IRGen: gatherbits - extend the bits before we shift left

SR-9335
rdar://46264497

Author: aschwaighofer

lib/IRGen/EnumPayload.cpp

@@ -719,9 +719,10 @@ llvm::Value *irgen::emitGatherSpareBits(IRGenFunction &IGF,
     llvm::Value *newBits;
     if (u > usedBits)
       newBits = IGF.Builder.CreateLShr(spareBits, u - usedBits);
-    else if (u < usedBits)
-      newBits = IGF.Builder.CreateShl(spareBits, usedBits - u);
-    else
+    else if (u < usedBits) {
+      newBits = IGF.Builder.CreateZExtOrTrunc(spareBits, destTy);
+      newBits = IGF.Builder.CreateShl(newBits, usedBits - u);
+    } else
       newBits = spareBits;
     newBits = IGF.Builder.CreateZExtOrTrunc(newBits, destTy);
 

test/IRGen/multi_payload_shifting.swift

@@ -0,0 +1,32 @@
+// RUN: %target-swift-frontend -enable-objc-interop -assume-parsing-unqualified-ownership-sil -primary-file %s -emit-ir | %FileCheck %s
+
+// REQUIRES: CPU=x86_64
+
+class Tag {}
+
+struct Scalar {
+  var str = ""
+  var x = Tag()
+  var style: BinaryChoice  = .zero
+  enum BinaryChoice: UInt32 {
+    case zero = 0
+    case one
+  }
+}
+
+public struct Sequence {
+  var tag: Tag = Tag()
+  var tag2: Tag = Tag()
+}
+
+enum Node {
+  case scalar(Scalar)
+  case sequence(Sequence)
+}
+
+// CHECK: define internal i32 @"$s22multi_payload_shifting4NodeOwet"(%swift.opaque* noalias %value, i32 %numEmptyCases, %swift.type* %Node) #9 {
+// CHECK:  [[ADDR:%.*]] = getelementptr inbounds { i64, i64, i64, i8 }, { i64, i64, i64, i8 }* {{.*}}, i32 0, i32 3
+// CHECK:  [[BYTE:%.*]] = load i8, i8* [[ADDR]]
+// Make sure we zext before we shift.
+// CHECK:  [[ZEXT:%.*]] = zext i8 [[BYTE]] to i32
+// CHECK:  shl i32 [[ZEXT]], 10

test/Interpreter/multi_payload_shifting.swift

@@ -0,0 +1,53 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-build-swift -o %t/a.out %s
+// RUN: %target-run %t/a.out 2>&1
+
+// REQUIRES: executable_test
+
+import Swift
+import StdlibUnittest
+
+class Tag {}
+
+struct Scalar {
+  var str = ""
+  var x = Tag()
+  var style: BinaryChoice  = .zero
+  enum BinaryChoice: UInt32 {
+    case zero = 0
+    case one
+  }
+}
+
+public struct Sequence {
+  var tag: Tag = Tag()
+  var tag2: Tag = Tag()
+}
+
+enum Node {
+  case scalar(Scalar)
+  case sequence(Sequence)
+}
+
+func createOptionalNodeNil<T>(_ t: T) -> T? {
+  return nil
+}
+
+func isNil<T>(_ t: T?) -> Bool {
+  return t == nil
+}
+
+var tests = TestSuite("extra inhabitants shifts")
+
+
+tests.test("test-shift-fix") {
+  let opt = createOptionalNodeNil(Node.scalar(Scalar()))
+  var res = false
+  if isNil(opt) {
+    res = true
+  }
+  expectEqual(true, res)
+}
+
+runAllTests()