[spirv] Legalization: use CCP and enable on HS/DS/GS (#948)

external/SPIRV-Tools

@@ -1 +1 @@
-Subproject commit c9a881ecc6f304b586bf13f54a7cff7119b04070
+Subproject commit 4ba9dcc8a05bb0266e46135c6a48311dbc62524e

tools/clang/lib/SPIRV/SPIRVEmitter.cpp

@@ -233,6 +233,7 @@ bool spirvToolsLegalize(std::vector<uint32_t> *module, std::string *messages) {
   optimizer.RegisterPass(spvtools::CreateScalarReplacementPass());
   optimizer.RegisterPass(spvtools::CreateLocalMultiStoreElimPass());
   optimizer.RegisterPass(spvtools::CreateInsertExtractElimPass());
+  optimizer.RegisterPass(spvtools::CreateCCPPass());
   optimizer.RegisterPass(spvtools::CreateDeadBranchElimPass());
   optimizer.RegisterPass(spvtools::CreateCFGCleanupPass());
   optimizer.RegisterPass(spvtools::CreateAggressiveDCEPass());