[mono][llvm] Run a few llvm passes on the emitted methods to reduce memory usage. (#97744)

Extracted from #97096.

Author: Johan Lorensson <lateralusx.github@gmail.com>

Author: vargaz

src/mono/mono/mini/mini-llvm.c

@@ -29,8 +29,12 @@
 #define __STDC_CONSTANT_MACROS
 #endif
 
+#include "llvm-c/Core.h"
 #include "llvm-c/BitWriter.h"
 #include "llvm-c/Analysis.h"
+#include "llvm-c/Transforms/InstCombine.h"
+#include "llvm-c/Transforms/Scalar.h"
+#include "llvm-c/Transforms/IPO.h"
 
 #include "mini-llvm-cpp.h"
 #include "llvm-jit.h"
@@ -138,6 +142,7 @@ typedef struct {
 	GHashTable *no_method_table_lmethods;
 	GHashTable *intrins_id_to_intrins;
 	GHashTable *intrins_id_to_type;
+	LLVMPassManagerRef func_pass_manager;
 } MonoLLVMModule;
 
 /*
@@ -13337,6 +13342,11 @@ emit_method_inner (EmitContext *ctx)
 #endif
 	} else {
 		//LLVMVerifyFunction (method, 0);
+		if (ctx->module->func_pass_manager) {
+			LLVMInitializeFunctionPassManager (ctx->module->func_pass_manager);
+			LLVMRunFunctionPassManager(ctx->module->func_pass_manager, ctx->lmethod);
+			LLVMFinalizeFunctionPassManager (ctx->module->func_pass_manager);
+		}
 		llvm_jit_finalize_method (ctx);
 	}
 
@@ -13856,13 +13866,22 @@ mono_llvm_create_aot_module (MonoAssembly *assembly, const char *global_prefix,
 		LLVMSetLinkage (module->sentinel_exception, LLVMExternalLinkage);
 		mono_llvm_set_is_constant (module->sentinel_exception);
 	}
+
+	module->func_pass_manager = LLVMCreateFunctionPassManagerForModule (module->lmodule);
+	if (module->func_pass_manager) {
+		LLVMAddCFGSimplificationPass (module->func_pass_manager);
+		LLVMAddInstructionCombiningPass (module->func_pass_manager);
+	}
 }
 
 void
 mono_llvm_free_aot_module (void)
 {
 	MonoLLVMModule *module = &aot_module;
 
+	if (module->func_pass_manager)
+		LLVMDisposePassManager (module->func_pass_manager);
+
 	if (module->lmodule)
 		LLVMDisposeModule (module->lmodule);