Merge pull request #63129 from eeckstein/fix-walk-utils

WalkUtils: fix a crash when visiting mismatching types

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/Utilities/WalkUtils.swift

@@ -569,6 +569,11 @@ extension ValueUseDefWalker {
     switch def {
     case let str as StructInst:
       if let (index, path) = path.pop(kind: .structField) {
+        if index >= str.operands.count {
+          // This can happen if there is a type mismatch, e.g. two different concrete types of an existential
+          // are visited for the same path.
+          return unmatchedPath(value: str, path: path)
+        }
         return walkUp(value: str.operands[index].value, path: path)
       } else if path.popIfMatches(.anyValueFields, index: nil) != nil {
         return walkUpAllOperands(of: str, path: path)
@@ -577,6 +582,11 @@ extension ValueUseDefWalker {
       }
     case let t as TupleInst:
       if let (index, path) = path.pop(kind: .tupleField) {
+        if index >= t.operands.count {
+          // This can happen if there is a type mismatch, e.g. two different concrete types of an existential
+          // are visited for the same path.
+          return unmatchedPath(value: t, path: path)
+        }
         return walkUp(value: t.operands[index].value, path: path)
       } else if path.popIfMatches(.anyValueFields, index: nil) != nil {
         return walkUpAllOperands(of: t, path: path)

test/SILOptimizer/escape_info.sil

@@ -41,7 +41,14 @@ final class F {
   @_hasStorage var y: Y
 }
 
-struct TwoF {
+protocol P {
+}
+
+struct OneF : P {
+  @_hasStorage var a: F
+}
+
+struct TwoF : P {
   @_hasStorage var a: F
   @_hasStorage var b: F
 }
@@ -1343,3 +1350,30 @@ bb0:
   return %13 : $()
 }
 
+// CHECK-LABEL: Escape information for test_mismatching_existential_types:
+// CHECK:  -    :   %1 = alloc_ref $Y
+// CHECK: End function test_mismatching_existential_types
+sil @test_mismatching_existential_types : $@convention(thin) (@guaranteed F) -> () {
+bb0(%0 : $F):
+  %1 = alloc_ref $Y
+
+  %2 = alloc_stack $any P
+
+  %3 = init_existential_addr %2 : $*any P, $OneF
+  %4 = struct $OneF (%0 : $F)
+  store %4 to %3 : $*OneF
+
+  // Strictly speaking it's illegal to re-initialize an existential with a different concrete type.
+  // But for this test this doesn't matter.
+  %6 = init_existential_addr %2 : $*any P, $TwoF
+  %7 = struct_element_addr %6 : $*TwoF, #TwoF.b
+  %8 = load %7 : $*F
+
+  %9 = ref_element_addr %8 : $F, #F.y
+  store %1 to %9 : $*Y
+
+  dealloc_stack %2 : $*any P
+  %r = tuple()
+  return %r : $()
+}
+