X-Git-Url: http://git.hcoop.net/bpt/guile.git/blobdiff_plain/26b9f9090073c896762af3125af54958e153f8f2..89b235afd34482f2e7d2af553f43d0744895ee83:/libguile/frames.h?ds=sidebyside diff --git a/libguile/frames.h b/libguile/frames.h index 33432eb48..bd85b7e89 100644 --- a/libguile/frames.h +++ b/libguile/frames.h @@ -1,4 +1,4 @@ -/* Copyright (C) 2001, 2009, 2010 Free Software Foundation, Inc. +/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. * * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License @@ -23,90 +23,146 @@ #include "programs.h" -/* - * VM frames - */ +/* Stack frames + ------------ -/* - * It's a little confusing, but there are two representations of frames in this - * file: frame pointers and Scheme objects wrapping those frame pointers. The - * former uses the SCM_FRAME_... macro prefix, the latter SCM_VM_FRAME_.. - * prefix. - * - * The confusing thing is that only Scheme frame objects have functions that use - * them, and they use the scm_frame_.. prefix. Hysterical raisins. - */ + It's a little confusing, but there are two representations of frames + in this file: frame pointers, and Scheme objects wrapping those frame + pointers. The former uses the SCM_FRAME macro prefix, the latter + SCM_VM_FRAME prefix. + + The confusing thing is that only Scheme frame objects have functions + that use them, and they use the lower-case scm_frame prefix. -/* VM Frame Layout - --------------- + Stack frame layout + ------------------ + + /------------------\ + | Local N-1 | <- sp | ... | - | Intermed. val. 0 | <- fp + nargs + nlocs - +------------------+ - | Local variable 1 | - | Local variable 0 | <- fp + nargs - | Argument 1 | - | Argument 0 | <- fp = SCM_FRAME_STACK_ADDRESS (fp) - | Program | <- fp - 1 + | Local 1 | + | Local 0 | <- fp = SCM_FRAME_LOCALS_ADDRESS (fp) +==================+ - | Return address | <- SCM_FRAME_UPPER_ADDRESS (fp) - | MV return address| - | Dynamic link | <- fp - 4 = SCM_FRAME_DATA_ADDRESS (fp) = SCM_FRAME_LOWER_ADDRESS (fp) + | Return address | + | Dynamic link | <- fp - 2 = SCM_FRAME_LOWER_ADDRESS (fp) +==================+ - | | - - As can be inferred from this drawing, it is assumed that - `sizeof (SCM *) == sizeof (SCM)', since pointers (the `link' parts) are - assumed to be as long as SCM objects. */ - -#define SCM_FRAME_DATA_ADDRESS(fp) (fp - 4) -#define SCM_FRAME_STACK_ADDRESS(fp) (fp) -#define SCM_FRAME_UPPER_ADDRESS(fp) (fp - 2) -#define SCM_FRAME_LOWER_ADDRESS(fp) (fp - 4) - -#define SCM_FRAME_BYTE_CAST(x) ((scm_t_uint8 *) SCM_UNPACK (x)) -#define SCM_FRAME_STACK_CAST(x) ((SCM *) SCM_UNPACK (x)) - -#define SCM_FRAME_RETURN_ADDRESS(fp) \ - (SCM_FRAME_BYTE_CAST (SCM_FRAME_DATA_ADDRESS (fp)[2])) -#define SCM_FRAME_SET_RETURN_ADDRESS(fp, ra) \ - ((SCM_FRAME_DATA_ADDRESS (fp)[2])) = (SCM)(ra); -#define SCM_FRAME_MV_RETURN_ADDRESS(fp) \ - (SCM_FRAME_BYTE_CAST (SCM_FRAME_DATA_ADDRESS (fp)[1])) -#define SCM_FRAME_SET_MV_RETURN_ADDRESS(fp, mvra) \ - ((SCM_FRAME_DATA_ADDRESS (fp)[1])) = (SCM)(mvra); -#define SCM_FRAME_DYNAMIC_LINK(fp) \ - (SCM_FRAME_STACK_CAST (SCM_FRAME_DATA_ADDRESS (fp)[0])) -#define SCM_FRAME_SET_DYNAMIC_LINK(fp, dl) \ - ((SCM_FRAME_DATA_ADDRESS (fp)[0])) = (SCM)(dl); -#define SCM_FRAME_VARIABLE(fp,i) SCM_FRAME_STACK_ADDRESS (fp)[i] -#define SCM_FRAME_PROGRAM(fp) SCM_FRAME_STACK_ADDRESS (fp)[-1] + | | <- fp - 3 = SCM_FRAME_PREVIOUS_SP (fp) + + The calling convention is that a caller prepares a stack frame + consisting of the saved FP and the return address, followed by the + procedure and then the arguments to the call, in order. Thus in the + beginning of a call, the procedure being called is in slot 0, the + first argument is in slot 1, and the SP points to the last argument. + The number of arguments, including the procedure, is thus SP - FP + + 1. + + After ensuring that the correct number of arguments have been passed, + a function will set the stack pointer to point to the last local + slot. This lets a function allocate the temporary space that it + needs once in the beginning of the call, instead of pushing and + popping the stack pointer during the call's extent. + + When a program returns, it returns its values in the slots starting + from local 1, as if the values were arguments to a tail call. We + start from 1 instead of 0 for the convenience of the "values" builtin + function, which can just leave its arguments in place. + + The callee resets the stack pointer to point to the last value. In + this way the caller knows how many values there are: it's the number + of words between the stack pointer and the slot at which the caller + placed the procedure. + + After checking that the number of values returned is appropriate, the + caller shuffles the values around (if needed), and resets the stack + pointer back to its original value from before the call. */ + + + + +/* This structure maps to the contents of a VM stack frame. It can + alias a frame directly. */ +struct scm_vm_frame +{ + SCM *dynamic_link; + scm_t_uint32 *return_address; + SCM locals[1]; /* Variable-length */ +}; + +#define SCM_FRAME_LOWER_ADDRESS(fp) (((SCM *) (fp)) - 2) +#define SCM_FRAME_STRUCT(fp) \ + ((struct scm_vm_frame *) SCM_FRAME_LOWER_ADDRESS (fp)) +#define SCM_FRAME_LOCALS_ADDRESS(fp) (SCM_FRAME_STRUCT (fp)->locals) + +#define SCM_FRAME_PREVIOUS_SP(fp) (((SCM *) (fp)) - 3) + +#define SCM_FRAME_RETURN_ADDRESS(fp) \ + (SCM_FRAME_STRUCT (fp)->return_address) +#define SCM_FRAME_SET_RETURN_ADDRESS(fp, ra) \ + SCM_FRAME_STRUCT (fp)->return_address = (ra) +#define SCM_FRAME_DYNAMIC_LINK(fp) \ + (SCM_FRAME_STRUCT (fp)->dynamic_link) +#define SCM_FRAME_SET_DYNAMIC_LINK(fp, dl) \ + SCM_FRAME_DYNAMIC_LINK (fp) = (dl) +#define SCM_FRAME_LOCAL(fp,i) \ + (SCM_FRAME_STRUCT (fp)->locals[i]) + +#define SCM_FRAME_NUM_LOCALS(fp, sp) \ + ((sp) + 1 - &SCM_FRAME_LOCAL (fp, 0)) + +/* Currently (November 2013) we keep the procedure and arguments in + their slots for the duration of the procedure call, regardless of + whether the values are live or not. This allows for backtraces that + show the closure and arguments. We may allow the compiler to relax + this restriction in the future, if the user so desires. This would + conserve stack space and make GC more precise. We would need better + debugging information to do that, however. + + Even now there is an exception to the rule that slot 0 holds the + procedure, which is in the case of tail calls. The compiler will + emit code that shuffles the new procedure and arguments into position + before performing the tail call, so there is a window in which + SCM_FRAME_PROGRAM does not correspond to the program being executed. + + The moral of the story is to use the IP in a frame to determine what + procedure is being called. It is only appropriate to use + SCM_FRAME_PROGRAM in the prologue of a procedure call, when you know + it must be there. */ + +#define SCM_FRAME_PROGRAM(fp) (SCM_FRAME_LOCAL (fp, 0)) /* * Heap frames */ +#ifdef BUILDING_LIBGUILE + struct scm_frame { SCM stack_holder; - SCM *fp; - SCM *sp; - scm_t_uint8 *ip; - scm_t_ptrdiff offset; + scm_t_ptrdiff fp_offset; + scm_t_ptrdiff sp_offset; + scm_t_uint32 *ip; }; -#define SCM_VM_FRAME_P(x) (SCM_NIMP (x) && SCM_TYP7 (x) == scm_tc7_frame) +#define SCM_VM_FRAME_P(x) (SCM_HAS_TYP7 (x, scm_tc7_frame)) #define SCM_VM_FRAME_DATA(x) ((struct scm_frame*)SCM_CELL_WORD_1 (x)) #define SCM_VM_FRAME_STACK_HOLDER(f) SCM_VM_FRAME_DATA(f)->stack_holder -#define SCM_VM_FRAME_FP(f) SCM_VM_FRAME_DATA(f)->fp -#define SCM_VM_FRAME_SP(f) SCM_VM_FRAME_DATA(f)->sp +#define SCM_VM_FRAME_FP(f) (SCM_VM_FRAME_DATA(f)->fp_offset + scm_i_frame_stack_base(f)) +#define SCM_VM_FRAME_SP(f) (SCM_VM_FRAME_DATA(f)->sp_offset + scm_i_frame_stack_base(f)) #define SCM_VM_FRAME_IP(f) SCM_VM_FRAME_DATA(f)->ip -#define SCM_VM_FRAME_OFFSET(f) SCM_VM_FRAME_DATA(f)->offset +#define SCM_VM_FRAME_OFFSET(f) scm_i_frame_offset (f) #define SCM_VALIDATE_VM_FRAME(p,x) SCM_MAKE_VALIDATE (p, x, VM_FRAME_P) -SCM_API SCM scm_c_make_frame (SCM stack_holder, SCM *fp, SCM *sp, - scm_t_uint8 *ip, scm_t_ptrdiff offset); +SCM_INTERNAL SCM* scm_i_frame_stack_base (SCM frame); +SCM_INTERNAL scm_t_ptrdiff scm_i_frame_offset (SCM frame); + +SCM_INTERNAL SCM scm_c_make_frame (SCM stack_holder, scm_t_ptrdiff fp_offset, + scm_t_ptrdiff sp_offset, scm_t_uint32 *ip); + +#endif + SCM_API SCM scm_frame_p (SCM obj); SCM_API SCM scm_frame_procedure (SCM frame); SCM_API SCM scm_frame_arguments (SCM frame); @@ -114,9 +170,10 @@ SCM_API SCM scm_frame_source (SCM frame); SCM_API SCM scm_frame_num_locals (SCM frame); SCM_API SCM scm_frame_local_ref (SCM frame, SCM index); SCM_API SCM scm_frame_local_set_x (SCM frame, SCM index, SCM val); +SCM_API SCM scm_frame_address (SCM frame); +SCM_API SCM scm_frame_stack_pointer (SCM frame); SCM_API SCM scm_frame_instruction_pointer (SCM frame); SCM_API SCM scm_frame_return_address (SCM frame); -SCM_API SCM scm_frame_mv_return_address (SCM frame); SCM_API SCM scm_frame_dynamic_link (SCM frame); SCM_API SCM scm_frame_previous (SCM frame);