SPV: Support texelFetch() on a textureBuffer (no sampler).

Fixes Vulkan Khronos-internal issue 770.

Test/baseResults/spv.specConstant.vert.out

@@ -13,7 +13,7 @@ Warning, version 400 is not yet complete; most version-specific features are pre
                               Source GLSL 400
                               Name 4  "main"
                               Name 9  "arraySize"
-                              Name 14  "foo(vf4[s1518];"
+                              Name 14  "foo(vf4[s1521];"
                               Name 13  "p"
                               Name 17  "builtin_spec_constant("
                               Name 20  "color"
@@ -104,10 +104,10 @@ Warning, version 400 is not yet complete; most version-specific features are pre
                               Store 20(color) 46
               48:          10 Load 22(ucol)
                               Store 47(param) 48
-              49:           2 FunctionCall 14(foo(vf4[s1518];) 47(param)
+              49:           2 FunctionCall 14(foo(vf4[s1521];) 47(param)
                               Return
                               FunctionEnd
-14(foo(vf4[s1518];):           2 Function None 12
+14(foo(vf4[s1521];):           2 Function None 12
            13(p):     11(ptr) FunctionParameter
               15:             Label
               54:     24(ptr) AccessChain 53(dupUcol) 23

Test/baseResults/spv.textureBuffer.vert.out

+spv.textureBuffer.vert
+Warning, version 450 is not yet complete; most version-specific features are present, but some are missing.
+
+// Module Version 10000
+// Generated by (magic number): 80001
+// Id's are bound by 42
+
+                              Capability Shader
+                              Capability SampledBuffer
+               1:             ExtInstImport  "GLSL.std.450"
+                              MemoryModel Logical GLSL450
+                              EntryPoint Vertex 4  "main"
+                              Source GLSL 450
+                              Name 4  "main"
+                              Name 9  "tBuf"
+                              Name 13  "s"
+                              Name 23  "sBuf"
+                              Name 32  "utBuf"
+                              Name 38  "itBuf"
+                              Decorate 9(tBuf) DescriptorSet 0
+                              Decorate 13(s) DescriptorSet 0
+                              Decorate 23(sBuf) DescriptorSet 0
+                              Decorate 32(utBuf) DescriptorSet 0
+                              Decorate 38(itBuf) DescriptorSet 0
+               2:             TypeVoid
+               3:             TypeFunction 2
+               6:             TypeFloat 32
+               7:             TypeImage 6(float) Buffer sampled format:Unknown
+               8:             TypePointer UniformConstant 7
+         9(tBuf):      8(ptr) Variable UniformConstant
+              11:             TypeSampler
+              12:             TypePointer UniformConstant 11
+           13(s):     12(ptr) Variable UniformConstant
+              15:             TypeSampledImage 7
+              17:             TypeInt 32 1
+              18:     17(int) Constant 13
+              20:             TypeVector 6(float) 4
+              22:             TypePointer UniformConstant 15
+        23(sBuf):     22(ptr) Variable UniformConstant
+              29:             TypeInt 32 0
+              30:             TypeImage 29(int) Buffer sampled format:Unknown
+              31:             TypePointer UniformConstant 30
+       32(utBuf):     31(ptr) Variable UniformConstant
+              34:             TypeVector 29(int) 4
+              36:             TypeImage 17(int) Buffer sampled format:Unknown
+              37:             TypePointer UniformConstant 36
+       38(itBuf):     37(ptr) Variable UniformConstant
+              40:             TypeVector 17(int) 4
+         4(main):           2 Function None 3
+               5:             Label
+              10:           7 Load 9(tBuf)
+              14:          11 Load 13(s)
+              16:          15 SampledImage 10 14
+              19:           7 Image 16
+              21:   20(fvec4) ImageFetch 19 18
+              24:          15 Load 23(sBuf)
+              25:           7 Image 24
+              26:   20(fvec4) ImageFetch 25 18
+              27:           7 Load 9(tBuf)
+              28:   20(fvec4) ImageFetch 27 18
+              33:          30 Load 32(utBuf)
+              35:   34(ivec4) ImageFetch 33 18
+              39:          36 Load 38(itBuf)
+              41:   40(ivec4) ImageFetch 39 18
+                              Return
+                              FunctionEnd

Test/spv.textureBuffer.vert

+#version 450
+
+uniform textureBuffer tBuf;
+uniform sampler s;
+uniform samplerBuffer sBuf;
+
+uniform utextureBuffer utBuf;
+uniform itextureBuffer itBuf;
+
+void main()
+{
+    texelFetch(samplerBuffer(tBuf, s), 13);
+    texelFetch(sBuf, 13);
+    texelFetch(tBuf, 13);
+    texelFetch(utBuf, 13);
+    texelFetch(itBuf, 13);
+}

glslang/MachineIndependent/Initialize.cpp

@@ -3844,6 +3844,15 @@ void TBuiltIns::add2ndGenerationSamplingImaging(int version, EProfile profile, c
                             else {
                                 addSamplingFunctions(sampler, typeName, version, profile);
                                 addGatherFunctions(sampler, typeName, version, profile);
+                                if (spvVersion.vulkan > 0 && sampler.dim == EsdBuffer && sampler.isCombined()) {
+                                    // Vulkan wants a textureBuffer to allow texelFetch() --
+                                    // a sampled image with no sampler.
+                                    // So, add sampling functions for both the
+                                    // samplerBuffer and textureBuffer types.
+                                    sampler.setTexture(sampler.type, sampler.dim, sampler.arrayed, sampler.shadow,
+                                                       sampler.ms);
+                                    addSamplingFunctions(sampler, sampler.getString(), version, profile);
+                                }
                             }
                         }
                     }

gtests/Spv.FromFile.cpp

@@ -283,6 +283,7 @@ INSTANTIATE_TEST_CASE_P(
         "spv.test.vert",
         "spv.texture.frag",
         "spv.texture.vert",
+        "spv.textureBuffer.vert",
         "spv.image.frag",
         "spv.types.frag",
         "spv.uint.frag",