractWidth(),
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TI.getUnsignedShortFractScale(), /*Signed=*/false);
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DefineFixedPointMacros(TI, Builder, "FRACT", "r", TI.getFractWidth(),
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TI.getFractScale(), /*Signed=*/true);
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DefineFixedPointMacros(TI, Builder, "UFRACT", "ur", TI.getFractWidth(),
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TI.getUnsignedFractScale(), /*Signed=*/false);
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DefineFixedPointMacros(TI, Builder, "LFRACT", "lr", TI.getLongFractWidth(),
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TI.getLongFractScale(), /*Signed=*/true);
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DefineFixedPointMacros(TI, Builder, "ULFRACT", "ulr",
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TI.getLongFractWidth(),
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TI.getUnsignedLongFractScale(), /*Signed=*/false);
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DefineFixedPointMacros(TI, Builder, "SACCUM", "hk", TI.getShortAccumWidth(),
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TI.getShortAccumScale(), /*Signed=*/true);
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DefineFixedPointMacros(TI, Builder, "USACCUM", "uhk",
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TI.getShortAccumWidth(),
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TI.getUnsignedShortAccumScale(), /*Signed=*/false);
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DefineFixedPointMacros(TI, Builder, "ACCUM", "k", TI.getAccumWidth(),
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TI.getAccumScale(), /*Signed=*/true);
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DefineFixedPointMacros(TI, Builder, "UACCUM", "uk", TI.getAccumWidth(),
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TI.getUnsignedAccumScale(), /*Signed=*/false);
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DefineFixedPointMacros(TI, Builder, "LACCUM", "lk", TI.getLongAccumWidth(),
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TI.getLongAccumScale(), /*Signed=*/true);
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DefineFixedPointMacros(TI, Builder, "ULACCUM", "ulk",
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TI.getLongAccumWidth(),
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TI.getUnsignedLongAccumScale(), /*Signed=*/false);
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Builder.defineMacro("__SACCUM_IBIT__", Twine(TI.getShortAccumIBits()));
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Builder.defineMacro("__USACCUM_IBIT__",
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Twine(TI.getUnsignedShortAccumIBits()));
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Builder.defineMacro("__ACCUM_IBIT__", Twine(TI.getAccumIBits()));
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Builder.defineMacro("__UACCUM_IBIT__", Twine(TI.getUnsignedAccumIBits()));
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Builder.defineMacro("__LACCUM_IBIT__", Twine(TI.getLongAccumIBits()));
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Builder.defineMacro("__ULACCUM_IBIT__",
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Twine(TI.getUnsignedLongAccumIBits()));
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}
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if (TI.hasFloat16Type())
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DefineFloatMacros(Builder, "FLT16", &TI.getHalfFormat(), "F16");
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DefineFloatMacros(Builder, "FLT", &TI.getFloatFormat(), "F");

‎clang/test/Preprocessor/fixed-point.c

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@@ -0,0 +1,67 @@
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/// Assert the fixed point precision macros according to N1169 7.18a.3 are
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/// defined when -ffixed-point is provided.
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// RUN: %clang_cc1 -triple=x86_64 -E -dM -ffixed-point -x c < /dev/null | FileCheck -match-full-lines %s
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// RUN: %clang_cc1 -triple=x86_64 -E -dM -ffixed-point -x c++ < /dev/null | FileCheck -match-full-lines %s
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/// These are the implementation-defined values for x86_64.
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// CHECK-DAG:#define __SFRACT_EPSILON__ 0.0078125hr
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// CHECK-DAG:#define __SFRACT_FBIT__ 7
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// CHECK-DAG:#define __SFRACT_MAX__ 0.9921875hr
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// CHECK-DAG:#define __SFRACT_MIN__ (-0.5hr-0.5hr)
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// CHECK-DAG:#define __USFRACT_EPSILON__ 0.00390625uhr
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// CHECK-DAG:#define __USFRACT_FBIT__ 8
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// CHECK-DAG:#define __USFRACT_MAX__ 0.99609375uhr
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// CHECK-DAG:#define __FRACT_EPSILON__ 0.000030517578125r
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// CHECK-DAG:#define __FRACT_FBIT__ 15
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// CHECK-DAG:#define __FRACT_MAX__ 0.999969482421875r
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// CHECK-DAG:#define __FRACT_MIN__ (-0.5r-0.5r)
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// CHECK-DAG:#define __UFRACT_EPSILON__ 0.0000152587890625ur
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// CHECK-DAG:#define __UFRACT_FBIT__ 16
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// CHECK-DAG:#define __UFRACT_MAX__ 0.9999847412109375ur
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// CHECK-DAG:#define __LFRACT_EPSILON__ 0.0000000004656612873077392578125lr
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// CHECK-DAG:#define __LFRACT_FBIT__ 31
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// CHECK-DAG:#define __LFRACT_MAX__ 0.9999999995343387126922607421875lr
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// CHECK-DAG:#define __LFRACT_MIN__ (-0.5lr-0.5lr)
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// CHECK-DAG:#define __ULFRACT_EPSILON__ 0.00000000023283064365386962890625ulr
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// CHECK-DAG:#define __ULFRACT_FBIT__ 32
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// CHECK-DAG:#define __ULFRACT_MAX__ 0.99999999976716935634613037109375ulr
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// CHECK-DAG:#define __SACCUM_EPSILON__ 0.0078125hk
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// CHECK-DAG:#define __SACCUM_FBIT__ 7
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// CHECK-DAG:#define __SACCUM_MAX__ 255.9921875hk
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// CHECK-DAG:#define __SACCUM_MIN__ (-128.0hk-128.0hk)
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// CHECK-DAG:#define __USACCUM_EPSILON__ 0.00390625uhk
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// CHECK-DAG:#define __USACCUM_FBIT__ 8
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// CHECK-DAG:#define __USACCUM_MAX__ 255.99609375uhk
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// CHECK-DAG:#define __ACCUM_EPSILON__ 0.000030517578125k
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// CHECK-DAG:#define __ACCUM_FBIT__ 15
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// CHECK-DAG:#define __ACCUM_MAX__ 65535.999969482421875k
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// CHECK-DAG:#define __ACCUM_MIN__ (-32768.0k-32768.0k)
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// CHECK-DAG:#define __UACCUM_EPSILON__ 0.0000152587890625uk
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// CHECK-DAG:#define __UACCUM_FBIT__ 16
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// CHECK-DAG:#define __UACCUM_MAX__ 65535.9999847412109375uk
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// CHECK-DAG:#define __LACCUM_EPSILON__ 0.0000000004656612873077392578125lk
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// CHECK-DAG:#define __LACCUM_FBIT__ 31
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// CHECK-DAG:#define __LACCUM_MAX__ 4294967295.9999999995343387126922607421875lk
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// CHECK-DAG:#define __LACCUM_MIN__ (-2147483648.0lk-2147483648.0lk)
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// CHECK-DAG:#define __ULACCUM_EPSILON__ 0.00000000023283064365386962890625ulk
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// CHECK-DAG:#define __ULACCUM_FBIT__ 32
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// CHECK-DAG:#define __ULACCUM_MAX__ 4294967295.99999999976716935634613037109375ulk
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// CHECK-DAG:#define __SACCUM_IBIT__ 8
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// CHECK-DAG:#define __USACCUM_IBIT__ 8
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// CHECK-DAG:#define __ACCUM_IBIT__ 16
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// CHECK-DAG:#define __UACCUM_IBIT__ 16
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// CHECK-DAG:#define __LACCUM_IBIT__ 32
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// CHECK-DAG:#define __ULACCUM_IBIT__ 32

‎clang/test/Preprocessor/no-fixed-point.c

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@@ -0,0 +1,7 @@
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/// Assert the fixed point precision macros according to N1169 7.18a.3 are not
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/// defined when -ffixed-point is not provided.
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// RUN: %clang_cc1 -triple=x86_64 -E -dM -x c < /dev/null | FileCheck -match-full-lines %s
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// RUN: %clang_cc1 -triple=x86_64 -E -dM -x c++ < /dev/null | FileCheck -match-full-lines %s
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// CHECK-NOT:#define __SFRACT_FBIT__ 7

‎llvm/include/llvm/ADT/APFixedPoint.h

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@@ -260,6 +260,7 @@ class APFixedPoint {
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static APFixedPoint getMax(const FixedPointSemantics &Sema);
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static APFixedPoint getMin(const FixedPointSemantics &Sema);
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static APFixedPoint getEpsilon(const FixedPointSemantics &Sema);
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/// Given a floating point semantic, return the next floating point semantic
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/// with a larger exponent and larger or equal mantissa.

‎llvm/lib/Support/APFixedPoint.cpp

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@@ -129,6 +129,12 @@ APFixedPoint APFixedPoint::getMin(const FixedPointSemantics &Sema) {
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return APFixedPoint(Val, Sema);
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}
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APFixedPoint APFixedPoint::getEpsilon(const FixedPointSemantics &Sema) {
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APSInt Val(Sema.getWidth(), !Sema.isSigned());
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Val.setBit(/*BitPosition=*/0);
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return APFixedPoint(Val, Sema);
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}
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bool FixedPointSemantics::fitsInFloatSemantics(
133139
const fltSemantics &FloatSema) const {
134140
// A fixed point semantic fits in a floating point semantic if the maximum

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