add optimization transforms

compiler.c

@@ -5,6 +5,10 @@
 #include <llvm-c/Core.h>
 #include <llvm-c/Analysis.h>
 #include <llvm-c/BitWriter.h>
+#include <llvm-c/Transforms/PassManagerBuilder.h>
+#include <llvm-c/Transforms/InstCombine.h>
+#include <llvm-c/Transforms/Scalar.h>
+#include <llvm-c/Transforms/Utils.h>
 
 #include "y.tab.h"
 #include "ast.h"
@@ -643,9 +647,24 @@ int main(int argc, char *argv[])
     LLVMVerifyModule(module, LLVMAbortProcessAction, &error);
     LLVMDisposeMessage(error);
 
+    LLVMPassManagerRef passManager = LLVMCreatePassManager();
+    LLVMAddInstructionCombiningPass(passManager);
+    LLVMAddCFGSimplificationPass(passManager);
+    LLVMAddReassociatePass(passManager);
+    LLVMAddPromoteMemoryToRegisterPass(passManager);
+
+    LLVMPassManagerBuilderRef passManagerBuilder = LLVMPassManagerBuilderCreate();
+    LLVMPassManagerBuilderSetOptLevel(passManagerBuilder, 3);
+    LLVMPassManagerBuilderPopulateModulePassManager(passManagerBuilder, passManager);
+
+    LLVMRunPassManager(passManager, module);
+
     if (LLVMWriteBitcodeToFile(module, "test.bc") != 0) {
         fprintf(stderr, "error writing bitcode to file\n");
     }
 
+    LLVMPassManagerBuilderDispose(passManagerBuilder);
+    LLVMDisposePassManager(passManager);
+    LLVMDisposeModule(module);
     return 0;
 }