Strip IR after front-end steps are done (#1092)

* Strip IR after front-end steps are done

The main feature of this change is to unconditonally strip out the `IRHighLevelDeclDecoration`s in an IR module once the "mandatory" IR passes in the front end have run. This ensures that later IR passes (e.g., code emission) *cannot* rely on AST-level information to get their job done.

Since I was already writing a pass to remove some instructions at the end of the front-end passes, I went ahead and also made the `-obfuscate` flag apply to the front-end IR generation by causing it to strip `IRNameHintDecoration`s while it is doing the other stripping. With this, the main identifying information left in IR modules (other than semantics and entry-point names) is mangled name strings for imported/exported symbols.

A few other things got changes along the way:

* Removed the `.expected` file for one of the tests, where that file seemingly shouldn't have been checked in at all.

* Updated the signature of the DCE pass both so that it doesn't require a back-end compile request (it wasn't using it anyway), and so that it takes some options to decide whether to keep symbols marked `[export(...)]` alive (the front-end wants to keep these, while back-end passes currently need to be able to eliminate them).

* Moved the `obfuscateCode` flag from the back-end compile request to the base class shared between front- and back-end requests, and updated the options and repro logic to set both as needed. An obvious improvement in the future would be to have the front- and back-end requests share these settings by referencing a single common object in the end-to-end case, rather than each having their own copy.

* Removed logic that was keeping layout instructions alive in DCE, even if they weren't used. This seems to have been a vestige of an intermediate step between AST and IR layout.

* fixup: add the new files

1 files changed, 0 insertions, 55 deletions

diff --git a/tests/bugs/texture2d-ms.hlsl.expected b/tests/bugs/texture2d-ms.hlsl.expected
deleted file mode 100644
index 2202bbbec..000000000
--- a/tests/bugs/texture2d-ms.hlsl.expected
+++ /dev/null
@@ -1,55 +0,0 @@
-result code = 0
-standard error = {
-}
-standard output = {
-// Module Version 10000
-// Generated by (magic number): 80007
-// Id's are bound by 30
-
-                              Capability Shader
-               1:             ExtInstImport  "GLSL.std.450"
-                              MemoryModel Logical GLSL450
-                              EntryPoint GLCompute 4  "main" 17
-                              ExecutionMode 4 LocalSize 4 4 1
-                              Source GLSL 450
-                              SourceExtension  "GL_EXT_samplerless_texture_functions"
-                              SourceExtension  "GL_GOOGLE_cpp_style_line_directive"
-                              Name 4  "main"
-                              Name 9  "_S1"
-                              Name 12  "tex_0"
-                              Name 17  "gl_WorkGroupID"
-                              Decorate 12(tex_0) DescriptorSet 0
-                              Decorate 12(tex_0) Binding 0
-                              Decorate 17(gl_WorkGroupID) BuiltIn WorkgroupId
-                              Decorate 29 BuiltIn WorkgroupSize
-               2:             TypeVoid
-               3:             TypeFunction 2
-               6:             TypeFloat 32
-               7:             TypeVector 6(float) 4
-               8:             TypePointer Function 7(fvec4)
-              10:             TypeImage 6(float) 2D multi-sampled sampled format:Unknown
-              11:             TypePointer UniformConstant 10
-       12(tex_0):     11(ptr) Variable UniformConstant
-              14:             TypeInt 32 0
-              15:             TypeVector 14(int) 3
-              16:             TypePointer Input 15(ivec3)
-17(gl_WorkGroupID):     16(ptr) Variable Input
-              18:             TypeVector 14(int) 2
-              21:             TypeInt 32 1
-              22:             TypeVector 21(int) 2
-              24:     21(int) Constant 0
-              27:     14(int) Constant 4
-              28:     14(int) Constant 1
-              29:   15(ivec3) ConstantComposite 27 27 28
-         4(main):           2 Function None 3
-               5:             Label
-          9(_S1):      8(ptr) Variable Function
-              13:          10 Load 12(tex_0)
-              19:   15(ivec3) Load 17(gl_WorkGroupID)
-              20:   18(ivec2) VectorShuffle 19 19 0 1
-              23:   22(ivec2) Bitcast 20
-              25:    7(fvec4) ImageFetch 13 23 Sample 24
-                              Store 9(_S1) 25
-                              Return
-                              FunctionEnd
-}