Use GLSLANG_ANGLE to strip features to what ANGLE requires

This change strips a few features similar to GLSLANG_WEB but doesn't
remove every detail like the latter.  It also hardcodes profile/version
to core/450.

In particular, TBuiltIns::initialize is specialized to remove most of
what is not supported or won't be supported by ANGLE.  The result of
this function is parsed with TParseContext::parseShaderStrings which is
a performance bottleneck.

This change shaves about 300KB off of ANGLE's binary size and reduces
the cost of SetupBuiltinSymbolTable to nearly a sixth.

Signed-off-by: Shahbaz Youssefi <[email protected]>

Author: ShabbyX

BUILD.gn

@@ -109,7 +109,6 @@ template("glslang_sources_common") {
       "SPIRV/SpvBuilder.cpp",
       "SPIRV/SpvBuilder.h",
       "SPIRV/SpvPostProcess.cpp",
-      "SPIRV/SpvTools.cpp",
       "SPIRV/SpvTools.h",
       "SPIRV/bitutils.h",
       "SPIRV/disassemble.cpp",
@@ -208,8 +207,12 @@ template("glslang_sources_common") {
 
     defines = []
     if (invoker.enable_opt) {
+      sources += [ "SPIRV/SpvTools.cpp" ]
       defines += [ "ENABLE_OPT=1" ]
     }
+    if (invoker.is_angle) {
+      defines += [ "GLSLANG_ANGLE" ]
+    }
 
     if (is_win) {
       sources += [ "glslang/OSDependent/Windows/ossource.cpp" ]
@@ -257,11 +260,13 @@ template("glslang_sources_common") {
 glslang_sources_common("glslang_lib_sources") {
   enable_opt = !glslang_angle
   enable_hlsl = !glslang_angle
+  is_angle = glslang_angle
 }
 
 glslang_sources_common("glslang_sources") {
   enable_opt = true
   enable_hlsl = true
+  is_angle = false
 }
 
 source_set("glslang_default_resource_limits_sources") {

SPIRV/GlslangToSpv.cpp

@@ -283,6 +283,8 @@ spv::SourceLanguage TranslateSourceLanguage(glslang::EShSource source, EProfile
 {
 #ifdef GLSLANG_WEB
     return spv::SourceLanguageESSL;
+#elif defined(GLSLANG_ANGLE)
+    return spv::SourceLanguageGLSL;
 #endif
 
     switch (source) {
@@ -8694,7 +8696,7 @@ void OutputSpvBin(const std::vector<unsigned int>& spirv, const char* baseName)
 // Write SPIR-V out to a text file with 32-bit hexadecimal words
 void OutputSpvHex(const std::vector<unsigned int>& spirv, const char* baseName, const char* varName)
 {
-#ifndef GLSLANG_WEB
+#if !defined(GLSLANG_WEB) && !defined(GLSLANG_ANGLE)
     std::ofstream out;
     out.open(baseName, std::ios::binary | std::ios::out);
     if (out.fail())