diff --git a/src/main/java/com/android/tools/r8/Version.java b/src/main/java/com/android/tools/r8/Version.java
index 0ba40b3..fb3b067 100644
--- a/src/main/java/com/android/tools/r8/Version.java
+++ b/src/main/java/com/android/tools/r8/Version.java
@@ -11,7 +11,7 @@
 
   // This field is accessed from release scripts using simple pattern matching.
   // Therefore, changing this field could break our release scripts.
-  public static final String LABEL = "1.2.20-dev";
+  public static final String LABEL = "1.2.21-dev";
 
   private Version() {
   }
diff --git a/src/main/java/com/android/tools/r8/utils/ArchiveResourceProvider.java b/src/main/java/com/android/tools/r8/utils/ArchiveResourceProvider.java
index 37aa208..499ba47 100644
--- a/src/main/java/com/android/tools/r8/utils/ArchiveResourceProvider.java
+++ b/src/main/java/com/android/tools/r8/utils/ArchiveResourceProvider.java
@@ -54,17 +54,18 @@
       while (entries.hasMoreElements()) {
         ZipEntry entry = entries.nextElement();
         try (InputStream stream = zipFile.getInputStream(entry)) {
-          Path name = Paths.get(entry.getName());
-          Origin entryOrigin = new ArchiveEntryOrigin(entry.getName(), origin);
-          if (archive.matchesFile(name)) {
-            if (isDexFile(name)) {
+          String name = entry.getName();
+          Path path = Paths.get(name);
+          Origin entryOrigin = new ArchiveEntryOrigin(name, origin);
+          if (archive.matchesFile(path)) {
+            if (isDexFile(path)) {
               if (!ignoreDexInArchive) {
                 ProgramResource resource =
                     OneShotByteResource.create(
                         Kind.DEX, entryOrigin, ByteStreams.toByteArray(stream), null);
                 dexResources.add(resource);
               }
-            } else if (isClassFile(name)) {
+            } else if (isClassFile(path)) {
               String descriptor = DescriptorUtils.guessTypeDescriptor(name);
               ProgramResource resource =
                   OneShotByteResource.create(
diff --git a/src/main/java/com/android/tools/r8/utils/DescriptorUtils.java b/src/main/java/com/android/tools/r8/utils/DescriptorUtils.java
index fa045e6..a846ea7 100644
--- a/src/main/java/com/android/tools/r8/utils/DescriptorUtils.java
+++ b/src/main/java/com/android/tools/r8/utils/DescriptorUtils.java
@@ -341,22 +341,35 @@
     }
   }
 
-  // Guess class descriptor from location of the class file.
+  /**
+   * Guess class descriptor from location of the class file on the file system
+   *
+   * @param name Path of the file to convert to the corresponding descriptor
+   * @return java class descriptor
+   */
   public static String guessTypeDescriptor(Path name) {
-    return guessTypeDescriptor(name.toString());
+    String fileName = name.toString();
+    if (File.separatorChar != '/') {
+      fileName = fileName.replace(File.separatorChar, '/');
+    }
+    return guessTypeDescriptor(fileName);
   }
 
-  // Guess class descriptor from location of the class file.
+  /**
+   * Guess class descriptor from location of the class file. This method assumes that the
+   * name uses '/' as the separator. Therefore, this should not be the name of a file
+   * on a file system.
+   *
+   * @param name the location of the class file to convert to descriptor
+   * @return java class descriptor
+   */
   public static String guessTypeDescriptor(String name) {
     assert name != null;
     assert name.endsWith(CLASS_EXTENSION) :
         "Name " + name + " must have " + CLASS_EXTENSION + " suffix";
-    String fileName =
-        File.separatorChar == '/' ? name.toString() :
-            name.toString().replace(File.separatorChar, '/');
-    String descriptor = fileName.substring(0, fileName.length() - CLASS_EXTENSION.length());
+    String descriptor = name.substring(0, name.length() - CLASS_EXTENSION.length());
     if (descriptor.contains(".")) {
-      throw new CompilationError("Unexpected class file name: " + fileName);
+      throw new CompilationError("Unexpected class file name: " + name);
     }
     return 'L' + descriptor + ';';
   }
diff --git a/src/test/java/com/android/tools/r8/AsmTestBase.java b/src/test/java/com/android/tools/r8/AsmTestBase.java
index 9cc2b48..8038c98 100644
--- a/src/test/java/com/android/tools/r8/AsmTestBase.java
+++ b/src/test/java/com/android/tools/r8/AsmTestBase.java
@@ -64,6 +64,10 @@
     Assert.assertEquals(javaResult.stdout, d8Result.stdout);
     Assert.assertEquals(javaResult.stdout, r8Result.stdout);
     Assert.assertEquals(javaResult.stdout, r8ShakenResult.stdout);
+    Assert.assertEquals(0, javaResult.exitCode);
+    Assert.assertEquals(0, d8Result.exitCode);
+    Assert.assertEquals(0, r8Result.exitCode);
+    Assert.assertEquals(0, r8ShakenResult.exitCode);
   }
 
   protected void ensureR8FailsWithCompilationError(String main, byte[]... classes)
diff --git a/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Dump_WithPhi.java b/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Dump_WithPhi.java
index 8a6bdcf..bfb0674 100644
--- a/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Dump_WithPhi.java
+++ b/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Dump_WithPhi.java
@@ -231,21 +231,25 @@
       mv.visitJumpInsn(IFEQ, l7_b1);
       mv.visitLabel(l7_b0);
       mv.visitInsn(ACONST_NULL);
+      // At this point, NULL flows to l7_join.
       mv.visitJumpInsn(GOTO, l7_join);
       mv.visitLabel(l7_b1);
       mv.visitVarInsn(ALOAD, 10);
-      // Swap the new-instance or null, with the byte-array.
+      // At this point, an uninitialized String flows to l7_join.
       mv.visitLabel(l7_join);
+      // At this point, stack contains [staticByteArray, NULL/uninitialized]
       mv.visitInsn(SWAP);
-      // Load the new-instacne and swap again with the byte-array.
+      // At this point, stack contains [NULL/uninitialized, staticByteArray]
       mv.visitVarInsn(ALOAD, 10);
+      // At this point, stack contains [NULL/uninitialized, staticByteArray, uninitialized]
       mv.visitInsn(SWAP);
+      // At this point, stack contains [NULL/uninitialized, uninitialized, staticByteArray]
       mv.visitInsn(ICONST_0);
-      // Invoke special will now always be on the new-instance as receiver.
+      // At this point, stack contains [NULL/uninitialized, uninitialized, staticByteArray, 0]
       mv.visitMethodInsn(INVOKESPECIAL, "java/lang/String", "<init>", "([BI)V", false);
-      // Return will be either new-instance or null.
+      // Just before ARETURN, stack contains [NULL/String].
       // This will force a non-trivial phi of the new-instance on this block, ie, prior to <init>.
-      // This phi must remain.
+      // This phi must remain since it is not trivial.
       mv.visitInsn(ARETURN);
       mv.visitLabel(l8);
       mv.visitVarInsn(ILOAD, 0);
diff --git a/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Utils.java b/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Utils.java
index ff7da8f..ccf6467 100644
--- a/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Utils.java
+++ b/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232Utils.java
@@ -31,13 +31,14 @@
 
   public static void compare(String output, int iterations) {
     String expected = "java.security.SecureRandom";
-    if (output.equals(expected)) {
+    if (expected.equals(output)) {
       return;
     }
     System.out.println(
         "After " + iterations + " iterations, expected \"" +
         expected + "\", but got \"" + output + "\"");
-    System.exit(1);
+    // Exit with code 0 to allow test to use ensureSameOutput().
+    System.exit(0);
   }
 
   public static void compareHash(int a, int b, byte[] c, int iterations) {
@@ -53,6 +54,7 @@
     System.out.println("staticIntB: " + b);
     System.out.print("staticIntByteArray: ");
     printByteArray(c);
-    System.exit(1);
+    // Exit with code 0 to allow test to use ensureSameOutput().
+    System.exit(0);
   }
 }
diff --git a/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232_WithPhi.java b/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232_WithPhi.java
index 3c7c465..3a56004 100644
--- a/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232_WithPhi.java
+++ b/src/test/java/com/android/tools/r8/regress/b78493232/Regress78493232_WithPhi.java
@@ -3,8 +3,15 @@
 // BSD-style license that can be found in the LICENSE file.
 package com.android.tools.r8.regress.b78493232;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
 import com.android.tools.r8.AsmTestBase;
 import com.android.tools.r8.ToolHelper;
+import com.android.tools.r8.ToolHelper.DexVm.Version;
+import com.android.tools.r8.ToolHelper.ProcessResult;
+import com.android.tools.r8.errors.Unreachable;
+import com.android.tools.r8.utils.AndroidApp;
 import org.junit.Test;
 
 // Variant of Regress78493232, but where the new-instance is forced to flow to a non-trivial phi
@@ -15,6 +22,57 @@
   public void test() throws Exception {
     // Run test on JVM and ART(x86) to ensure expected behavior.
     // Running the same test on an ARM JIT causes errors.
+
+    // TODO(b/80118070): Remove this if-statement when fixed.
+    if (ToolHelper.getDexVm().getVersion() != Version.V5_1_1) {
+      AndroidApp app =
+          buildAndroidApp(
+              Regress78493232Dump_WithPhi.dump(),
+              ToolHelper.getClassAsBytes(Regress78493232Utils.class));
+      ProcessResult javaResult =
+          runOnJava(
+              Regress78493232Dump_WithPhi.CLASS_NAME,
+              Regress78493232Dump_WithPhi.dump(),
+              ToolHelper.getClassAsBytes(Regress78493232Utils.class));
+      ProcessResult d8Result =
+          runOnArtRaw(compileWithD8(app), Regress78493232Dump_WithPhi.CLASS_NAME);
+      ProcessResult r8Result =
+          runOnArtRaw(compileWithR8(app), Regress78493232Dump_WithPhi.CLASS_NAME);
+      String proguardConfig =
+          keepMainProguardConfiguration(Regress78493232Dump_WithPhi.CLASS_NAME)
+              + "-dontobfuscate\n";
+      ProcessResult r8ShakenResult =
+          runOnArtRaw(compileWithR8(app, proguardConfig), Regress78493232Dump_WithPhi.CLASS_NAME);
+      assertEquals(
+          "After 0 iterations, expected \"java.security.SecureRandom\", but got \"null\"\n",
+          javaResult.stdout);
+      assertEquals(0, javaResult.exitCode);
+      switch (ToolHelper.getDexVm().getVersion()) {
+        case V4_0_4:
+        case V4_4_4:
+        case V7_0_0:
+        case DEFAULT:
+          assertNotEquals(-1, d8Result.stderr.indexOf("java.lang.VerifyError"));
+          assertNotEquals(-1, r8Result.stderr.indexOf("java.lang.VerifyError"));
+          assertNotEquals(-1, r8ShakenResult.stderr.indexOf("java.lang.VerifyError"));
+          assertEquals(1, d8Result.exitCode);
+          assertEquals(1, r8Result.exitCode);
+          assertEquals(1, r8ShakenResult.exitCode);
+          break;
+        case V6_0_1:
+          assertEquals("Completed successfully after 1000 iterations\n", d8Result.stdout);
+          assertEquals("Completed successfully after 1000 iterations\n", r8Result.stdout);
+          assertEquals("Completed successfully after 1000 iterations\n", r8ShakenResult.stdout);
+          assertEquals(0, d8Result.exitCode);
+          assertEquals(0, r8Result.exitCode);
+          assertEquals(0, r8ShakenResult.exitCode);
+          break;
+        case V5_1_1:
+        default:
+          throw new Unreachable();
+      }
+      return;
+    }
     ensureSameOutput(
         Regress78493232Dump_WithPhi.CLASS_NAME,
         Regress78493232Dump_WithPhi.dump(),
diff --git a/src/test/java/com/android/tools/r8/utils/DescriptorUtilsTest.java b/src/test/java/com/android/tools/r8/utils/DescriptorUtilsTest.java
index 58180e3..7ad9163 100644
--- a/src/test/java/com/android/tools/r8/utils/DescriptorUtilsTest.java
+++ b/src/test/java/com/android/tools/r8/utils/DescriptorUtilsTest.java
@@ -6,7 +6,10 @@
 
 import static org.junit.Assert.assertEquals;
 
+import java.io.File;
 import java.io.IOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import org.junit.Test;
 
 public class DescriptorUtilsTest {
@@ -67,4 +70,16 @@
     assertEquals("java.lang.Object", DescriptorUtils.descriptorToJavaType("Ljava/lang/Object;"));
     assertEquals("a.b.C", DescriptorUtils.descriptorToJavaType("La/b/C;"));
   }
+
+  @Test
+  public void guessClassDescriptor() {
+    String obj = "java/lang/Object.class";
+    assertEquals("Ljava/lang/Object;", DescriptorUtils.guessTypeDescriptor(obj));
+    String objBackslash = "java\\lang\\Object.class";
+    assertEquals("Ljava\\lang\\Object;", DescriptorUtils.guessTypeDescriptor(objBackslash));
+    String objFileSeparatorChar =
+        "java" + File.separatorChar + "lang" + File.separatorChar + "Object.class";
+    assertEquals("Ljava/lang/Object;",
+        DescriptorUtils.guessTypeDescriptor(Paths.get(objFileSeparatorChar)));
+  }
 }