jit: better module stripping (#2743)

gen/dynamiccompile.cpp

@@ -169,6 +169,22 @@ void iterateFuncInstructions(llvm::Function &func, F &&handler) {
   }     // for (auto &&bb : fun)
 }
 
+template<typename I>
+void stripDeclarations(llvm::iterator_range<I> range) {
+  for (auto it = range.begin(); it != range.end();) {
+    auto elem = &(*it);
+    ++it;
+    if (elem->isDeclaration() && elem->use_empty()) {
+      elem->eraseFromParent();
+    }
+  }
+}
+
+void stripModule(llvm::Module &module) {
+  stripDeclarations(module.functions());
+  stripDeclarations(module.globals());
+}
+
 void fixRtModule(llvm::Module &newModule,
                  const decltype(IRState::dynamicCompiledFunctions) &funcs) {
   std::unordered_map<std::string, std::string> thunkVar2func;
@@ -224,6 +240,8 @@ void fixRtModule(llvm::Module &newModule,
       }
     }
   }
+
+  stripModule(newModule);
 }
 
 void removeFunctionsTargets(IRState *irs, llvm::Module &module) {

tests/dynamiccompile/jit_module_stripping.d

@@ -1,6 +1,7 @@
 
 // RUN: %ldc -enable-dynamic-compile -run %s
 
+import std.stdio;
 import std.array;
 import std.string;
 import ldc.attributes;
@@ -8,6 +9,7 @@ import ldc.dynamic_compile;
 
 __gshared int value = 32;
 
+
 @dynamicCompile int foo()
 {
   return 42;
@@ -27,6 +29,11 @@ void fun(int function())
   fun(&foo);
 }
 
+@dynamicCompile int bzz()
+{
+  return value;
+}
+
 class Foo()
 {
   @dynamicCompile int foo()
@@ -35,6 +42,27 @@ class Foo()
   }
 }
 
+struct UnusedStruct1
+{
+  int i;
+  int j;
+};
+
+struct UnusedStruct2
+{
+  UnusedStruct1 f;
+  int k;
+}
+
+void unusedfunc1(UnusedStruct2)
+{
+}
+
+void unusedfunc2(int function())
+{
+}
+
+__gshared int unusedvalue = 32;
 
 void main(string[] args)
 {
@@ -44,10 +72,20 @@ void main(string[] args)
   {
     if (DumpStage.OriginalModule == stage)
     {
+      write(str);
       dump.put(str);
     }
   };
+  writeln("===========================================");
   compileDynamicCode(settings);
+  writeln("===========================================");
 
   assert(0 == count(dump.data, "thunk"));
+  assert(0 == count(dump.data, "unusedvalue"));
+  assert(0 == count(dump.data, "unusedfunc1"));
+  assert(0 == count(dump.data, "unusedfunc2"));
+
+  // TODO: these symbols is pulled by llvm.ldc.typeinfo
+  //assert(0 == count(dump.data, "UnusedStruct1"));
+  //assert(0 == count(dump.data, "UnusedStruct2"));
 }