diff --git a/glslang/MachineIndependent/Initialize.cpp b/glslang/MachineIndependent/Initialize.cpp
index 2fcc32be..35b1c745 100644
--- a/glslang/MachineIndependent/Initialize.cpp
+++ b/glslang/MachineIndependent/Initialize.cpp
@@ -3838,12 +3838,13 @@ void TBuiltIns::initialize(int version, EProfile profile, const SpvVersion& spvV
     }
 
     // GL_AMD_gcn_shader
-    if (profile != EEsProfile && version >= 450) {
+    if (profile != EEsProfile && version >= 440) {
         commonBuiltins.append(
             "float cubeFaceIndexAMD(vec3);"
             "vec2  cubeFaceCoordAMD(vec3);"
             "uint64_t timeAMD();"
 
+            "in int gl_SIMDGroupSizeAMD;"
             "\n");
     }
 
@@ -7752,14 +7753,6 @@ void TBuiltIns::initialize(const TBuiltInResource &resources, int version, EProf
         s.append(builtInConstant);
     }
 
-#ifdef AMD_EXTENSIONS
-    // GL_AMD_gcn_shader
-    if (profile != EEsProfile && version >= 450) {
-        snprintf(builtInConstant, maxSize, "const int gl_SIMDGroupSizeAMD = 64;");
-        s.append(builtInConstant);
-    }
-#endif
-
 #ifdef NV_EXTENSIONS
     // SPV_NV_mesh_shader
     if ((profile != EEsProfile && version >= 450) || (profile == EEsProfile && version >= 320)) {
@@ -7911,6 +7904,7 @@ void TBuiltIns::identifyBuiltIns(int version, EProfile profile, const SpvVersion
             }
         }
 
+
 #ifdef AMD_EXTENSIONS
         if (profile != EEsProfile) {
             symbolTable.setFunctionExtensions("minInvocationsAMD",                1, &E_GL_AMD_shader_ballot);
@@ -7945,6 +7939,9 @@ void TBuiltIns::identifyBuiltIns(int version, EProfile profile, const SpvVersion
         }
 
         if (profile != EEsProfile) {
+            symbolTable.setVariableExtensions("gl_SIMDGroupSizeAMD", 1, &E_GL_AMD_gcn_shader);
+            SpecialQualifier("gl_SIMDGroupSizeAMD", EvqVaryingIn, EbvSubGroupSize, symbolTable);
+
             symbolTable.setFunctionExtensions("cubeFaceIndexAMD", 1, &E_GL_AMD_gcn_shader);
             symbolTable.setFunctionExtensions("cubeFaceCoordAMD", 1, &E_GL_AMD_gcn_shader);
             symbolTable.setFunctionExtensions("timeAMD",          1, &E_GL_AMD_gcn_shader);