From 933d84217f76dc662ad49a6c6aa798db822e79dc Mon Sep 17 00:00:00 2001 From: Matt Birkholz Date: Mon, 11 Sep 2017 18:57:34 -0700 Subject: [PATCH] microcode/cmpauxmd/x86-64.m4: Wordsmith commentary. --- src/microcode/cmpauxmd/x86-64.m4 | 52 +++++++++++++++----------------- 1 file changed, 24 insertions(+), 28 deletions(-) diff --git a/src/microcode/cmpauxmd/x86-64.m4 b/src/microcode/cmpauxmd/x86-64.m4 index b7a19c93d..a03136cc4 100644 --- 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. ### 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. #### 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')', -- 2.25.1