You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
330 lines
17 KiB
HTML
330 lines
17 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Frame Layout - GNU Compiler Collection (GCC) Internals</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="GNU Compiler Collection (GCC) Internals">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="Stack-and-Calling.html#Stack-and-Calling" title="Stack and Calling">
|
|
<link rel="next" href="Exception-Handling.html#Exception-Handling" title="Exception Handling">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
Copyright (C) 1988-2015 Free Software Foundation, Inc.
|
|
|
|
Permission is granted to copy, distribute and/or modify this document
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
|
any later version published by the Free Software Foundation; with the
|
|
Invariant Sections being ``Funding Free Software'', the Front-Cover
|
|
Texts being (a) (see below), and with the Back-Cover Texts being (b)
|
|
(see below). A copy of the license is included in the section entitled
|
|
``GNU Free Documentation License''.
|
|
|
|
(a) The FSF's Front-Cover Text is:
|
|
|
|
A GNU Manual
|
|
|
|
(b) The FSF's Back-Cover Text is:
|
|
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
|
software. Copies published by the Free Software Foundation raise
|
|
funds for GNU development.-->
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<style type="text/css"><!--
|
|
pre.display { font-family:inherit }
|
|
pre.format { font-family:inherit }
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
|
pre.smallexample { font-size:smaller }
|
|
pre.smalllisp { font-size:smaller }
|
|
span.sc { font-variant:small-caps }
|
|
span.roman { font-family:serif; font-weight:normal; }
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<a name="Frame-Layout"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="Exception-Handling.html#Exception-Handling">Exception Handling</a>,
|
|
Up: <a rel="up" accesskey="u" href="Stack-and-Calling.html#Stack-and-Calling">Stack and Calling</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h4 class="subsection">17.9.1 Basic Stack Layout</h4>
|
|
|
|
<p><a name="index-stack-frame-layout-4143"></a><a name="index-frame-layout-4144"></a>
|
|
<!-- prevent bad page break with this line -->
|
|
Here is the basic stack layout.
|
|
|
|
<div class="defun">
|
|
— Macro: <b>STACK_GROWS_DOWNWARD</b><var><a name="index-STACK_005fGROWS_005fDOWNWARD-4145"></a></var><br>
|
|
<blockquote><p>Define this macro if pushing a word onto the stack moves the stack
|
|
pointer to a smaller address.
|
|
|
|
<p>When we say, “define this macro if <small class="dots">...</small>”, it means that the
|
|
compiler checks this macro only with <code>#ifdef</code> so the precise
|
|
definition used does not matter.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>STACK_PUSH_CODE</b><var><a name="index-STACK_005fPUSH_005fCODE-4146"></a></var><br>
|
|
<blockquote><p>This macro defines the operation used when something is pushed
|
|
on the stack. In RTL, a push operation will be
|
|
<code>(set (mem (STACK_PUSH_CODE (reg sp))) ...)</code>
|
|
|
|
<p>The choices are <code>PRE_DEC</code>, <code>POST_DEC</code>, <code>PRE_INC</code>,
|
|
and <code>POST_INC</code>. Which of these is correct depends on
|
|
the stack direction and on whether the stack pointer points
|
|
to the last item on the stack or whether it points to the
|
|
space for the next item on the stack.
|
|
|
|
<p>The default is <code>PRE_DEC</code> when <code>STACK_GROWS_DOWNWARD</code> is
|
|
defined, which is almost always right, and <code>PRE_INC</code> otherwise,
|
|
which is often wrong.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>FRAME_GROWS_DOWNWARD</b><var><a name="index-FRAME_005fGROWS_005fDOWNWARD-4147"></a></var><br>
|
|
<blockquote><p>Define this macro to nonzero value if the addresses of local variable slots
|
|
are at negative offsets from the frame pointer.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>ARGS_GROW_DOWNWARD</b><var><a name="index-ARGS_005fGROW_005fDOWNWARD-4148"></a></var><br>
|
|
<blockquote><p>Define this macro if successive arguments to a function occupy decreasing
|
|
addresses on the stack.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>STARTING_FRAME_OFFSET</b><var><a name="index-STARTING_005fFRAME_005fOFFSET-4149"></a></var><br>
|
|
<blockquote><p>Offset from the frame pointer to the first local variable slot to be allocated.
|
|
|
|
<p>If <code>FRAME_GROWS_DOWNWARD</code>, find the next slot's offset by
|
|
subtracting the first slot's length from <code>STARTING_FRAME_OFFSET</code>.
|
|
Otherwise, it is found by adding the length of the first slot to the
|
|
value <code>STARTING_FRAME_OFFSET</code>.
|
|
<!-- i'm not sure if the above is still correct.. had to change it to get -->
|
|
<!-- rid of an overfull. -mew 2feb93 -->
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>STACK_ALIGNMENT_NEEDED</b><var><a name="index-STACK_005fALIGNMENT_005fNEEDED-4150"></a></var><br>
|
|
<blockquote><p>Define to zero to disable final alignment of the stack during reload.
|
|
The nonzero default for this macro is suitable for most ports.
|
|
|
|
<p>On ports where <code>STARTING_FRAME_OFFSET</code> is nonzero or where there
|
|
is a register save block following the local block that doesn't require
|
|
alignment to <code>STACK_BOUNDARY</code>, it may be beneficial to disable
|
|
stack alignment and do it in the backend.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>STACK_POINTER_OFFSET</b><var><a name="index-STACK_005fPOINTER_005fOFFSET-4151"></a></var><br>
|
|
<blockquote><p>Offset from the stack pointer register to the first location at which
|
|
outgoing arguments are placed. If not specified, the default value of
|
|
zero is used. This is the proper value for most machines.
|
|
|
|
<p>If <code>ARGS_GROW_DOWNWARD</code>, this is the offset to the location above
|
|
the first location at which outgoing arguments are placed.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>FIRST_PARM_OFFSET</b> (<var>fundecl</var>)<var><a name="index-FIRST_005fPARM_005fOFFSET-4152"></a></var><br>
|
|
<blockquote><p>Offset from the argument pointer register to the first argument's
|
|
address. On some machines it may depend on the data type of the
|
|
function.
|
|
|
|
<p>If <code>ARGS_GROW_DOWNWARD</code>, this is the offset to the location above
|
|
the first argument's address.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>STACK_DYNAMIC_OFFSET</b> (<var>fundecl</var>)<var><a name="index-STACK_005fDYNAMIC_005fOFFSET-4153"></a></var><br>
|
|
<blockquote><p>Offset from the stack pointer register to an item dynamically allocated
|
|
on the stack, e.g., by <code>alloca</code>.
|
|
|
|
<p>The default value for this macro is <code>STACK_POINTER_OFFSET</code> plus the
|
|
length of the outgoing arguments. The default is correct for most
|
|
machines. See <samp><span class="file">function.c</span></samp> for details.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>INITIAL_FRAME_ADDRESS_RTX</b><var><a name="index-INITIAL_005fFRAME_005fADDRESS_005fRTX-4154"></a></var><br>
|
|
<blockquote><p>A C expression whose value is RTL representing the address of the initial
|
|
stack frame. This address is passed to <code>RETURN_ADDR_RTX</code> and
|
|
<code>DYNAMIC_CHAIN_ADDRESS</code>. If you don't define this macro, a reasonable
|
|
default value will be used. Define this macro in order to make frame pointer
|
|
elimination work in the presence of <code>__builtin_frame_address (count)</code> and
|
|
<code>__builtin_return_address (count)</code> for <code>count</code> not equal to zero.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>DYNAMIC_CHAIN_ADDRESS</b> (<var>frameaddr</var>)<var><a name="index-DYNAMIC_005fCHAIN_005fADDRESS-4155"></a></var><br>
|
|
<blockquote><p>A C expression whose value is RTL representing the address in a stack
|
|
frame where the pointer to the caller's frame is stored. Assume that
|
|
<var>frameaddr</var> is an RTL expression for the address of the stack frame
|
|
itself.
|
|
|
|
<p>If you don't define this macro, the default is to return the value
|
|
of <var>frameaddr</var>—that is, the stack frame address is also the
|
|
address of the stack word that points to the previous frame.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>SETUP_FRAME_ADDRESSES</b><var><a name="index-SETUP_005fFRAME_005fADDRESSES-4156"></a></var><br>
|
|
<blockquote><p>If defined, a C expression that produces the machine-specific code to
|
|
setup the stack so that arbitrary frames can be accessed. For example,
|
|
on the SPARC, we must flush all of the register windows to the stack
|
|
before we can access arbitrary stack frames. You will seldom need to
|
|
define this macro.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Target Hook: rtx <b>TARGET_BUILTIN_SETJMP_FRAME_VALUE</b> (<var>void</var>)<var><a name="index-TARGET_005fBUILTIN_005fSETJMP_005fFRAME_005fVALUE-4157"></a></var><br>
|
|
<blockquote><p>This target hook should return an rtx that is used to store
|
|
the address of the current frame into the built in <code>setjmp</code> buffer.
|
|
The default value, <code>virtual_stack_vars_rtx</code>, is correct for most
|
|
machines. One reason you may need to define this target hook is if
|
|
<code>hard_frame_pointer_rtx</code> is the appropriate value on your machine.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>FRAME_ADDR_RTX</b> (<var>frameaddr</var>)<var><a name="index-FRAME_005fADDR_005fRTX-4158"></a></var><br>
|
|
<blockquote><p>A C expression whose value is RTL representing the value of the frame
|
|
address for the current frame. <var>frameaddr</var> is the frame pointer
|
|
of the current frame. This is used for __builtin_frame_address.
|
|
You need only define this macro if the frame address is not the same
|
|
as the frame pointer. Most machines do not need to define it.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>RETURN_ADDR_RTX</b> (<var>count, frameaddr</var>)<var><a name="index-RETURN_005fADDR_005fRTX-4159"></a></var><br>
|
|
<blockquote><p>A C expression whose value is RTL representing the value of the return
|
|
address for the frame <var>count</var> steps up from the current frame, after
|
|
the prologue. <var>frameaddr</var> is the frame pointer of the <var>count</var>
|
|
frame, or the frame pointer of the <var>count</var> − 1 frame if
|
|
<code>RETURN_ADDR_IN_PREVIOUS_FRAME</code> is nonzero.
|
|
|
|
<p>The value of the expression must always be the correct address when
|
|
<var>count</var> is zero, but may be <code>NULL_RTX</code> if there is no way to
|
|
determine the return address of other frames.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>RETURN_ADDR_IN_PREVIOUS_FRAME</b><var><a name="index-RETURN_005fADDR_005fIN_005fPREVIOUS_005fFRAME-4160"></a></var><br>
|
|
<blockquote><p>Define this macro to nonzero value if the return address of a particular
|
|
stack frame is accessed from the frame pointer of the previous stack
|
|
frame. The zero default for this macro is suitable for most ports.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>INCOMING_RETURN_ADDR_RTX</b><var><a name="index-INCOMING_005fRETURN_005fADDR_005fRTX-4161"></a></var><br>
|
|
<blockquote><p>A C expression whose value is RTL representing the location of the
|
|
incoming return address at the beginning of any function, before the
|
|
prologue. This RTL is either a <code>REG</code>, indicating that the return
|
|
value is saved in ‘<samp><span class="samp">REG</span></samp>’, or a <code>MEM</code> representing a location in
|
|
the stack.
|
|
|
|
<p>You only need to define this macro if you want to support call frame
|
|
debugging information like that provided by DWARF 2.
|
|
|
|
<p>If this RTL is a <code>REG</code>, you should also define
|
|
<code>DWARF_FRAME_RETURN_COLUMN</code> to <code>DWARF_FRAME_REGNUM (REGNO)</code>.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>DWARF_ALT_FRAME_RETURN_COLUMN</b><var><a name="index-DWARF_005fALT_005fFRAME_005fRETURN_005fCOLUMN-4162"></a></var><br>
|
|
<blockquote><p>A C expression whose value is an integer giving a DWARF 2 column
|
|
number that may be used as an alternative return column. The column
|
|
must not correspond to any gcc hard register (that is, it must not
|
|
be in the range of <code>DWARF_FRAME_REGNUM</code>).
|
|
|
|
<p>This macro can be useful if <code>DWARF_FRAME_RETURN_COLUMN</code> is set to a
|
|
general register, but an alternative column needs to be used for signal
|
|
frames. Some targets have also used different frame return columns
|
|
over time.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>DWARF_ZERO_REG</b><var><a name="index-DWARF_005fZERO_005fREG-4163"></a></var><br>
|
|
<blockquote><p>A C expression whose value is an integer giving a DWARF 2 register
|
|
number that is considered to always have the value zero. This should
|
|
only be defined if the target has an architected zero register, and
|
|
someone decided it was a good idea to use that register number to
|
|
terminate the stack backtrace. New ports should avoid this.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Target Hook: void <b>TARGET_DWARF_HANDLE_FRAME_UNSPEC</b> (<var>const char *label, rtx pattern, int index</var>)<var><a name="index-TARGET_005fDWARF_005fHANDLE_005fFRAME_005fUNSPEC-4164"></a></var><br>
|
|
<blockquote><p>This target hook allows the backend to emit frame-related insns that
|
|
contain UNSPECs or UNSPEC_VOLATILEs. The DWARF 2 call frame debugging
|
|
info engine will invoke it on insns of the form
|
|
<pre class="smallexample"> (set (reg) (unspec [...] UNSPEC_INDEX))
|
|
</pre>
|
|
<p>and
|
|
<pre class="smallexample"> (set (reg) (unspec_volatile [...] UNSPECV_INDEX)).
|
|
</pre>
|
|
<p>to let the backend emit the call frame instructions. <var>label</var> is
|
|
the CFI label attached to the insn, <var>pattern</var> is the pattern of
|
|
the insn and <var>index</var> is <code>UNSPEC_INDEX</code> or <code>UNSPECV_INDEX</code>.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>INCOMING_FRAME_SP_OFFSET</b><var><a name="index-INCOMING_005fFRAME_005fSP_005fOFFSET-4165"></a></var><br>
|
|
<blockquote><p>A C expression whose value is an integer giving the offset, in bytes,
|
|
from the value of the stack pointer register to the top of the stack
|
|
frame at the beginning of any function, before the prologue. The top of
|
|
the frame is defined to be the value of the stack pointer in the
|
|
previous frame, just before the call instruction.
|
|
|
|
<p>You only need to define this macro if you want to support call frame
|
|
debugging information like that provided by DWARF 2.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>ARG_POINTER_CFA_OFFSET</b> (<var>fundecl</var>)<var><a name="index-ARG_005fPOINTER_005fCFA_005fOFFSET-4166"></a></var><br>
|
|
<blockquote><p>A C expression whose value is an integer giving the offset, in bytes,
|
|
from the argument pointer to the canonical frame address (cfa). The
|
|
final value should coincide with that calculated by
|
|
<code>INCOMING_FRAME_SP_OFFSET</code>. Which is unfortunately not usable
|
|
during virtual register instantiation.
|
|
|
|
<p>The default value for this macro is
|
|
<code>FIRST_PARM_OFFSET (fundecl) + crtl->args.pretend_args_size</code>,
|
|
which is correct for most machines; in general, the arguments are found
|
|
immediately before the stack frame. Note that this is not the case on
|
|
some targets that save registers into the caller's frame, such as SPARC
|
|
and rs6000, and so such targets need to define this macro.
|
|
|
|
<p>You only need to define this macro if the default is incorrect, and you
|
|
want to support call frame debugging information like that provided by
|
|
DWARF 2.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>FRAME_POINTER_CFA_OFFSET</b> (<var>fundecl</var>)<var><a name="index-FRAME_005fPOINTER_005fCFA_005fOFFSET-4167"></a></var><br>
|
|
<blockquote><p>If defined, a C expression whose value is an integer giving the offset
|
|
in bytes from the frame pointer to the canonical frame address (cfa).
|
|
The final value should coincide with that calculated by
|
|
<code>INCOMING_FRAME_SP_OFFSET</code>.
|
|
|
|
<p>Normally the CFA is calculated as an offset from the argument pointer,
|
|
via <code>ARG_POINTER_CFA_OFFSET</code>, but if the argument pointer is
|
|
variable due to the ABI, this may not be possible. If this macro is
|
|
defined, it implies that the virtual register instantiation should be
|
|
based on the frame pointer instead of the argument pointer. Only one
|
|
of <code>FRAME_POINTER_CFA_OFFSET</code> and <code>ARG_POINTER_CFA_OFFSET</code>
|
|
should be defined.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>CFA_FRAME_BASE_OFFSET</b> (<var>fundecl</var>)<var><a name="index-CFA_005fFRAME_005fBASE_005fOFFSET-4168"></a></var><br>
|
|
<blockquote><p>If defined, a C expression whose value is an integer giving the offset
|
|
in bytes from the canonical frame address (cfa) to the frame base used
|
|
in DWARF 2 debug information. The default is zero. A different value
|
|
may reduce the size of debug information on some ports.
|
|
</p></blockquote></div>
|
|
|
|
</body></html>
|
|
|