096e967aad
This reverts commit 6a3a742a6c.
The above commit has number of faults starting from the motivation down
to the actual implementation.
1. Faulty implementation.
The original code contained functions like:
NORETURN void nlr_jump(void *val) {
nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
nlr_buf_t *top = *top_ptr;
...
__asm volatile (
"mov %0, %%edx \n" // %edx points to nlr_buf
"mov 28(%%edx), %%esi \n" // load saved %esi
"mov 24(%%edx), %%edi \n" // load saved %edi
"mov 20(%%edx), %%ebx \n" // load saved %ebx
"mov 16(%%edx), %%esp \n" // load saved %esp
"mov 12(%%edx), %%ebp \n" // load saved %ebp
"mov 8(%%edx), %%eax \n" // load saved %eip
"mov %%eax, (%%esp) \n" // store saved %eip to stack
"xor %%eax, %%eax \n" // clear return register
"inc %%al \n" // increase to make 1, non-local return
"ret \n" // return
: // output operands
: "r"(top) // input operands
: // clobbered registers
);
}
Which clearly stated that C-level variable should be a parameter of the
assembly, whcih then moved it into correct register.
Whereas now it's:
NORETURN void nlr_jump_tail(nlr_buf_t *top) {
(void)top;
__asm volatile (
"mov 28(%edx), %esi \n" // load saved %esi
"mov 24(%edx), %edi \n" // load saved %edi
"mov 20(%edx), %ebx \n" // load saved %ebx
"mov 16(%edx), %esp \n" // load saved %esp
"mov 12(%edx), %ebp \n" // load saved %ebp
"mov 8(%edx), %eax \n" // load saved %eip
"mov %eax, (%esp) \n" // store saved %eip to stack
"xor %eax, %eax \n" // clear return register
"inc %al \n" // increase to make 1, non-local return
"ret \n" // return
);
for (;;); // needed to silence compiler warning
}
Which just tries to perform operations on a completely random register (edx
in this case). The outcome is the expected: saving the pure random luck of
the compiler putting the right value in the random register above, there's
a crash.
2. Non-critical assessment.
The original commit message says "There is a small overhead introduced
(typically 1 machine instruction)". That machine instruction is a call
if a compiler doesn't perform tail optimization (happens regularly), and
it's 1 instruction only with the broken code shown above, fixing it
requires adding more. With inefficiencies already presented in the NLR
code, the overhead becomes "considerable" (several times more than 1%),
not "small".
The commit message also says "This eliminates duplicated code.". An
obvious way to eliminate duplication would be to factor out common code
to macros, not introduce overhead and breakage like above.
3. Faulty motivation.
All this started with a report of warnings/errors happening for a niche
compiler. It could have been solved in one the direct ways: a) fixing it
just for affected compiler(s); b) rewriting it in proper assembly (like
it was before BTW); c) by not doing anything at all, MICROPY_NLR_SETJMP
exists exactly to address minor-impact cases like thar (where a) or b) are
not applicable). Instead, a backwards "solution" was put forward, leading
to all the issues above.
The best action thus appears to be revert and rework, not trying to work
around what went haywire in the first place.
145 lines
5.5 KiB
C
145 lines
5.5 KiB
C
/*
|
|
* This file is part of the MicroPython project, http://micropython.org/
|
|
*
|
|
* The MIT License (MIT)
|
|
*
|
|
* Copyright (c) 2013-2016 Damien P. George
|
|
*
|
|
* Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
* of this software and associated documentation files (the "Software"), to deal
|
|
* in the Software without restriction, including without limitation the rights
|
|
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
* copies of the Software, and to permit persons to whom the Software is
|
|
* furnished to do so, subject to the following conditions:
|
|
*
|
|
* The above copyright notice and this permission notice shall be included in
|
|
* all copies or substantial portions of the Software.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
|
* THE SOFTWARE.
|
|
*/
|
|
|
|
#include "py/mpstate.h"
|
|
|
|
#if (!defined(MICROPY_NLR_SETJMP) || !MICROPY_NLR_SETJMP) && (defined(__thumb2__) || defined(__thumb__) || defined(__arm__))
|
|
|
|
#undef nlr_push
|
|
|
|
// We only need the functions here if we are on arm/thumb, and we are not
|
|
// using setjmp/longjmp.
|
|
//
|
|
// For reference, arm/thumb callee save regs are:
|
|
// r4-r11, r13=sp
|
|
|
|
__attribute__((naked)) unsigned int nlr_push(nlr_buf_t *nlr) {
|
|
|
|
__asm volatile (
|
|
"str r4, [r0, #12] \n" // store r4 into nlr_buf
|
|
"str r5, [r0, #16] \n" // store r5 into nlr_buf
|
|
"str r6, [r0, #20] \n" // store r6 into nlr_buf
|
|
"str r7, [r0, #24] \n" // store r7 into nlr_buf
|
|
|
|
#if defined(__ARM_ARCH_6M__)
|
|
"mov r1, r8 \n"
|
|
"str r1, [r0, #28] \n" // store r8 into nlr_buf
|
|
"mov r1, r9 \n"
|
|
"str r1, [r0, #32] \n" // store r9 into nlr_buf
|
|
"mov r1, r10 \n"
|
|
"str r1, [r0, #36] \n" // store r10 into nlr_buf
|
|
"mov r1, r11 \n"
|
|
"str r1, [r0, #40] \n" // store r11 into nlr_buf
|
|
"mov r1, r13 \n"
|
|
"str r1, [r0, #44] \n" // store r13=sp into nlr_buf
|
|
"mov r1, lr \n"
|
|
"str r1, [r0, #8] \n" // store lr into nlr_buf
|
|
#else
|
|
"str r8, [r0, #28] \n" // store r8 into nlr_buf
|
|
"str r9, [r0, #32] \n" // store r9 into nlr_buf
|
|
"str r10, [r0, #36] \n" // store r10 into nlr_buf
|
|
"str r11, [r0, #40] \n" // store r11 into nlr_buf
|
|
"str r13, [r0, #44] \n" // store r13=sp into nlr_buf
|
|
"str lr, [r0, #8] \n" // store lr into nlr_buf
|
|
#endif
|
|
|
|
#if defined(__ARM_ARCH_6M__)
|
|
"ldr r1, nlr_push_tail_var \n"
|
|
"bx r1 \n" // do the rest in C
|
|
".align 2 \n"
|
|
"nlr_push_tail_var: .word nlr_push_tail \n"
|
|
#else
|
|
"b nlr_push_tail \n" // do the rest in C
|
|
#endif
|
|
);
|
|
|
|
return 0; // needed to silence compiler warning
|
|
}
|
|
|
|
__attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr) {
|
|
nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
|
|
nlr->prev = *top;
|
|
MP_NLR_SAVE_PYSTACK(nlr);
|
|
*top = nlr;
|
|
return 0; // normal return
|
|
}
|
|
|
|
void nlr_pop(void) {
|
|
nlr_buf_t **top = &MP_STATE_THREAD(nlr_top);
|
|
*top = (*top)->prev;
|
|
}
|
|
|
|
NORETURN __attribute__((naked)) void nlr_jump(void *val) {
|
|
nlr_buf_t **top_ptr = &MP_STATE_THREAD(nlr_top);
|
|
nlr_buf_t *top = *top_ptr;
|
|
if (top == NULL) {
|
|
nlr_jump_fail(val);
|
|
}
|
|
|
|
top->ret_val = val;
|
|
MP_NLR_RESTORE_PYSTACK(top);
|
|
*top_ptr = top->prev;
|
|
|
|
__asm volatile (
|
|
"mov r0, %0 \n" // r0 points to nlr_buf
|
|
"ldr r4, [r0, #12] \n" // load r4 from nlr_buf
|
|
"ldr r5, [r0, #16] \n" // load r5 from nlr_buf
|
|
"ldr r6, [r0, #20] \n" // load r6 from nlr_buf
|
|
"ldr r7, [r0, #24] \n" // load r7 from nlr_buf
|
|
|
|
#if defined(__ARM_ARCH_6M__)
|
|
"ldr r1, [r0, #28] \n" // load r8 from nlr_buf
|
|
"mov r8, r1 \n"
|
|
"ldr r1, [r0, #32] \n" // load r9 from nlr_buf
|
|
"mov r9, r1 \n"
|
|
"ldr r1, [r0, #36] \n" // load r10 from nlr_buf
|
|
"mov r10, r1 \n"
|
|
"ldr r1, [r0, #40] \n" // load r11 from nlr_buf
|
|
"mov r11, r1 \n"
|
|
"ldr r1, [r0, #44] \n" // load r13=sp from nlr_buf
|
|
"mov r13, r1 \n"
|
|
"ldr r1, [r0, #8] \n" // load lr from nlr_buf
|
|
"mov lr, r1 \n"
|
|
#else
|
|
"ldr r8, [r0, #28] \n" // load r8 from nlr_buf
|
|
"ldr r9, [r0, #32] \n" // load r9 from nlr_buf
|
|
"ldr r10, [r0, #36] \n" // load r10 from nlr_buf
|
|
"ldr r11, [r0, #40] \n" // load r11 from nlr_buf
|
|
"ldr r13, [r0, #44] \n" // load r13=sp from nlr_buf
|
|
"ldr lr, [r0, #8] \n" // load lr from nlr_buf
|
|
#endif
|
|
"movs r0, #1 \n" // return 1, non-local return
|
|
"bx lr \n" // return
|
|
: // output operands
|
|
: "r"(top) // input operands
|
|
: // clobbered registers
|
|
);
|
|
|
|
for (;;); // needed to silence compiler warning
|
|
}
|
|
|
|
#endif // (!defined(MICROPY_NLR_SETJMP) || !MICROPY_NLR_SETJMP) && (defined(__thumb2__) || defined(__thumb__) || defined(__arm__))
|