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[AST] Add fixed-point subtraction constant evaluation.
Reviewers: rjmccall, leonardchan Subscribers: cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D73185
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‎clang/include/clang/Basic/FixedPoint.h

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -28,8 +28,8 @@ class QualType;
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/// The fixed point semantics work similarly to llvm::fltSemantics. The width
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/// specifies the whole bit width of the underlying scaled integer (with padding
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/// if any). The scale represents the number of fractional bits in this type.
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/// When HasUnsignedPadding is true and this type is signed, the first bit
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/// in the value this represents is treaded as padding.
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/// When HasUnsignedPadding is true and this type is unsigned, the first bit
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/// in the value this represents is treated as padding.
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class FixedPointSemantics {
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public:
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FixedPointSemantics(unsigned Width, unsigned Scale, bool IsSigned,
@@ -125,9 +125,10 @@ class APFixedPoint {
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// Perform binary operations on a fixed point type. The resulting fixed point
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// value will be in the common, full precision semantics that can represent
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// the precision and ranges os both input values. See convert() for an
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// the precision and ranges of both input values. See convert() for an
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// explanation of the Overflow parameter.
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APFixedPoint add(const APFixedPoint &Other, bool *Overflow = nullptr) const;
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APFixedPoint sub(const APFixedPoint &Other, bool *Overflow = nullptr) const;
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/// Perform a unary negation (-X) on this fixed point type, taking into
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/// account saturation if applicable.

‎clang/lib/AST/ExprConstant.cpp

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -12924,7 +12924,16 @@ bool FixedPointExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
1292412924
case BO_Add: {
1292512925
bool AddOverflow, ConversionOverflow;
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APFixedPoint Result = LHSFX.add(RHSFX, &AddOverflow)
12927-
.convert(ResultFXSema, &ConversionOverflow);
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.convert(ResultFXSema, &ConversionOverflow);
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if ((AddOverflow || ConversionOverflow) &&
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!HandleOverflow(Info, E, Result, E->getType()))
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return false;
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return Success(Result, E);
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}
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case BO_Sub: {
12934+
bool AddOverflow, ConversionOverflow;
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APFixedPoint Result = LHSFX.sub(RHSFX, &AddOverflow)
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.convert(ResultFXSema, &ConversionOverflow);
1292812937
if ((AddOverflow || ConversionOverflow) &&
1292912938
!HandleOverflow(Info, E, Result, E->getType()))
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return false;

‎clang/lib/Basic/FixedPoint.cpp

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -173,6 +173,30 @@ APFixedPoint APFixedPoint::add(const APFixedPoint &Other,
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return APFixedPoint(Result, CommonFXSema);
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}
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APFixedPoint APFixedPoint::sub(const APFixedPoint &Other,
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bool *Overflow) const {
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auto CommonFXSema = Sema.getCommonSemantics(Other.getSemantics());
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APFixedPoint ConvertedThis = convert(CommonFXSema);
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APFixedPoint ConvertedOther = Other.convert(CommonFXSema);
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llvm::APSInt ThisVal = ConvertedThis.getValue();
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llvm::APSInt OtherVal = ConvertedOther.getValue();
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bool Overflowed = false;
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llvm::APSInt Result;
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if (CommonFXSema.isSaturated()) {
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Result = CommonFXSema.isSigned() ? ThisVal.ssub_sat(OtherVal)
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: ThisVal.usub_sat(OtherVal);
189+
} else {
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Result = ThisVal.isSigned() ? ThisVal.ssub_ov(OtherVal, Overflowed)
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: ThisVal.usub_ov(OtherVal, Overflowed);
192+
}
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if (Overflow)
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*Overflow = Overflowed;
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return APFixedPoint(Result, CommonFXSema);
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}
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void APFixedPoint::toString(llvm::SmallVectorImpl<char> &Str) const {
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llvm::APSInt Val = getValue();
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unsigned Scale = getScale();

‎clang/test/Frontend/fixed_point_sub.c

Lines changed: 49 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,55 @@
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// RUN: %clang_cc1 -ffixed-point -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,SIGNED
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// RUN: %clang_cc1 -ffixed-point -fpadding-on-unsigned-fixed-point -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,UNSIGNED
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4+
// Subtraction between different fixed point types
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short _Accum sa_const = 1.0hk - 2.0hk; // CHECK-DAG: @sa_const = {{.*}}global i16 -128, align 2
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_Accum a_const = 1.0hk - 2.0k; // CHECK-DAG: @a_const = {{.*}}global i32 -32768, align 4
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long _Accum la_const = 1.0hk - 2.0lk; // CHECK-DAG: @la_const = {{.*}}global i64 -2147483648, align 8
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short _Accum sa_const2 = 0.5hr - 2.0hk; // CHECK-DAG: @sa_const2 = {{.*}}global i16 -192, align 2
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short _Accum sa_const3 = 0.5r - 2.0hk; // CHECK-DAG: @sa_const3 = {{.*}}global i16 -192, align 2
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short _Accum sa_const4 = 0.5lr - 2.0hk; // CHECK-DAG: @sa_const4 = {{.*}}global i16 -192, align 2
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short _Accum sa_const5 = 2.0hk - 0.5lr; // CHECK-DAG: @sa_const5 = {{.*}}global i16 192, align 2
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// Unsigned subtraction
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unsigned short _Accum usa_const = 3.0uhk - 2.0uhk;
15+
// CHECK-SIGNED-DAG: @usa_const = {{.*}}global i16 768, align 2
16+
// CHECK-UNSIGNED-DAG: @usa_const = {{.*}}global i16 384, align 2
17+
18+
// Unsigned - signed
19+
short _Accum sa_const6 = 1.0uhk - 2.0hk;
20+
// CHECK-DAG: @sa_const6 = {{.*}}global i16 -128, align 2
21+
22+
// Subtraction with negative number
23+
short _Accum sa_const7 = 0.5hr - (-2.0hk);
24+
// CHECK-DAG: @sa_const7 = {{.*}}global i16 320, align 2
25+
26+
// Int subtraction
27+
unsigned short _Accum usa_const2 = 2 - 0.5uhk;
28+
// CHECK-SIGNED-DAG: @usa_const2 = {{.*}}global i16 640, align 2
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// CHECK-UNSIGNED-DAG: @usa_const2 = {{.*}}global i16 320, align 2
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short _Accum sa_const8 = 2 - (-0.5hk); // CHECK-DAG: @sa_const8 = {{.*}}global i16 320, align 2
31+
short _Accum sa_const9 = 257 - 2.0hk; // CHECK-DAG: @sa_const9 = {{.*}}global i16 32640, align 2
32+
long _Fract lf_const = 0.5lr - 1; // CHECK-DAG: @lf_const = {{.*}}global i32 -1073741824, align 4
33+
34+
// Saturated subtraction
35+
_Sat short _Accum sat_sa_const = (_Sat short _Accum)128.0hk - (-128.0hk);
36+
// CHECK-DAG: @sat_sa_const = {{.*}}global i16 32767, align 2
37+
_Sat unsigned short _Accum sat_usa_const = (_Sat unsigned short _Accum)128.0uhk - (-128.0uhk);
38+
// CHECK-SIGNED-DAG: @sat_usa_const = {{.*}}global i16 65535, align 2
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// CHECK-UNSIGNED-DAG: @sat_usa_const = {{.*}}global i16 32767, align 2
40+
_Sat short _Accum sat_sa_const2 = (_Sat short _Accum)128.0hk - (-128);
41+
// CHECK-DAG: @sat_sa_const2 = {{.*}}global i16 32767, align 2
42+
_Sat unsigned short _Accum sat_usa_const2 = (_Sat unsigned short _Accum)128.0uhk - (-128);
43+
// CHECK-SIGNED-DAG: @sat_usa_const2 = {{.*}}global i16 65535, align 2
44+
// CHECK-UNSIGNED-DAG: @sat_usa_const2 = {{.*}}global i16 32767, align 2
45+
_Sat unsigned short _Accum sat_usa_const3 = (_Sat unsigned short _Accum)0.5uhk - 2;
46+
// CHECK-DAG: @sat_usa_const3 = {{.*}}global i16 0, align 2
47+
_Sat short _Accum sat_sa_const3 = (_Sat short _Accum)-128.0hk - 128;
48+
// CHECK-DAG: @sat_sa_const3 = {{.*}}global i16 -32768, align 2
49+
_Sat short _Accum sat_sa_const4 = (_Sat short _Accum)-150.0hk - 130.0lk;
50+
// CHECK-DAG: @sat_sa_const4 = {{.*}}global i16 -32768, align 2
51+
52+
453
void SignedSubtraction() {
554
// CHECK-LABEL: SignedSubtraction
655
short _Accum sa;

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