[clang] eccf7fc - [AST] Add fixed-point subtraction constant evaluation.

Bevin Hansson via cfe-commits cfe-commits at lists.llvm.org
Fri Jun 26 04:41:55 PDT 2020


Author: Bevin Hansson
Date: 2020-06-26T13:38:11+02:00
New Revision: eccf7fc7b31a00823a0fe6c782ef312b3ba743c4

URL: https://github.com/llvm/llvm-project/commit/eccf7fc7b31a00823a0fe6c782ef312b3ba743c4
DIFF: https://github.com/llvm/llvm-project/commit/eccf7fc7b31a00823a0fe6c782ef312b3ba743c4.diff

LOG: [AST] Add fixed-point subtraction constant evaluation.

Reviewers: rjmccall, leonardchan

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73185

Added: 
    

Modified: 
    clang/include/clang/Basic/FixedPoint.h
    clang/lib/AST/ExprConstant.cpp
    clang/lib/Basic/FixedPoint.cpp
    clang/test/Frontend/fixed_point_sub.c

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/FixedPoint.h b/clang/include/clang/Basic/FixedPoint.h
index 55465c604a7d..1f3251982325 100644
--- a/clang/include/clang/Basic/FixedPoint.h
+++ b/clang/include/clang/Basic/FixedPoint.h
@@ -28,8 +28,8 @@ class QualType;
 /// The fixed point semantics work similarly to llvm::fltSemantics. The width
 /// specifies the whole bit width of the underlying scaled integer (with padding
 /// if any). The scale represents the number of fractional bits in this type.
-/// When HasUnsignedPadding is true and this type is signed, the first bit
-/// in the value this represents is treaded as padding.
+/// When HasUnsignedPadding is true and this type is unsigned, the first bit
+/// in the value this represents is treated as padding.
 class FixedPointSemantics {
 public:
   FixedPointSemantics(unsigned Width, unsigned Scale, bool IsSigned,
@@ -125,9 +125,10 @@ class APFixedPoint {
 
    // Perform binary operations on a fixed point type. The resulting fixed point
    // value will be in the common, full precision semantics that can represent
-   // the precision and ranges os both input values. See convert() for an
+   // the precision and ranges of both input values. See convert() for an
    // explanation of the Overflow parameter.
    APFixedPoint add(const APFixedPoint &Other, bool *Overflow = nullptr) const;
+   APFixedPoint sub(const APFixedPoint &Other, bool *Overflow = nullptr) const;
 
    /// Perform a unary negation (-X) on this fixed point type, taking into
    /// account saturation if applicable.

diff  --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index afae020f3dd2..5cdeb3cd0e67 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -12924,7 +12924,16 @@ bool FixedPointExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   case BO_Add: {
     bool AddOverflow, ConversionOverflow;
     APFixedPoint Result = LHSFX.add(RHSFX, &AddOverflow)
-                              .convert(ResultFXSema, &ConversionOverflow);
+                               .convert(ResultFXSema, &ConversionOverflow);
+    if ((AddOverflow || ConversionOverflow) &&
+        !HandleOverflow(Info, E, Result, E->getType()))
+      return false;
+    return Success(Result, E);
+  }
+  case BO_Sub: {
+    bool AddOverflow, ConversionOverflow;
+    APFixedPoint Result = LHSFX.sub(RHSFX, &AddOverflow)
+                               .convert(ResultFXSema, &ConversionOverflow);
     if ((AddOverflow || ConversionOverflow) &&
         !HandleOverflow(Info, E, Result, E->getType()))
       return false;

diff  --git a/clang/lib/Basic/FixedPoint.cpp b/clang/lib/Basic/FixedPoint.cpp
index 05600dfc6d21..29d532f49561 100644
--- a/clang/lib/Basic/FixedPoint.cpp
+++ b/clang/lib/Basic/FixedPoint.cpp
@@ -173,6 +173,30 @@ APFixedPoint APFixedPoint::add(const APFixedPoint &Other,
   return APFixedPoint(Result, CommonFXSema);
 }
 
+APFixedPoint APFixedPoint::sub(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;
+
+  llvm::APSInt Result;
+  if (CommonFXSema.isSaturated()) {
+    Result = CommonFXSema.isSigned() ? ThisVal.ssub_sat(OtherVal)
+                                     : ThisVal.usub_sat(OtherVal);
+  } else {
+    Result = ThisVal.isSigned() ? ThisVal.ssub_ov(OtherVal, Overflowed)
+                                : ThisVal.usub_ov(OtherVal, Overflowed);
+  }
+
+  if (Overflow)
+    *Overflow = Overflowed;
+
+  return APFixedPoint(Result, CommonFXSema);
+}
+
 void APFixedPoint::toString(llvm::SmallVectorImpl<char> &Str) const {
   llvm::APSInt Val = getValue();
   unsigned Scale = getScale();

diff  --git a/clang/test/Frontend/fixed_point_sub.c b/clang/test/Frontend/fixed_point_sub.c
index 59b2e0a43aed..1e449537ae23 100644
--- a/clang/test/Frontend/fixed_point_sub.c
+++ b/clang/test/Frontend/fixed_point_sub.c
@@ -1,6 +1,55 @@
 // RUN: %clang_cc1 -ffixed-point -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,SIGNED
 // RUN: %clang_cc1 -ffixed-point -fpadding-on-unsigned-fixed-point -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,UNSIGNED
 
+// Subtraction between 
diff erent fixed point types
+short _Accum sa_const = 1.0hk - 2.0hk;  // CHECK-DAG: @sa_const  = {{.*}}global i16 -128, align 2
+_Accum a_const = 1.0hk - 2.0k;          // CHECK-DAG: @a_const   = {{.*}}global i32 -32768, align 4
+long _Accum la_const = 1.0hk - 2.0lk;   // CHECK-DAG: @la_const  = {{.*}}global i64 -2147483648, align 8
+short _Accum sa_const2 = 0.5hr - 2.0hk; // CHECK-DAG: @sa_const2  = {{.*}}global i16 -192, align 2
+short _Accum sa_const3 = 0.5r - 2.0hk;  // CHECK-DAG: @sa_const3  = {{.*}}global i16 -192, align 2
+short _Accum sa_const4 = 0.5lr - 2.0hk; // CHECK-DAG: @sa_const4  = {{.*}}global i16 -192, align 2
+short _Accum sa_const5 = 2.0hk - 0.5lr; // CHECK-DAG: @sa_const5  = {{.*}}global i16 192, align 2
+
+// Unsigned subtraction
+unsigned short _Accum usa_const = 3.0uhk - 2.0uhk;
+// CHECK-SIGNED-DAG:   @usa_const = {{.*}}global i16 768, 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 -128, align 2
+
+// Subtraction with negative number
+short _Accum sa_const7 = 0.5hr - (-2.0hk);
+// CHECK-DAG: @sa_const7 = {{.*}}global i16 320, align 2
+
+// Int subtraction
+unsigned short _Accum usa_const2 = 2 - 0.5uhk;
+// CHECK-SIGNED-DAG:   @usa_const2 = {{.*}}global i16 640, align 2
+// CHECK-UNSIGNED-DAG: @usa_const2 = {{.*}}global i16 320, align 2
+short _Accum sa_const8 = 2 - (-0.5hk);   // CHECK-DAG: @sa_const8 = {{.*}}global i16 320, align 2
+short _Accum sa_const9 = 257 - 2.0hk;    // CHECK-DAG: @sa_const9 = {{.*}}global i16 32640, align 2
+long _Fract lf_const = 0.5lr - 1;        // CHECK-DAG: @lf_const  = {{.*}}global i32 -1073741824, align 4
+
+// Saturated subtraction
+_Sat short _Accum sat_sa_const = (_Sat short _Accum)128.0hk - (-128.0hk);
+// CHECK-DAG: @sat_sa_const = {{.*}}global i16 32767, align 2
+_Sat unsigned short _Accum sat_usa_const = (_Sat unsigned short _Accum)128.0uhk - (-128.0uhk);
+// 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 - (-128);
+// 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 - 2;
+// 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 -32768, align 2
+_Sat short _Accum sat_sa_const4 = (_Sat short _Accum)-150.0hk - 130.0lk;
+// CHECK-DAG: @sat_sa_const4 = {{.*}}global i16 -32768, align 2
+
+
 void SignedSubtraction() {
   // CHECK-LABEL: SignedSubtraction
   short _Accum sa;


        


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