Implement GL_EXT_demote_to_helper_invocation

Test/baseResults/spv.conditionalDemote.frag.out

@@ -0,0 +1,70 @@
+spv.conditionalDemote.frag
+Validation failed
+// Module Version 10000
+// Generated by (magic number): 80007
+// Id's are bound by 38
+
+                              Capability Shader
+                              Capability Bad
+                              Extension  "SPV_EXT_demote_to_helper_invocation"
+               1:             ExtInstImport  "GLSL.std.450"
+                              MemoryModel Logical GLSL450
+                              EntryPoint Fragment 4  "main" 17 36
+                              ExecutionMode 4 OriginUpperLeft
+                              Source GLSL 460
+                              SourceExtension  "GL_EXT_demote_to_helper_invocation"
+                              Name 4  "main"
+                              Name 9  "v"
+                              Name 13  "tex"
+                              Name 17  "coord"
+                              Name 33  "x"
+                              Name 36  "o"
+                              Decorate 13(tex) DescriptorSet 0
+                              Decorate 13(tex) Binding 0
+                              Decorate 17(coord) Location 0
+                              Decorate 36(o) Location 0
+               2:             TypeVoid
+               3:             TypeFunction 2
+               6:             TypeFloat 32
+               7:             TypeVector 6(float) 4
+               8:             TypePointer Function 7(fvec4)
+              10:             TypeImage 6(float) 2D sampled format:Unknown
+              11:             TypeSampledImage 10
+              12:             TypePointer UniformConstant 11
+         13(tex):     12(ptr) Variable UniformConstant
+              15:             TypeVector 6(float) 2
+              16:             TypePointer Input 15(fvec2)
+       17(coord):     16(ptr) Variable Input
+              21:    6(float) Constant 1036831949
+              22:    6(float) Constant 1045220557
+              23:    6(float) Constant 1050253722
+              24:    6(float) Constant 1053609165
+              25:    7(fvec4) ConstantComposite 21 22 23 24
+              26:             TypeBool
+              27:             TypeVector 26(bool) 4
+              32:             TypePointer Function 26(bool)
+              35:             TypePointer Output 7(fvec4)
+           36(o):     35(ptr) Variable Output
+         4(main):           2 Function None 3
+               5:             Label
+            9(v):      8(ptr) Variable Function
+           33(x):     32(ptr) Variable Function
+              14:          11 Load 13(tex)
+              18:   15(fvec2) Load 17(coord)
+              19:    7(fvec4) ImageSampleImplicitLod 14 18
+                              Store 9(v) 19
+              20:    7(fvec4) Load 9(v)
+              28:   27(bvec4) FOrdEqual 20 25
+              29:    26(bool) All 28
+                              SelectionMerge 31 None
+                              BranchConditional 29 30 31
+              30:               Label
+                                DemoteToHelperInvocationEXT
+                                Branch 31
+              31:             Label
+              34:    26(bool) IsHelperInvocationEXT
+                              Store 33(x) 34
+              37:    7(fvec4) Load 9(v)
+                              Store 36(o) 37
+                              Return
+                              FunctionEnd

Test/baseResults/spv.demoteDisabled.frag.out

@@ -0,0 +1,6 @@
+spv.demoteDisabled.frag
+ERROR: 0:9: 'demote' : undeclared identifier 
+ERROR: 1 compilation errors.  No code generated.
+
+
+SPIR-V is not generated for failed compile or link