SPV 1.4: Use OpSelect for trivial typed non-scalar/vector expressions.

Test/spv.1.4.OpSelect.frag

@@ -0,0 +1,37 @@
+#version 450
+
+struct S1 {
+    float a;
+    int b;
+};
+
+layout(location = 0) flat in S1 in1;
+layout(location = 2) flat in S1 in2;
+layout(location = 4) flat in int cond;
+
+layout(location = 0) out float outv;
+
+void fun1(){}
+void fun2(){}
+
+void main()
+{
+    // glslang will only make OpSelect for very trivial looking expressions
+
+    float f1 = 1.0;
+    float f2 = 2.0;
+    outv = cond < 8 ? f1 : f2;           // in all versions
+
+    ivec4 iv1 = ivec4(f1);
+    ivec4 iv2 = ivec4(f2);
+    outv *= (cond > 0 ? iv1 : iv2).z;     // in all versions, but in 1.4 as scalar condition, not smeared ala mix()
+
+    mat3 m1 = mat3(1.0);
+    mat3 m2 = mat3(2.0);
+    outv *= (cond < 20 ? m1 : m2)[2][1];  // in 1.4, but not before
+
+    S1 fv = cond > 5 ? in1 : in2;         // in 1.4, but not before
+    outv *= fv.a;
+
+    cond > 0 ? fun1() : fun2();           // not allowed by any version
+}