Test for and prevent any dead-code elimination, as all code is needed in the AST for static-use analysis.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@23163 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/dce.frag

@@ -0,0 +1,56 @@
+#version 400
+
+const bool flag = false;
+
+int c = 0;
+
+void bar()
+{
+    if (flag)
+        ++c;  // should still show up in AST
+    else
+        ++c;
+
+    flag ? ++c : ++c;  // both should still show up in AST
+
+    switch (c) {
+    case 1:
+        ++c;
+        break;
+        ++c;  // should still show up in AST
+    case 2:
+        break;
+        ++c;  // should still show up in AST
+    default:
+        break;
+    }
+
+    for (int i = 0; i < 0; ++i)
+        ++c;  // should still show up in AST
+
+    for (int i = 0; i < 10; ++i) {
+        if (c < 3) {
+            break; 
+            ++c;    // should still show up in AST
+        } else {
+            continue;
+            ++c;    // should still show up in AST
+        }
+    }
+
+    return;
+
+    ++c;      // should still show up in AST
+}
+
+int foo()     // not called, but should still show up in AST
+{
+    if (c > 4) {
+        return 4;
+        ++c;   // should still show up in AST
+    }
+
+    return 5;
+
+    ++c;       // should still show up in AST
+}