[Constant Evaluator] Add support for BinaryInteger.description which

converts an integer to a string. This patch adds a @_semantics
annotation to the BinaryInteger.description function.

Author: ravikandhadai

include/swift/AST/SemanticAttrs.def

@@ -34,6 +34,8 @@ SEMANTICS_ATTR(STRING_PLUS_EQUALS, "string.plusequals")
 SEMANTICS_ATTR(FIND_STRING_SWITCH_CASE, "findStringSwitchCase")
 SEMANTICS_ATTR(FIND_STRING_SWITCH_CASE_WITH_CACHE, "findStringSwitchCaseWithCache")
 
+SEMANTICS_ATTR(BINARY_INTEGER_DESCRIPTION, "binaryInteger.description")
+
 SEMANTICS_ATTR(SWIFT_CONCURRENT_ASYNC, "swift.concurrent.async")
 SEMANTICS_ATTR(SWIFT_CONCURRENT_SAFE, "swift.concurrent.safe")
 SEMANTICS_ATTR(SWIFT_CONCURRENT, "swift.concurrent")

lib/SILOptimizer/Utils/ConstExpr.cpp

@@ -56,6 +56,8 @@ enum class WellKnownFunction {
   StringEquals,
   // String.percentEscapedString.getter
   StringEscapePercent,
+  // BinaryInteger.description.getter
+  BinaryIntegerDescription,
   // _assertionFailure(_: StaticString, _: StaticString, file: StaticString,...)
   AssertionFailure,
   // A function taking one argument that prints the symbolic value of the
@@ -83,6 +85,8 @@ static llvm::Optional<WellKnownFunction> classifyFunction(SILFunction *fn) {
     return WellKnownFunction::StringEquals;
   if (fn->hasSemanticsAttr(semantics::STRING_ESCAPE_PERCENT_GET))
     return WellKnownFunction::StringEscapePercent;
+  if (fn->hasSemanticsAttr(semantics::BINARY_INTEGER_DESCRIPTION))
+    return WellKnownFunction::BinaryIntegerDescription;
   if (fn->hasSemanticsAttrThatStartsWith("programtermination_point"))
     return WellKnownFunction::AssertionFailure;
   // A call to a function with the following semantics annotation will be
@@ -789,6 +793,28 @@ static Type getArrayElementType(Type ty) {
   return Type();
 }
 
+/// Check if the given type \p ty is a stdlib integer type and if so return
+/// whether the type is signed. Returns \c None if \p ty is not a stdlib integer
+/// type, \c true if it is a signed integer type and \c false if it is an
+/// unsigned integer type.
+static Optional<bool> getSignIfStdlibIntegerType(Type ty) {
+  StructDecl *decl = ty->getStructOrBoundGenericStruct();
+  if (!decl)
+    return None;
+  ASTContext &astCtx = ty->getASTContext();
+  if (decl == astCtx.getIntDecl() || decl == astCtx.getInt8Decl() ||
+      decl == astCtx.getInt16Decl() || decl == astCtx.getInt32Decl() ||
+      decl == astCtx.getInt64Decl()) {
+    return true;
+  }
+  if (decl == astCtx.getUIntDecl() || decl == astCtx.getUInt8Decl() ||
+      decl == astCtx.getUInt16Decl() || decl == astCtx.getUInt32Decl() ||
+      decl == astCtx.getUInt64Decl()) {
+    return false;
+  }
+  return None;
+}
+
 /// Given a call to a well known function, collect its arguments as constants,
 /// fold it, and return None.  If any of the arguments are not constants, marks
 /// the call's results as Unknown, and return an Unknown with information about
@@ -1064,6 +1090,42 @@ ConstExprFunctionState::computeWellKnownCallResult(ApplyInst *apply,
     setValue(apply, resultVal);
     return None;
   }
+  case WellKnownFunction::BinaryIntegerDescription: {
+    // BinaryInteger.description.getter
+    assert(conventions.getNumDirectSILResults() == 1 &&
+           conventions.getNumIndirectSILResults() == 0 &&
+           conventions.getNumParameters() == 1 && apply->hasSubstitutions() &&
+           "unexpected BinaryInteger.description.getter signature");
+    // Get the type of the argument and check if it is a signed or
+    // unsigned integer.
+    SILValue integerArgument = apply->getOperand(1);
+    CanType argumentType = substituteGenericParamsAndSimpify(
+        integerArgument->getType().getASTType());
+    Optional<bool> isSignedIntegerType =
+        getSignIfStdlibIntegerType(argumentType);
+    if (!isSignedIntegerType.hasValue()) {
+      return getUnknown(evaluator, (SILInstruction *)apply,
+                        UnknownReason::InvalidOperandValue);
+    }
+    // Load the stdlib integer's value and convert it to a string.
+    SymbolicValue stdlibIntegerValue =
+        getConstAddrAndLoadResult(integerArgument);
+    if (!stdlibIntegerValue.isConstant()) {
+      return stdlibIntegerValue;
+    }
+    SymbolicValue builtinIntegerValue =
+        stdlibIntegerValue.lookThroughSingleElementAggregates();
+    assert(builtinIntegerValue.getKind() == SymbolicValue::Integer &&
+           "stdlib integer type must store only a builtin integer");
+    APInt integer = builtinIntegerValue.getIntegerValue();
+    SmallString<8> integerString;
+    isSignedIntegerType.getValue() ? integer.toStringSigned(integerString)
+                                   : integer.toStringUnsigned(integerString);
+    SymbolicValue resultVal =
+        SymbolicValue::getString(integerString.str(), evaluator.getAllocator());
+    setValue(apply, resultVal);
+    return None;
+  }
   case WellKnownFunction::DebugPrint: {
     assert(apply->getNumArguments() == 1 &&
            "debug_print function must take exactly one argument");

stdlib/public/core/Integers.swift

@@ -1557,6 +1557,7 @@ extension BinaryInteger {
   }
 
   /// A textual representation of this value.
+  @_semantics("binaryInteger.description")
   public var description: String {
     return _description(radix: 10, uppercase: false)
   }

test/SILOptimizer/constant_evaluable_subset_test.swift

@@ -911,3 +911,17 @@ func interpretMetaTypeCast() -> Bool {
 func interpretMetaTypeCast2() -> Bool {
   return testMetaTypeCast(((Int) -> Int).self)
 }
+
+// CHECK-LABEL: @testBinaryIntegerDescription
+// CHECK-NOT: error:
+@_semantics("constant_evaluable")
+func testBinaryIntegerDescription<T: BinaryInteger>(_ x: T) -> String {
+  return x.description
+}
+
+@_semantics("test_driver")
+func interpretBinaryIntegerDescription() -> String {
+  var str = testBinaryIntegerDescription(-10)
+  str += testBinaryIntegerDescription(UInt(20))
+  return str
+}

test/SILOptimizer/constant_evaluator_test.sil

@@ -1503,3 +1503,31 @@ bb0:
   %3 = apply %2<Int64>(%1) : $@convention(thin) <τ_0_0> (@thick τ_0_0.Type) -> Builtin.Int1
   return %3 : $Builtin.Int1
 } // CHECK: Returns int: -1
+
+// CHECK-LABEL: @interpretBinaryIntegerDescription
+sil [ossa] @interpretBinaryIntegerDescription : $@convention(thin) () -> @owned String {
+bb0:
+  %0 = integer_literal $Builtin.Int64, -10
+  %1 = struct $Int64 (%0 : $Builtin.Int64)
+  %2 = alloc_stack $Int64
+  store %1 to [trivial] %2 : $*Int64
+  %4 = function_ref @binaryIntegerDescription : $@convention(method) <τ_0_0 where τ_0_0 : BinaryInteger> (@in_guaranteed τ_0_0) -> @owned String
+  %5 = apply %4<Int64>(%2) : $@convention(method) <τ_0_0 where τ_0_0 : BinaryInteger> (@in_guaranteed τ_0_0) -> @owned String
+  dealloc_stack %2 : $*Int64
+  return %5 : $String
+} // CHECK: Returns string: "-10"
+
+sil [_semantics "binaryInteger.description"] @binaryIntegerDescription : $@convention(method) <τ_0_0 where τ_0_0 : BinaryInteger> (@in_guaranteed τ_0_0) -> @owned String
+
+// CHECK-LABEL: @interpretUnsignedBinaryIntegerDescription
+sil [ossa] @interpretUnsignedBinaryIntegerDescription : $@convention(thin) () -> @owned String {
+bb0:
+  %0 = integer_literal $Builtin.Int64, 0xffffffffffffffff
+  %1 = struct $UInt64 (%0 : $Builtin.Int64)
+  %2 = alloc_stack $UInt64
+  store %1 to [trivial] %2 : $*UInt64
+  %4 = function_ref @binaryIntegerDescription : $@convention(method) <τ_0_0 where τ_0_0 : BinaryInteger> (@in_guaranteed τ_0_0) -> @owned String
+  %5 = apply %4<UInt64>(%2) : $@convention(method) <τ_0_0 where τ_0_0 : BinaryInteger> (@in_guaranteed τ_0_0) -> @owned String
+  dealloc_stack %2 : $*UInt64
+  return %5 : $String
+} // CHECK: Returns string: "18446744073709551615"