Swift SIL: fix KeyPathInst.visitReferencedFunctions

It crashed for keypath instructions with zero components.

Author: eeckstein

SwiftCompilerSources/Sources/SIL/Instruction.swift

@@ -480,9 +480,8 @@ final public class RefTailAddrInst : SingleValueInstruction, UnaryInstruction {}
 final public class KeyPathInst : SingleValueInstruction {
   public override func visitReferencedFunctions(_ cl: (Function) -> ()) {
     var results = KeyPathFunctionResults()
-    var componentIdx = 0
-    repeat {
-      componentIdx = KeyPathInst_getReferencedFunctions(bridged, componentIdx, &results)
+    for componentIdx in 0..<KeyPathInst_getNumComponents(bridged) {
+      KeyPathInst_getReferencedFunctions(bridged, componentIdx, &results)
       let numFuncs = results.numFunctions
       withUnsafePointer(to: &results) {
         $0.withMemoryRebound(to: BridgedFunction.self, capacity: numFuncs) {
@@ -492,7 +491,7 @@ final public class KeyPathInst : SingleValueInstruction {
           }
         }
       }
-    } while componentIdx >= 0
+    }
   }
 }
 

include/swift/SIL/SILBridging.h

@@ -399,7 +399,8 @@ struct KeyPathFunctionResults {
   BridgedFunction functions[maxFunctions];
   SwiftInt numFunctions;
 };
-SwiftInt KeyPathInst_getReferencedFunctions(BridgedInstruction kpi, SwiftInt componentIdx,
+SwiftInt KeyPathInst_getNumComponents(BridgedInstruction kpi);
+void KeyPathInst_getReferencedFunctions(BridgedInstruction kpi, SwiftInt componentIdx,
                                             KeyPathFunctionResults * _Nonnull results);
 
 BridgedSubstitutionMap ApplySite_getSubstitutionMap(BridgedInstruction inst);

lib/SIL/Utils/SILBridging.cpp

@@ -886,7 +886,14 @@ SwiftInt CondBranchInst_getNumTrueArgs(BridgedInstruction cbr) {
   return castToInst<CondBranchInst>(cbr)->getNumTrueArgs();
 }
 
-SwiftInt KeyPathInst_getReferencedFunctions(BridgedInstruction kpi, SwiftInt componentIdx,
+SwiftInt KeyPathInst_getNumComponents(BridgedInstruction kpi) {
+  if (KeyPathPattern *pattern = castToInst<KeyPathInst>(kpi)->getPattern()) {
+    return (SwiftInt)pattern->getComponents().size();
+  }
+  return 0;
+}
+
+void KeyPathInst_getReferencedFunctions(BridgedInstruction kpi, SwiftInt componentIdx,
                                             KeyPathFunctionResults * _Nonnull results) {
   KeyPathPattern *pattern = castToInst<KeyPathInst>(kpi)->getPattern();
   const KeyPathPatternComponent &comp = pattern->getComponents()[componentIdx];
@@ -896,9 +903,6 @@ SwiftInt KeyPathInst_getReferencedFunctions(BridgedInstruction kpi, SwiftInt com
       assert(results->numFunctions < KeyPathFunctionResults::maxFunctions);
       results->functions[results->numFunctions++] = {func};
     }, [](SILDeclRef) {});
-
-  ++componentIdx;
-  return componentIdx < (int)pattern->getComponents().size() ? componentIdx : -1;
 }
 
 BridgedSubstitutionMap ApplySite_getSubstitutionMap(BridgedInstruction inst) {