fix lbArg_Ignore logic

Fixes #2698

src/llvm_abi.cpp

@@ -192,7 +192,7 @@ gb_internal void lb_add_function_type_attributes(LLVMValueRef fn, lbFunctionType
 	// } 
 	LLVMSetFunctionCallConv(fn, cc_kind);
 	if (calling_convention == ProcCC_Odin) {
-		unsigned context_index = offset+arg_count;
+		unsigned context_index = arg_index;
 		LLVMAddAttributeAtIndex(fn, context_index, noalias_attr);
 		LLVMAddAttributeAtIndex(fn, context_index, nonnull_attr);
 		LLVMAddAttributeAtIndex(fn, context_index, nocapture_attr);

src/llvm_backend_proc.cpp

@@ -578,7 +578,10 @@ gb_internal void lb_begin_procedure_body(lbProcedure *p) {
 				defer (param_index += 1);
 
 				if (arg_type->kind == lbArg_Ignore) {
-					continue;
+					// Even though it is an ignored argument, it might still be referenced in the
+					// body.
+					lbValue dummy = lb_add_local_generated(p, e->type, false).addr;
+					lb_add_entity(p->module, e, dummy);
 				} 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);
@@ -1051,6 +1054,7 @@ gb_internal lbValue lb_emit_call(lbProcedure *p, lbValue value, Array<lbValue> c
 			Type *original_type = e->type;
 			lbArgType *arg = &ft->args[param_index];
 			if (arg->kind == lbArg_Ignore) {
+				param_index += 1;
 				continue;
 			}