Fix #2178: Allow specialization constants for texel offsets.

Test/baseResults/spv.specTexture.frag.out

+spv.specTexture.frag
+// Module Version 10000
+// Generated by (magic number): 80008
+// Id's are bound by 23
+
+                              Capability Shader
+               1:             ExtInstImport  "GLSL.std.450"
+                              MemoryModel Logical GLSL450
+                              EntryPoint Fragment 4  "main" 9
+                              ExecutionMode 4 OriginLowerLeft
+                              Source GLSL 450
+                              Name 4  "main"
+                              Name 9  "color_out"
+                              Name 13  "tex"
+                              Name 19  "offs"
+                              Decorate 9(color_out) Location 0
+                              Decorate 13(tex) DescriptorSet 0
+                              Decorate 13(tex) Binding 0
+                              Decorate 19(offs) SpecId 1
+               2:             TypeVoid
+               3:             TypeFunction 2
+               6:             TypeFloat 32
+               7:             TypeVector 6(float) 4
+               8:             TypePointer Output 7(fvec4)
+    9(color_out):      8(ptr) Variable Output
+              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:    6(float) Constant 0
+              17:   15(fvec2) ConstantComposite 16 16
+              18:             TypeInt 32 1
+        19(offs):     18(int) SpecConstant 0
+              20:             TypeVector 18(int) 2
+              21:   20(ivec2) SpecConstantComposite 19(offs) 19(offs)
+         4(main):           2 Function None 3
+               5:             Label
+              14:          11 Load 13(tex)
+              22:    7(fvec4) ImageSampleExplicitLod 14 17 Lod ConstOffset 16 21
+                              Store 9(color_out) 22
+                              Return
+                              FunctionEnd

Test/spv.specTexture.frag

+#version 450
+
+layout(constant_id = 1) const int offs = 0;
+layout(binding = 0) uniform sampler2D tex;
+layout(location = 0) out vec4 color_out;
+
+void main(void)
+{
+  color_out = textureLodOffset(tex, vec2(0.0, 0.0), 0.0, ivec2(offs, offs));
+}
\ No newline at end of file

glslang/MachineIndependent/ParseHelper.cpp

@@ -2013,18 +2013,20 @@ void TParseContext::builtInOpCheck(const TSourceLoc& loc, const TFunction& fnCan
         if (arg > 0) {
 
 #ifndef GLSLANG_WEB
-            bool f16ShadowCompare = (*argp)[1]->getAsTyped()->getBasicType() == EbtFloat16 && arg0->getType().getSampler().shadow;
+            bool f16ShadowCompare = (*argp)[1]->getAsTyped()->getBasicType() == EbtFloat16 &&
+                                    arg0->getType().getSampler().shadow;
             if (f16ShadowCompare)
                 ++arg;
 #endif
-            if (! (*argp)[arg]->getAsConstantUnion())
+            if (! (*argp)[arg]->getAsTyped()->getQualifier().isConstant())
                 error(loc, "argument must be compile-time constant", "texel offset", "");
-            else {
+            else if ((*argp)[arg]->getAsConstantUnion()) {
                 const TType& type = (*argp)[arg]->getAsTyped()->getType();
                 for (int c = 0; c < type.getVectorSize(); ++c) {
                     int offset = (*argp)[arg]->getAsConstantUnion()->getConstArray()[c].getIConst();
                     if (offset > resources.maxProgramTexelOffset || offset < resources.minProgramTexelOffset)
-                        error(loc, "value is out of range:", "texel offset", "[gl_MinProgramTexelOffset, gl_MaxProgramTexelOffset]");
+                        error(loc, "value is out of range:", "texel offset",
+                              "[gl_MinProgramTexelOffset, gl_MaxProgramTexelOffset]");
                 }
             }
         }

gtests/Spv.FromFile.cpp

@@ -598,6 +598,7 @@ INSTANTIATE_TEST_CASE_P(
         "spv.glFragColor.frag",
         "spv.rankShift.comp",
         "spv.specConst.vert",
+        "spv.specTexture.frag",
         "spv.OVR_multiview.vert",
         "spv.xfbOffsetOnBlockMembersAssignment.vert",
         "spv.xfbOffsetOnStructMembersAssignment.vert",