Handle OpUnreachable in code-gen.

Forgot to add it to emit_block_chain. It should just be a noop.

reference/opt/shaders/asm/frag/unreachable.asm.frag

@@ -0,0 +1,28 @@
+#version 450
+
+layout(location = 0) flat in int counter;
+layout(location = 0) out vec4 FragColor;
+
+vec4 _21;
+
+void main()
+{
+    vec4 _15;
+    vec4 _17;
+    vec4 _33;
+    do
+    {
+        if (counter == 10)
+        {
+            _33 = vec4(10.0);
+            break;
+        }
+        else
+        {
+            _33 = vec4(30.0);
+            break;
+        }
+    } while (false);
+    FragColor = _33;
+}
+

reference/shaders/asm/frag/unreachable.asm.frag

@@ -0,0 +1,30 @@
+#version 450
+
+layout(location = 0) flat in int counter;
+layout(location = 0) out vec4 FragColor;
+
+vec4 _21;
+
+void main()
+{
+    vec4 _15;
+    vec4 _17;
+    vec4 _24;
+    vec4 _33;
+    _24 = _21;
+    for (;;)
+    {
+        if (counter == 10)
+        {
+            _33 = vec4(10.0);
+            break;
+        }
+        else
+        {
+            _33 = vec4(30.0);
+            break;
+        }
+    }
+    FragColor = _33;
+}
+

shaders/asm/frag/unreachable.asm.frag

@@ -0,0 +1,61 @@
+; SPIR-V
+; Version: 1.0
+; Generator: Khronos Glslang Reference Front End; 3
+; Bound: 47
+; Schema: 0
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Fragment %main "main" %counter %FragColor
+               OpExecutionMode %main OriginUpperLeft
+               OpSource GLSL 450
+               OpName %main "main"
+               OpName %counter "counter"
+               OpName %FragColor "FragColor"
+               OpDecorate %counter Flat
+               OpDecorate %counter Location 0
+               OpDecorate %FragColor Location 0
+       %void = OpTypeVoid
+          %3 = OpTypeFunction %void
+      %float = OpTypeFloat 32
+    %v4float = OpTypeVector %float 4
+          %8 = OpTypeFunction %v4float
+        %int = OpTypeInt 32 1
+%_ptr_Input_int = OpTypePointer Input %int
+    %counter = OpVariable %_ptr_Input_int Input
+     %int_10 = OpConstant %int 10
+       %bool = OpTypeBool
+   %float_10 = OpConstant %float 10
+         %21 = OpConstantComposite %v4float %float_10 %float_10 %float_10 %float_10
+   %float_30 = OpConstant %float 30
+         %25 = OpConstantComposite %v4float %float_30 %float_30 %float_30 %float_30
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+  %FragColor = OpVariable %_ptr_Output_v4float Output
+%_ptr_Function_v4float = OpTypePointer Function %v4float
+      %false = OpConstantFalse %bool
+         %44 = OpUndef %v4float
+       %main = OpFunction %void None %3
+          %5 = OpLabel
+               OpBranch %33
+         %33 = OpLabel
+         %45 = OpPhi %v4float %44 %5 %44 %35
+               OpLoopMerge %34 %35 None
+               OpBranch %36
+         %36 = OpLabel
+         %37 = OpLoad %int %counter
+         %38 = OpIEqual %bool %37 %int_10
+               OpSelectionMerge %39 None
+               OpBranchConditional %38 %40 %41
+         %40 = OpLabel
+               OpBranch %34
+         %41 = OpLabel
+               OpBranch %34
+         %39 = OpLabel
+               OpUnreachable
+         %35 = OpLabel
+               OpBranchConditional %false %33 %34
+         %34 = OpLabel
+         %46 = OpPhi %v4float %21 %40 %25 %41 %44 %35
+               OpStore %FragColor %46
+               OpReturn
+               OpFunctionEnd

spirv_glsl.cpp

@@ -8357,6 +8357,10 @@ void CompilerGLSL::emit_block_chain(SPIRBlock &block)
 		statement(backend.discard_literal, ";");
 		break;
 
+	case SPIRBlock::Unreachable:
+		emit_next_block = false;
+		break;
+
 	default:
 		SPIRV_CROSS_THROW("Unimplemented block terminator.");
 	}