gcc源代码分析，expand_call()函数和printf("Hello, world!\n");的关系

expand_call()函数在expr.c文件中。

下面是expand_call()函数的主要调试结果，记录之。

主要是加入了debug_tree()函数和debug_rtx()函数。

debug_tree()函数加入到了expand_expr()函数的开始。

debug_rtx()函数加入到了gen_rtx()函数的结束处。

emit_call_1()函数是何时调用的也能看出。emit_call_insn()是何时调用的也能看出。

主要的调试目的是expand_call()函数是如何生成rtx的？

既是如何一步步调用，在哪里调用gen_rtx()函数的？

当然只是针对hello.c文件中的：

printf("Hello, world!\n");

这一函数调用来分析的。

call_expr

expand_call
expand_expr code = 71
 <nop_expr 830d8
    type <pointer_type 9017c
        type <integer_type 90130 char readonly permanent QI
            size <integer_cst 81638 literal permanent 1
            align 8 size_unit 8 sep_unit 8 symtab 0
            sep <integer_cst 81608 literal permanent -128 precision 8 min <integer_cst 81608 -128>
            max <integer_cst 81620 literal permanent 127
            pointer_to_this <pointer_type 9017c>
        permanent unsigned SI
        size <integer_cst 8154c literal permanent 4
        align 32 size_unit 8 sep_unit 32 symtab 0
        chain <function_type 902c0>
    literal
    arg 0 <nop_expr 830c0
        type <pointer_type 87a44 type <integer_type 815bc char>
            permanent unsigned SI size <integer_cst 8154c 4>
            align 32 size_unit 8 sep_unit 32 symtab 0
            chain <array_type 87a90>
        literal
        arg 0 <addr_expr 830a8 type <pointer_type 93f58>
            literal
            arg 0 <string_cst 83014 type <array_type 93ef4>
                static literal "Hello, world!
"
expand_expr code = 71
 <nop_expr 830c0
    type <pointer_type 87a44
        type <integer_type 815bc char permanent QI
            size <integer_cst 81638 literal permanent 1
            align 8 size_unit 8 sep_unit 8 symtab 0
            sep <integer_cst 81608 literal permanent -128 precision 8 min <integer_cst 81608 -128>
            max <integer_cst 81620 literal permanent 127
            pointer_to_this <pointer_type 87a44> chain <integer_type 816a8 long int>
        permanent unsigned SI
        size <integer_cst 8154c literal permanent 4
        align 32 size_unit 8 sep_unit 32 symtab 0
        chain <array_type 87a90>
    literal
    arg 0 <addr_expr 830a8
        type <pointer_type 93f58 type <array_type 93ef4>
            unsigned SI size <integer_cst 8154c 4>
            align 32 size_unit 8 sep_unit 32 symtab 0
        literal
        arg 0 <string_cst 83014 type <array_type 93ef4>
            static literal "Hello, world!
"
expand_expr code = 74
 <addr_expr 830a8
    type <pointer_type 93f58
        type <array_type 93ef4 type <integer_type 815bc char>
            BLK
            size <integer_cst 93f40 literal 15
            align 8 size_unit 8 sep_unit 8 symtab 0
            sep <integer_cst 81638 literal permanent 1 domain <integer_type 93ea8>
            pointer_to_this <pointer_type 93f58> chain <pointer_type 93f58>
        unsigned SI
        size <integer_cst 8154c literal permanent 4
        align 32 size_unit 8 sep_unit 32 symtab 0
    literal
    arg 0 <string_cst 83014 type <array_type 93ef4>
        static literal "Hello, world!
"
expand_expr code = 26
 <string_cst 83014
    type <array_type 93ef4
        type <integer_type 815bc char permanent QI
            size <integer_cst 81638 literal permanent 1
            align 8 size_unit 8 sep_unit 8 symtab 0
            sep <integer_cst 81608 literal permanent -128 precision 8 min <integer_cst 81608 -128>
            max <integer_cst 81620 literal permanent 127
            pointer_to_this <pointer_type 87a44> chain <integer_type 816a8 long int>
        BLK
        size <integer_cst 93f40 literal 15
        align 8 size_unit 8 sep_unit 8 symtab 0 sep <integer_cst 81638 1>
        domain <integer_type 93ea8 SI
            size <integer_cst 8154c literal permanent 4
            align 32 size_unit 8 sep_unit 32 symtab 0
            sep <integer_cst 83048 literal 0 precision 32 min <integer_cst 83048 0>
            max <integer_cst 83078 literal 14
        pointer_to_this <pointer_type 93f58> chain <pointer_type 93f58>
    static literal "Hello, world!
"
output_constant_def

(symbol_ref:SI ("*LC0"))

(mem:BLK (symbol_ref:SI ("*LC0")))
this this
addr_expr
force_operand 27
end addr_expr

(pre_dec:SI (reg:SI 7))

(mem:SI (pre_dec:SI (reg:SI 7)))

(set (mem:SI (pre_dec:SI (reg:SI 7)))
   (symbol_ref:SI ("*LC0")))

(insn_list 6 (nil))

(insn_list 2 (insn_list 6 (nil)))

(sequence[ ] )

(reg:SI 0)

(const_int 4)
emit_call_1 funexp symbol_ref

(mem:QI (symbol_ref/v:SI ("printf")))

(call (mem:QI (symbol_ref/v:SI ("printf")))
   (const_int 4))

(set (reg:SI 0)
   (call (mem:QI (symbol_ref/v:SI ("printf")))
       (const_int 4)))
emit_call_insn
end expand_call
c_expand_return