Fix HLSL for switch statements that don't end in a branch

src/compiler/translator/OutputHLSL.cpp

@@ -2137,9 +2137,12 @@ bool OutputHLSL::visitSwitch(Visit visit, TIntermSwitch *node)
 
     if (node->getStatementList())
     {
-        node->setStatementList(RemoveSwitchFallThrough(node->getStatementList()));
+        if (visit == PreVisit)
+        {
+            node->setStatementList(RemoveSwitchFallThrough(node->getStatementList()));
+        }
         outputTriplet(out, visit, "switch (", ") ", "");
-        // The curly braces get written when visiting the statementList aggregate
+        // The curly braces get written when visiting the statementList block.
     }
     else
     {

src/compiler/translator/RemoveSwitchFallThrough.cpp

@@ -56,14 +56,16 @@ TIntermBlock *RemoveSwitchFallThroughTraverser::removeFallThrough(TIntermBlock *
     RemoveSwitchFallThroughTraverser rm(statementList);
     ASSERT(statementList);
     statementList->traverse(&rm);
-    bool lastStatementWasBreak = rm.mLastStatementWasBreak;
-    rm.mLastStatementWasBreak  = true;
-    rm.handlePreviousCase();
-    if (!lastStatementWasBreak)
+    ASSERT(rm.mPreviousCase || statementList->getSequence()->empty());
+    if (!rm.mLastStatementWasBreak && rm.mPreviousCase)
     {
+        // Make sure that there's a branch at the end of the final case inside the switch statement.
+        // This also ensures that any cases that fall through to the final case will get the break.
         TIntermBranch *finalBreak = new TIntermBranch(EOpBreak, nullptr);
-        rm.mStatementListOut->getSequence()->push_back(finalBreak);
+        rm.mPreviousCase->getSequence()->push_back(finalBreak);
+        rm.mLastStatementWasBreak = true;
     }
+    rm.handlePreviousCase();
     return rm.mStatementListOut;
 }
 

src/tests/gl_tests/GLSLTest.cpp

@@ -3499,6 +3499,45 @@ TEST_P(GLSLTest_ES3, DifferentStatementsInsideSwitch)
     ANGLE_GL_PROGRAM(program, mSimpleVSSource, fragmentShader);
 }
 
+// Test that switch fall-through works correctly.
+// This is a regression test for http://anglebug.com/2178
+TEST_P(GLSLTest_ES3, SwitchFallThroughCodeDuplication)
+{
+    const std::string &fragmentShader =
+        R"(#version 300 es
+
+        precision highp float;
+
+        out vec4 my_FragColor;
+
+        uniform int u_zero;
+
+        void main()
+        {
+            int i = 0;
+            // switch should fall through both cases.
+            switch(u_zero)
+            {
+                case 0:
+                    i += 1;
+                case 1:
+                    i += 2;
+            }
+            if (i == 3)
+            {
+                my_FragColor = vec4(0, 1, 0, 1);
+            }
+            else
+            {
+                my_FragColor = vec4(1, 0, 0, 1);
+            }
+        })";
+
+    ANGLE_GL_PROGRAM(program, mSimpleVSSource, fragmentShader);
+    drawQuad(program.get(), "inputAttribute", 0.5f);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
 // Use this to select which configurations (e.g. which renderer, which GLES major version) these tests should be run against.
 ANGLE_INSTANTIATE_TEST(GLSLTest,
                        ES2_D3D9(),