microcode/cmpauxmd/x86-64.m4: Wordsmith commentary.

diff --git a/src/microcode/cmpauxmd/x86-64.m4 b/src/microcode/cmpauxmd/x86-64.m4
index b7a19c93dd6d51ba7f109e3f363c0b18873cb806..a03136cc4a7aeffc89051257410d292b9f26fa4f 100644 (file)
--- a/src/microcode/cmpauxmd/x86-64.m4
+++ b/src/microcode/cmpauxmd/x86-64.m4
@@ -37,56 +37,55 @@
 ###
 ###    1) All registers and stack locations hold a C long object.
 ###
-###    2) The C compiler divides registers into three groups:
+###    2) The AMD64 Unix ABI divides registers into three groups:
+###
 ###    - Linkage registers, used for procedure calls and global
 ###    references.  On AMD64 Unix ABI: %rbp, %rsp.
-###    - super temporaries, not preserved accross procedure calls and
+###
+###    - super temporaries, not preserved across procedure calls and
 ###    always usable. On AMD64 Unix ABI: everything but what is
 ###    listed below.
+###
 ###    - preserved registers saved by the callee if they are written.
 ###    On AMD64 Unix ABI: %rbp, %rbx, %r12-%r15, MXCSR, x87 control
 ###    word.
 ###
-###    3) Arguments, if passed on a stack, are popped by the caller
-###    or by the procedure return instruction (as on the VAX).  Thus
-###    most "leaf" procedures need not worry about them.  On x86-64,
-###    arguments beyond the sixth are passed on the stack; the first
-###    through sixth are passed in %rdi, %rsi, %rdx, %rcx, %r8, or
-###    %r9.  (Non-integer arguments are passed in other ways.)
+###    3) Arguments beyond the sixth are passed on the stack; the
+###    first through sixth are passed in %rdi, %rsi, %rdx, %rcx, %r8,
+###    or %r9.  (Non-integer arguments are passed in other ways.)
 ###
-###    4) There is a hardware or software maintained stack for
-###    control.  The procedure calling sequence may leave return
-###    addresses in registers, but they must be saved somewhere for
-###    nested calls and recursive procedures.  On x86-64: saved on
-###    the stack by the CALL instruction.
+###    4) The C function calling sequence saves a return address on
+###    the stack using the CALL instruction.
 ###
-###    5) C procedures return long values in a super temporary
-###    register.  Two word structures are returned in super temporary
-###    registers as well in the AMD64 Unix ABI: %rax and %rdi.
+###    5) One and two word structures are returned in %rax and %rdi.
 ###
-###    6) Floating point registers are not preserved by this
-###    interface.  The interface is only called from the Scheme
-###    interpreter, which does not use floating point data.  Thus
-###    although the calling convention would require us to preserve
-###    them, they contain garbage.
+###    6) Floating point arguments are passed in the floating point
+###    registers.  The ABI requires callees to preserve these UNLESS
+###    it is known that no caller could be using them, which is the
+###    case here.  The only C functions calling compiled Scheme are
+###    in the interpreter which does not do floating point.
 ###
 ### Compiled Scheme code uses the following register convention:
+###
 ###    - %rsp contains the Scheme stack pointer, not the C stack
 ###    pointer.
+###
 ###    - %rsi contains a pointer to the Scheme interpreter's "register"
 ###    block.  This block contains the compiler's copy of MemTop,
 ###    the interpreter's registers (val, env, exp, etc.),
 ###    temporary locations for compiled code, and the addresses
 ###    of various hooks defined in this file.
+###
 ###    - %rdi contains the Scheme free pointer.
+###
 ###    - %rbp contains the Scheme datum mask.
 ###    The dynamic link (when needed) is in Registers[REGBLOCK_COMPILER_TEMP]
 ###    Values are returned in Registers[REGBLOCK_VAL]
 ###    [TRC 20091025: Later, we ought to use machine registers for
 ###    these.]
 ###
-###    All other registers are available to the compiler.  A
-###    caller-saves convention is used, so the registers need not be
+###    All other registers are available to the compiler.  A caller-
+###    saves convention is used, so the registers need not be
 ###    preserved by subprocedures.
 \f
 ### The following m4 macros can be defined to change how this file is
@@ -104,16 +103,14 @@
 ### SUPPRESS_LEADING_UNDERSCORE
 ###    If defined, external symbol names are generated as written;
 ###    otherwise, they have an underscore prepended to them.
-### WCC386
-###    Should be defined when using Watcom assembler.
+###
 ### WCC386R
 ###    Should be defined when using Watcom assembler and generating
 ###    code to use the Watcom register-based argument conventions.
+###
 ### TYPE_CODE_LENGTH
 ###    Normally defined to be 6.  Don't change this unless you know
 ###    what you're doing.
-### VALGRIND_MODE
-###    If defined, modify code to make it work with valgrind.
 \f
 ####   Utility macros and definitions
 
@@ -122,7 +119,6 @@ ifdef(`WIN32',
       `define(IF_WIN32,`')')
 
 IF_WIN32(`define(DASM,1)')
-ifdef(`WCC386R',`define(WCC386,1)')
 
 ifdef(`DASM',
       `define(IFDASM,`$1')',