[PATCH] x86: make code generated for EXPR_INVOKEVIRTUAL shorter

[Tomek Grabiec]

We do not have to load object reference from stack with this instruction:

mov 0(%esp), %reg

Before we select the code for EXPR_INVOKEVIRTUAL code for call arguments
is selected so we know what register was allocated to the argument
representing object reference before it was pushed.

Signed-off-by: Tomek Grabiec <tgrab...@gmail.com>
---
 arch/x86/insn-selector_32.brg |   32 +++++++++++++++++++++++++++-----
 1 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/arch/x86/insn-selector_32.brg b/arch/x86/insn-selector_32.brg
index ffd31c5..7c380d9 100644
--- a/arch/x86/insn-selector_32.brg
+++ b/arch/x86/insn-selector_32.brg
@@ -84,6 +84,20 @@ static void method_args_cleanup(struct basic_block *bb, 
struct tree_node *tree,
        select_insn(bb, tree, imm_reg_insn(INSN_ADD_IMM_REG, args_size, 
stack_ptr));
 }
 
+/*
+ * Returns the right-most expression in argument list. It's the first
+ * argument passed to method.
+ */
+static struct expression *get_first_arg(struct tree_node *args)
+{
+       while (expr_type(to_expr(args)) == EXPR_ARGS_LIST)
+             args = to_expr(args)->args_right;
+
+       assert(expr_type(to_expr(args)) == EXPR_ARG);
+
+       return to_expr(to_expr(args)->arg_expression);
+}
+
 struct _MBState;
 
 static void __binop_reg_local(struct _MBState *, struct basic_block *, struct 
tree_node *, enum insn_type, struct var_info *, long);
@@ -612,11 +626,11 @@ reg:      EXPR_INVOKE(arg) 1
 reg:   EXPR_INVOKEVIRTUAL(arg) 1
 {
        struct var_info *eax, *edx = NULL;
+       struct expression *objectref_expr;
        struct var_info *call_target;
        struct compilation_unit *cu;
        unsigned long method_offset;
        struct vm_method *method;
-       struct var_info *stack_ptr;
        unsigned long args_count;
        struct expression *expr;
 
@@ -634,11 +648,15 @@ reg:      EXPR_INVOKEVIRTUAL(arg) 1
                state->reg2 = get_var(s->b_parent);
        }
 
-       call_target = get_var(s->b_parent);
-       stack_ptr = get_fixed_var(s->b_parent, REG_ESP);
-
        /* object reference */
-       select_insn(s, tree, membase_reg_insn(INSN_MOV_MEMBASE_REG, stack_ptr, 
0, call_target));
+       objectref_expr = get_first_arg(expr->args_list);
+
+       if (expr_type(objectref_expr) == EXPR_VALUE) {
+               call_target = get_var(s->b_parent);
+               select_insn(s, tree, imm_reg_insn(INSN_MOV_IMM_REG, 
objectref_expr->value, call_target));
+       } else {
+               call_target = state->left->reg1;
+       }
 
        /* object class */
        select_insn(s, tree, membase_reg_insn(INSN_MOV_MEMBASE_REG, 
call_target, offsetof(struct vm_object, class), call_target));
@@ -1047,6 +1065,7 @@ reg:      EXPR_CONVERSION(reg)
 
 arg:   EXPR_NO_ARGS
 {
+       state->reg1 = NULL;
 }
 
 arg:   EXPR_ARG(EXPR_VALUE)
@@ -1080,10 +1099,13 @@ arg:    EXPR_ARG(reg)
 
        src = state->left->reg1;
        select_insn(s, tree, reg_insn(INSN_PUSH_REG, src));
+
+       state->reg1 = src;
 }
 
 arg:   EXPR_ARGS_LIST(arg, arg)
 {
+       state->reg1 = state->right->reg1;
 }
 
 reg:   EXPR_EXCEPTION_REF
-- 
1.6.0.6


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