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[AST] Add fixed-point division constant evaluation. 

Reviewers: rjmccall, leonardchan, bjope

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73187
This commit is contained in:
Bevin Hansson 2020-01-22 10:10:54 +01:00
parent 53f5c8b4a1
commit 94e8ec631d
4 changed files with 129 additions and 0 deletions
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1
clang/include/clang/Basic/FixedPoint.h
View File

@ -130,6 +130,7 @@ class APFixedPoint {
APFixedPoint add(const APFixedPoint &Other, bool *Overflow = nullptr) const;
APFixedPoint sub(const APFixedPoint &Other, bool *Overflow = nullptr) const;
APFixedPoint mul(const APFixedPoint &Other, bool *Overflow = nullptr) const;
APFixedPoint div(const APFixedPoint &Other, bool *Overflow = nullptr) const;
/// Perform a unary negation (-X) on this fixed point type, taking into
/// account saturation if applicable.

9
clang/lib/AST/ExprConstant.cpp
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@ -12948,6 +12948,15 @@ bool FixedPointExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
return false;
return Success(Result, E);
}
case BO_Div: {
bool AddOverflow, ConversionOverflow;
APFixedPoint Result = LHSFX.div(RHSFX, &AddOverflow)
.convert(ResultFXSema, &ConversionOverflow);
if ((AddOverflow || ConversionOverflow) &&
!HandleOverflow(Info, E, Result, E->getType()))
return false;
return Success(Result, E);
}
default:
return false;
}

55
clang/lib/Basic/FixedPoint.cpp
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@ -254,6 +254,61 @@ APFixedPoint APFixedPoint::mul(const APFixedPoint &Other,
CommonFXSema);
}
APFixedPoint APFixedPoint::div(const APFixedPoint &Other,
bool *Overflow) const {
auto CommonFXSema = Sema.getCommonSemantics(Other.getSemantics());
APFixedPoint ConvertedThis = convert(CommonFXSema);
APFixedPoint ConvertedOther = Other.convert(CommonFXSema);
llvm::APSInt ThisVal = ConvertedThis.getValue();
llvm::APSInt OtherVal = ConvertedOther.getValue();
bool Overflowed = false;
// Widen the LHS and RHS so we can perform a full division.
unsigned Wide = CommonFXSema.getWidth() * 2;
if (CommonFXSema.isSigned()) {
ThisVal = ThisVal.sextOrSelf(Wide);
OtherVal = OtherVal.sextOrSelf(Wide);
} else {
ThisVal = ThisVal.zextOrSelf(Wide);
OtherVal = OtherVal.zextOrSelf(Wide);
}
// Upscale to compensate for the loss of precision from division, and
// perform the full division.
ThisVal = ThisVal.shl(CommonFXSema.getScale());
llvm::APSInt Result;
if (CommonFXSema.isSigned()) {
llvm::APInt Rem;
llvm::APInt::sdivrem(ThisVal, OtherVal, Result, Rem);
// If the quotient is negative and the remainder is nonzero, round
// towards negative infinity by subtracting epsilon from the result.
if (Result.isNegative() && !Rem.isNullValue())
Result = Result - 1;
} else
Result = ThisVal.udiv(OtherVal);
Result.setIsSigned(CommonFXSema.isSigned());
// If our result lies outside of the representative range of the common
// semantic, we either have overflow or saturation.
llvm::APSInt Max = APFixedPoint::getMax(CommonFXSema).getValue()
.extOrTrunc(Wide);
llvm::APSInt Min = APFixedPoint::getMin(CommonFXSema).getValue()
.extOrTrunc(Wide);
if (CommonFXSema.isSaturated()) {
if (Result < Min)
Result = Min;
else if (Result > Max)
Result = Max;
} else
Overflowed = Result < Min || Result > Max;
if (Overflow)
*Overflow = Overflowed;
return APFixedPoint(Result.sextOrTrunc(CommonFXSema.getWidth()),
CommonFXSema);
}
void APFixedPoint::toString(llvm::SmallVectorImpl<char> &Str) const {
llvm::APSInt Val = getValue();
unsigned Scale = getScale();

64
clang/test/Frontend/fixed_point_div.c
View File

@ -1,6 +1,70 @@
// RUN: %clang_cc1 -ffixed-point -triple x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,SIGNED
// RUN: %clang_cc1 -ffixed-point -triple x86_64-unknown-linux-gnu -fpadding-on-unsigned-fixed-point -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,UNSIGNED
// Division between different fixed point types
short _Accum sa_const = 1.0hk / 2.0hk; // CHECK-DAG: @sa_const = {{.*}}global i16 64, align 2
_Accum a_const = 1.0hk / 2.0k; // CHECK-DAG: @a_const = {{.*}}global i32 16384, align 4
long _Accum la_const = 1.0hk / 2.0lk; // CHECK-DAG: @la_const = {{.*}}global i64 1073741824, align 8
short _Accum sa_const2 = 0.5hr / 2.0hk; // CHECK-DAG: @sa_const2 = {{.*}}global i16 32, align 2
short _Accum sa_const3 = 0.5r / 2.0hk; // CHECK-DAG: @sa_const3 = {{.*}}global i16 32, align 2
short _Accum sa_const4 = 0.5lr / 2.0hk; // CHECK-DAG: @sa_const4 = {{.*}}global i16 32, align 2
short _Accum sa_const5 = 2.0hk / 0.5lr; // CHECK-DAG: @sa_const5 = {{.*}}global i16 512, align 2
// Unsigned division
unsigned short _Accum usa_const = 3.0uhk / 2.0uhk;
// CHECK-SIGNED-DAG: @usa_const = {{.*}}global i16 192, align 2
// CHECK-UNSIGNED-DAG: @usa_const = {{.*}}global i16 384, align 2
// Unsigned / signed
short _Accum sa_const6 = 1.0uhk / 2.0hk;
// CHECK-DAG: @sa_const6 = {{.*}}global i16 64, align 2
// Division with negative number
short _Accum sa_const7 = 0.5hr / (-2.0hk);
// CHECK-DAG: @sa_const7 = {{.*}}global i16 -32, align 2
// Int division
unsigned short _Accum usa_const2 = 2 / 0.5uhk;
// CHECK-SIGNED-DAG: @usa_const2 = {{.*}}global i16 512, align 2
// CHECK-UNSIGNED-DAG: @usa_const2 = {{.*}}global i16 1024, align 2
short _Accum sa_const8 = 2 / (-0.5hk); // CHECK-DAG: @sa_const8 = {{.*}}global i16 -512, align 2
short _Accum sa_const9 = 256 / 2.0hk; // CHECK-DAG: @sa_const9 = {{.*}}global i16 16384, align 2
long _Fract lf_const = 0.5lr / -1; // CHECK-DAG: @lf_const = {{.*}}global i32 -1073741824, align 4
// Saturated division
_Sat short _Accum sat_sa_const = (_Sat short _Accum)128.0hk / (-0.25hk);
// CHECK-DAG: @sat_sa_const = {{.*}}global i16 -32768, align 2
_Sat unsigned short _Accum sat_usa_const = (_Sat unsigned short _Accum)128.0uhk / (0.25uhk);
// CHECK-SIGNED-DAG: @sat_usa_const = {{.*}}global i16 65535, align 2
// CHECK-UNSIGNED-DAG: @sat_usa_const = {{.*}}global i16 32767, align 2
_Sat short _Accum sat_sa_const2 = (_Sat short _Accum)-128.0hk / (-0.0125hr);
// CHECK-DAG: @sat_sa_const2 = {{.*}}global i16 32767, align 2
_Sat unsigned short _Accum sat_usa_const2 = (_Sat unsigned short _Accum)128.0uhk / (-128);
// CHECK-SIGNED-DAG: @sat_usa_const2 = {{.*}}global i16 65535, align 2
// CHECK-UNSIGNED-DAG: @sat_usa_const2 = {{.*}}global i16 32767, align 2
_Sat unsigned short _Accum sat_usa_const3 = (_Sat unsigned short _Accum)0.5uhk / -1;
// CHECK-DAG: @sat_usa_const3 = {{.*}}global i16 0, align 2
_Sat short _Accum sat_sa_const3 = (_Sat short _Accum)-128.0hk / 128;
// CHECK-DAG: @sat_sa_const3 = {{.*}}global i16 -128, align 2
_Sat short _Accum sat_sa_const4 = (_Sat short _Accum)-25.7hk / 0.1lk;
// CHECK-DAG: @sat_sa_const4 = {{.*}}global i16 -32768, align 2
// Some more cases
short _Accum sa_const10 = 255.9921875hk / 255.9921875hk;
// CHECK-DAG: @sa_const10 = {{.*}}global i16 128, align 2
short _Accum sat_sa_const5 = (_Sat short _Accum)(-255.0hk - 1.0hk) / 0.0078125hk;
// CHECK-DAG: @sat_sa_const5 = {{.*}}global i16 -32768, align 2
_Sat short _Accum sat_sa_const6 = (_Sat short _Accum)(-255.0hk - 1.0hk) / -0.0078125hk;
// CHECK-DAG: @sat_sa_const6 = {{.*}}global i16 32767, align 2
short _Accum sa_const12 = 255.9921875hk / -1.0hk;
// CHECK-DAG: @sa_const12 = {{.*}}global i16 -32767, align 2
_Sat short _Accum sat_sa_const7 = (_Sat short _Accum)(-255.0hk - 1.0hk) / -1.0hk;
// CHECK-DAG: @sat_sa_const7 = {{.*}}global i16 32767, align 2
short _Accum sa_const13 = 0.0234375hk / 2.0hk;
// CHECK-DAG: @sa_const13 = {{.*}}global i16 1, align 2
short _Accum sa_const14 = -0.0234375hk / 2.0hk;
// CHECK-DAG: @sa_const14 = {{.*}}global i16 -2, align 2
void SignedDivision() {
// CHECK-LABEL: SignedDivision
short _Accum sa;