Improve debug information for direct procedure parmaters

src/llvm_backend_debug.cpp

@@ -966,7 +966,7 @@ void lb_add_debug_local_variable(lbProcedure *p, LLVMValueRef ptr, Type *type, T
 }
 
 
-void lb_add_debug_param_variable(lbProcedure *p, LLVMValueRef ptr, Type *type, Token const &token, unsigned arg_number) {
+void lb_add_debug_param_variable(lbProcedure *p, LLVMValueRef ptr, Type *type, Token const &token, unsigned arg_number, lbBlock *block) {
 	if (p->debug_info == nullptr) {
 		return;
 	}
@@ -1020,7 +1020,6 @@ void lb_add_debug_param_variable(lbProcedure *p, LLVMValueRef ptr, Type *type, T
 	);
 
 	LLVMValueRef storage = ptr;
-	LLVMBasicBlockRef block = p->decl_block->block;
 	LLVMMetadataRef llvm_debug_loc = lb_debug_location_from_token_pos(p, token.pos);
 	LLVMMetadataRef llvm_expr = LLVMDIBuilderCreateExpression(m->debug_builder, nullptr, 0);
 	lb_set_llvm_metadata(m, ptr, llvm_expr);
@@ -1028,7 +1027,7 @@ void lb_add_debug_param_variable(lbProcedure *p, LLVMValueRef ptr, Type *type, T
 	// NOTE(bill, 2022-02-01): For parameter values, you must insert them at the end of the decl block
 	// The reason is that if the parameter is at index 0 and a pointer, there is not such things as an
 	// instruction "before" it.
-	LLVMDIBuilderInsertDbgValueAtEnd(m->debug_builder, storage, var_info, llvm_expr, llvm_debug_loc, block);
+	LLVMDIBuilderInsertDbgValueAtEnd(m->debug_builder, storage, var_info, llvm_expr, llvm_debug_loc, block->block);
 }
 
 

src/llvm_backend_proc.cpp

@@ -480,9 +480,8 @@ void lb_begin_procedure_body(lbProcedure *p) {
 				} else if (arg_type->kind == lbArg_Direct) {
 					if (e->token.string.len != 0 && !is_blank_ident(e->token.string)) {
 						LLVMTypeRef param_type = lb_type(p->module, e->type);
-						LLVMValueRef value = LLVMGetParam(p->value, param_offset+param_index);
-
-						value = OdinLLVMBuildTransmute(p, value, param_type);
+						LLVMValueRef original_value = LLVMGetParam(p->value, param_offset+param_index);
+						LLVMValueRef value = OdinLLVMBuildTransmute(p, original_value, param_type);
 
 						lbValue param = {};
 						param.value = value;
@@ -491,8 +490,16 @@ void lb_begin_procedure_body(lbProcedure *p) {
 						lbValue ptr = lb_address_from_load_or_generate_local(p, param);
 						GB_ASSERT(LLVMIsAAllocaInst(ptr.value));
 						lb_add_entity(p->module, e, ptr);
-						// lb_add_debug_param_variable(p, ptr.value, e->type, e->token, param_index+1);
-						lb_add_debug_param_variable(p, value, e->type, e->token, param_index+1);
+
+						lbBlock *block = p->decl_block;
+						if (original_value != value) {
+							block = p->curr_block;
+						}
+						LLVMValueRef debug_storage_value = value;
+						if (original_value != value && LLVMIsALoadInst(value)) {
+							debug_storage_value = ptr.value;
+						}
+						lb_add_debug_param_variable(p, debug_storage_value, e->type, e->token, param_index+1, block);
 					}
 				} else if (arg_type->kind == lbArg_Indirect) {
 					if (e->token.string.len != 0 && !is_blank_ident(e->token.string)) {
@@ -500,7 +507,7 @@ void lb_begin_procedure_body(lbProcedure *p) {
 						ptr.value = LLVMGetParam(p->value, param_offset+param_index);
 						ptr.type = alloc_type_pointer(e->type);
 						lb_add_entity(p->module, e, ptr);
-						lb_add_debug_param_variable(p, ptr.value, e->type, e->token, param_index+1);
+						lb_add_debug_param_variable(p, ptr.value, e->type, e->token, param_index+1, p->decl_block);
 					}
 				}
 			}