Revert "Remove apparently obsolete builtin functions (#20947)" (#20975)

This reverts commit b914464, which passed the public CI bots, but broke some tests on watchOS.

Author: stephentyrone

include/swift/AST/Builtins.def

@@ -478,6 +478,14 @@ BUILTIN_MISC_OPERATION(SToSCheckedTrunc, "s_to_s_checked_trunc", "n", Special)
 BUILTIN_MISC_OPERATION(SToUCheckedTrunc, "s_to_u_checked_trunc", "n", Special)
 BUILTIN_MISC_OPERATION(UToUCheckedTrunc, "u_to_u_checked_trunc", "n", Special)
 
+/// Checked conversions for signed <-> unsigned integers of the same size.
+/// Returns a tuple containing the conversion result as well as
+/// the sign error / overflow bit.
+BUILTIN_MISC_OPERATION(SUCheckedConversion,
+                       "s_to_u_checked_conversion", "n", Special)
+BUILTIN_MISC_OPERATION(USCheckedConversion,
+                       "u_to_s_checked_conversion", "n", Special)
+
 /// IntToFPWithOverflow has type (Integer) -> Float
 BUILTIN_MISC_OPERATION(IntToFPWithOverflow, "itofp_with_overflow", "n", Special)
 

include/swift/SIL/PatternMatch.h

@@ -715,6 +715,13 @@ using BuiltinApplyTy = typename Apply_match<BuiltinValueKind, Tys...>::Ty;
 // if any of the sub-matchers succeed.
 //
 
+/// Matcher for any of the builtin checked conversions.
+template <typename T0>
+inline typename OneOf_match<BuiltinApplyTy<T0>, BuiltinApplyTy<T0>>::Ty
+m_CheckedConversion(const T0 &Op0) {
+  return m_USCheckedConversion(Op0) || m_SUCheckedConversion(Op0);
+}
+
 /// Matcher for any of the builtin ExtOrBitCast instructions.
 template <typename T0>
 inline typename OneOf_match<BuiltinApplyTy<T0>, BuiltinApplyTy<T0>>::Ty

lib/AST/Builtins.cpp

@@ -1106,6 +1106,19 @@ static ValueDecl *getCheckedTruncOperation(ASTContext &Context, Identifier Id,
   return getBuiltinFunction(Id, { InTy }, ResultTy);
 }
 
+static ValueDecl *getCheckedConversionOperation(ASTContext &Context,
+                                                Identifier Id,
+                                                Type Ty) {
+  Type BuiltinTy = Ty->getAs<BuiltinIntegerType>();
+  if (!BuiltinTy)
+    return nullptr;
+
+  Type SignErrorBitTy = BuiltinIntegerType::get(1, Context);
+  TupleTypeElt ResultElts[] = { BuiltinTy, SignErrorBitTy };
+  Type ResultTy = TupleType::get(ResultElts, Context);
+  return getBuiltinFunction(Id, { BuiltinTy }, ResultTy);
+}
+
 static ValueDecl *getIntToFPWithOverflowOperation(ASTContext &Context,
                                                   Identifier Id, Type InputTy,
                                                   Type OutputTy) {
@@ -1840,6 +1853,11 @@ ValueDecl *swift::getBuiltinValueDecl(ASTContext &Context, Identifier Id) {
     if (Types.size() != 2) return nullptr;
     return getCheckedTruncOperation(Context, Id, Types[0], Types[1], false);
 
+  case BuiltinValueKind::SUCheckedConversion:
+  case BuiltinValueKind::USCheckedConversion:
+    if (Types.size() != 1) return nullptr;
+    return getCheckedConversionOperation(Context, Id, Types[0]);
+
   case BuiltinValueKind::ClassifyBridgeObject:
     if (!Types.empty()) return nullptr;
     return getClassifyBridgeObject(Context, Id);

lib/IRGen/GenBuiltin.cpp

@@ -758,6 +758,22 @@ if (Builtin.ID == BuiltinValueKind::id) { \
     return out.add(OverflowFlag);
   }
 
+  if (Builtin.ID == BuiltinValueKind::SUCheckedConversion ||
+      Builtin.ID == BuiltinValueKind::USCheckedConversion) {
+    auto Ty =
+      IGF.IGM.getStorageTypeForLowered(Builtin.Types[0]->getCanonicalType());
+
+    // Report a sign error if the input parameter is a negative number, when
+    // interpreted as signed.
+    llvm::Value *Arg = args.claimNext();
+    llvm::Value *Zero = llvm::ConstantInt::get(Ty, 0);
+    llvm::Value *OverflowFlag = IGF.Builder.CreateICmpSLT(Arg, Zero);
+
+    // Return the tuple: (the result (same as input), the overflow flag).
+    out.add(Arg);
+    return out.add(OverflowFlag);
+  }
+
   // We are currently emitting code for '_convertFromBuiltinIntegerLiteral',
   // which will call the builtin and pass it a non-compile-time-const parameter.
   if (Builtin.ID == BuiltinValueKind::IntToFPWithOverflow) {

lib/SIL/OperandOwnership.cpp

@@ -1122,6 +1122,7 @@ CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, SRem)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, SSubOver)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, SToSCheckedTrunc)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, SToUCheckedTrunc)
+CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, SUCheckedConversion)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, Shl)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, Sizeof)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, StaticReport)
@@ -1139,6 +1140,7 @@ CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, UDiv)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, UIToFP)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, UMulOver)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, URem)
+CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, USCheckedConversion)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, USubOver)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, UToSCheckedTrunc)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, MustBeLive, UToUCheckedTrunc)

lib/SIL/ValueOwnership.cpp

@@ -479,6 +479,8 @@ CONSTANT_OWNERSHIP_BUILTIN(Trivial, UToSCheckedTrunc)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, SToSCheckedTrunc)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, SToUCheckedTrunc)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, UToUCheckedTrunc)
+CONSTANT_OWNERSHIP_BUILTIN(Trivial, SUCheckedConversion)
+CONSTANT_OWNERSHIP_BUILTIN(Trivial, USCheckedConversion)
 CONSTANT_OWNERSHIP_BUILTIN(Trivial, IntToFPWithOverflow)
 
 // This is surprising, Builtin.unreachable returns a "Never" value which is

lib/SILOptimizer/Analysis/SimplifyInstruction.cpp

@@ -492,6 +492,18 @@ static SILValue simplifyBuiltin(BuiltinInst *BI) {
         return Result;
     }
 
+    // trunc(tuple_extract(conversion(extOrBitCast(x))))) -> x
+    if (match(Op, m_TupleExtractInst(
+                   m_CheckedConversion(
+                     m_ExtOrBitCast(m_SILValue(Result))), 0))) {
+      // If the top bit of Result is known to be 0, then
+      // it is safe to replace the whole pattern by original bits of x
+      if (Result->getType() == BI->getType()) {
+        if (auto signBit = computeSignBit(Result))
+          if (!signBit.getValue())
+            return Result;
+      }
+    }
     return SILValue();
   }
 
@@ -627,6 +639,23 @@ SILValue InstSimplifier::simplifyOverflowBuiltin(BuiltinInst *BI) {
   switch (Builtin.ID) {
   default: break;
 
+  case BuiltinValueKind::SUCheckedConversion:
+  case BuiltinValueKind::USCheckedConversion: {
+    OperandValueArrayRef Args = BI->getArguments();
+    const SILValue &Op = Args[0];
+    if (auto signBit = computeSignBit(Op))
+      if (!signBit.getValue())
+        return Op;
+    SILValue Result;
+    // CheckedConversion(ExtOrBitCast(x)) -> x
+    if (match(BI, m_CheckedConversion(m_ExtOrBitCast(m_SILValue(Result)))))
+      if (Result->getType() == BI->getType().getTupleElementType(0)) {
+        assert (!computeSignBit(Result).getValue() && "Sign bit should be 0");
+        return Result;
+      }
+    }
+    break;
+
   case BuiltinValueKind::UToSCheckedTrunc:
   case BuiltinValueKind::UToUCheckedTrunc:
   case BuiltinValueKind::SToUCheckedTrunc:

lib/SILOptimizer/Analysis/ValueTracking.cpp

@@ -296,6 +296,25 @@ Optional<bool> swift::computeSignBit(SILValue V) {
         continue;
       }
 
+      // Source and target type sizes are the same.
+      // S->U conversion can only succeed if
+      // the sign bit of its operand is 0, i.e. it is >= 0.
+      // The sign bit of a result is 0 only if the sign
+      // bit of a source operand is 0.
+      case BuiltinValueKind::SUCheckedConversion:
+        Value = BI->getArguments()[0];
+        continue;
+
+      // Source and target type sizes are the same.
+      // U->S conversion can only succeed if
+      // the top bit of its operand is 0, i.e.
+      // it is representable as a signed integer >=0.
+      // The sign bit of a result is 0 only if the sign
+      // bit of a source operand is 0.
+      case BuiltinValueKind::USCheckedConversion:
+        Value = BI->getArguments()[0];
+        continue;
+
       // Sign bit of the operand is promoted.
       case BuiltinValueKind::SExt:
         Value = BI->getArguments()[0];

lib/SILOptimizer/Transforms/AccessEnforcementReleaseSinking.cpp

@@ -122,6 +122,8 @@ static bool isBarrier(SILInstruction *inst) {
     case BuiltinValueKind::SToUCheckedTrunc:
     case BuiltinValueKind::SToSCheckedTrunc:
     case BuiltinValueKind::UToUCheckedTrunc:
+    case BuiltinValueKind::SUCheckedConversion:
+    case BuiltinValueKind::USCheckedConversion:
     case BuiltinValueKind::IntToFPWithOverflow:
     case BuiltinValueKind::ZeroInitializer:
     case BuiltinValueKind::Once:

lib/SILOptimizer/Utils/ConstExpr.cpp

@@ -210,6 +210,8 @@ ConstExprFunctionState::computeConstantValueBuiltin(BuiltinInst *inst) {
     if (!operand.isConstant())
       return operand;
 
+    // TODO: SUCheckedConversion/USCheckedConversion
+
     // Implement support for s_to_s_checked_trunc_Int2048_Int64 and other
     // checking integer truncates.  These produce a tuple of the result value
     // and an overflow bit.

lib/SILOptimizer/Utils/ConstantFolding.cpp

@@ -674,7 +674,9 @@ constantFoldAndCheckIntegerConversions(BuiltinInst *BI,
   assert(Builtin.ID == BuiltinValueKind::SToSCheckedTrunc ||
          Builtin.ID == BuiltinValueKind::UToUCheckedTrunc ||
          Builtin.ID == BuiltinValueKind::SToUCheckedTrunc ||
-         Builtin.ID == BuiltinValueKind::UToSCheckedTrunc);
+         Builtin.ID == BuiltinValueKind::UToSCheckedTrunc ||
+         Builtin.ID == BuiltinValueKind::SUCheckedConversion ||
+         Builtin.ID == BuiltinValueKind::USCheckedConversion);
 
   // Check if we are converting a constant integer.
   OperandValueArrayRef Args = BI->getArguments();
@@ -686,9 +688,11 @@ constantFoldAndCheckIntegerConversions(BuiltinInst *BI,
   auto SrcBitWidth = SrcVal.getBitWidth();
 
   bool DstTySigned = (Builtin.ID == BuiltinValueKind::SToSCheckedTrunc ||
-                      Builtin.ID == BuiltinValueKind::UToSCheckedTrunc);
+                      Builtin.ID == BuiltinValueKind::UToSCheckedTrunc ||
+                      Builtin.ID == BuiltinValueKind::USCheckedConversion);
   bool SrcTySigned = (Builtin.ID == BuiltinValueKind::SToSCheckedTrunc ||
-                      Builtin.ID == BuiltinValueKind::SToUCheckedTrunc);
+                      Builtin.ID == BuiltinValueKind::SToUCheckedTrunc ||
+                      Builtin.ID == BuiltinValueKind::SUCheckedConversion);
 
   // Get source type and bit width.
   auto SrcTy = Builtin.Types[0]->castTo<AnyBuiltinIntegerType>();
@@ -701,33 +705,44 @@ constantFoldAndCheckIntegerConversions(BuiltinInst *BI,
   bool OverflowError;
   Type DstTy;
 
-  assert(Builtin.Types.size() == 2);
-  DstTy = Builtin.Types[1];
-  uint32_t DstBitWidth =
-    DstTy->castTo<BuiltinIntegerType>()->getGreatestWidth();
-
-  assert((DstBitWidth < SrcBitWidth || !SrcTy->getWidth().isFixedWidth()) &&
-         "preconditions on builtin trunc operations should prevent"
-         "fixed-width truncations that actually extend");
-
-  // The only way a true extension can overflow is if the value is
-  // negative and the result is unsigned.
-  if (DstBitWidth > SrcBitWidth) {
-    OverflowError = (SrcTySigned && !DstTySigned && SrcVal.isNegative());
-    Result = (SrcTySigned ? SrcVal.sext(DstBitWidth)
-                          : SrcVal.zext(DstBitWidth));
-
-  // A same-width change can overflow if the top bit disagrees.
-  } else if (DstBitWidth == SrcBitWidth) {
-    OverflowError = (SrcTySigned != DstTySigned && SrcVal.isNegative());
+  // Process conversions signed <-> unsigned for same size integers.
+  if (Builtin.ID == BuiltinValueKind::SUCheckedConversion ||
+      Builtin.ID == BuiltinValueKind::USCheckedConversion) {
+    DstTy = SrcTy;
     Result = SrcVal;
+    // Report an error if the sign bit is set.
+    OverflowError = SrcVal.isNegative();
 
-  // A truncation can overflow if the value changes.
+  // Process the checked truncations.
   } else {
-    Result = SrcVal.trunc(DstBitWidth);
-    APInt Ext = (DstTySigned ? Result.sext(SrcBitWidth)
-                             : Result.zext(SrcBitWidth));
-    OverflowError = (SrcVal != Ext);
+    assert(Builtin.Types.size() == 2);
+    DstTy = Builtin.Types[1];
+    uint32_t DstBitWidth =
+      DstTy->castTo<BuiltinIntegerType>()->getGreatestWidth();
+
+    assert((DstBitWidth < SrcBitWidth || !SrcTy->getWidth().isFixedWidth()) &&
+           "preconditions on builtin trunc operations should prevent"
+           "fixed-width truncations that actually extend");
+
+    // The only way a true extension can overflow is if the value is
+    // negative and the result is unsigned.
+    if (DstBitWidth > SrcBitWidth) {
+      OverflowError = (SrcTySigned && !DstTySigned && SrcVal.isNegative());
+      Result = (SrcTySigned ? SrcVal.sext(DstBitWidth)
+                            : SrcVal.zext(DstBitWidth));
+
+    // A same-width change can overflow if the top bit disagrees.
+    } else if (DstBitWidth == SrcBitWidth) {
+      OverflowError = (SrcTySigned != DstTySigned && SrcVal.isNegative());
+      Result = SrcVal;
+
+    // A truncation can overflow if the value changes.
+    } else {
+      Result = SrcVal.trunc(DstBitWidth);
+      APInt Ext = (DstTySigned ? Result.sext(SrcBitWidth)
+                               : Result.zext(SrcBitWidth));
+      OverflowError = (SrcVal != Ext);
+    }
   }
 
   // Check for overflow.
@@ -804,19 +819,25 @@ constantFoldAndCheckIntegerConversions(BuiltinInst *BI,
                  DstTySigned, DstTy, SrcAsString);
       }
     } else {
-      // Try to print user-visible types if they are available.
-      if (!UserSrcTy.isNull()) {
+      if (Builtin.ID == BuiltinValueKind::SUCheckedConversion) {
         diagnose(M.getASTContext(), Loc.getSourceLoc(),
-                 diag::integer_conversion_overflow,
-                 UserSrcTy, UserDstTy);
-
-      // Otherwise, print the Builtin Types.
+                 diag::integer_conversion_sign_error,
+                 UserDstTy.isNull() ? DstTy : UserDstTy);
       } else {
-        // Since builtin types are sign-agnostic, print the signedness
-        // separately.
-        diagnose(M.getASTContext(), Loc.getSourceLoc(),
-                 diag::integer_conversion_overflow_builtin_types,
-                 SrcTySigned, SrcTy, DstTySigned, DstTy);
+        // Try to print user-visible types if they are available.
+        if (!UserSrcTy.isNull()) {
+          diagnose(M.getASTContext(), Loc.getSourceLoc(),
+                   diag::integer_conversion_overflow,
+                   UserSrcTy, UserDstTy);
+
+        // Otherwise, print the Builtin Types.
+        } else {
+          // Since builtin types are sign-agnostic, print the signedness
+          // separately.
+          diagnose(M.getASTContext(), Loc.getSourceLoc(),
+                   diag::integer_conversion_overflow_builtin_types,
+                   SrcTySigned, SrcTy, DstTySigned, DstTy);
+        }
       }
     }
 
@@ -1199,7 +1220,9 @@ case BuiltinValueKind::id:
   case BuiltinValueKind::SToSCheckedTrunc:
   case BuiltinValueKind::UToUCheckedTrunc:
   case BuiltinValueKind::SToUCheckedTrunc:
-  case BuiltinValueKind::UToSCheckedTrunc: {
+  case BuiltinValueKind::UToSCheckedTrunc:
+  case BuiltinValueKind::SUCheckedConversion:
+  case BuiltinValueKind::USCheckedConversion: {
     return constantFoldAndCheckIntegerConversions(BI, Builtin, ResultsInError);
   }