From fa1ea21f75601a93827d143bb9074b1f7474a953 Mon Sep 17 00:00:00 2001 From: Damien George Date: Tue, 15 Aug 2023 14:34:25 +1000 Subject: [PATCH] esp32/gccollect: Make level arg volatile to force recursive function. Otherwise the compiler may inline the gc_collect_inner() function and/or remove the recursion, which is necessary to spill all the windowed registers to the C stack. Signed-off-by: Damien George --- ports/esp32/gccollect.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-) diff --git a/ports/esp32/gccollect.c b/ports/esp32/gccollect.c index e16e8028ad..4b6dd8ab61 100644 --- a/ports/esp32/gccollect.c +++ b/ports/esp32/gccollect.c @@ -39,30 +39,25 @@ #include "xtensa/hal.h" -static void gc_collect_inner(int level) { +// The level argument must be volatile to force the compiler to emit code that +// will call this function recursively, to nest the C stack. +static void gc_collect_inner(volatile unsigned int level) { if (level < XCHAL_NUM_AREGS / 8) { + // Go deeper on the stack to spill more registers from the register window. gc_collect_inner(level + 1); - if (level != 0) { - return; - } - } - - if (level == XCHAL_NUM_AREGS / 8) { - // get the sp + } else { + // Deep enough so that all registers are on the C stack, now trace the stack. volatile uint32_t sp = (uint32_t)esp_cpu_get_sp(); gc_collect_root((void **)sp, ((mp_uint_t)MP_STATE_THREAD(stack_top) - sp) / sizeof(uint32_t)); - return; } - - // trace root pointers from any threads - #if MICROPY_PY_THREAD - mp_thread_gc_others(); - #endif } void gc_collect(void) { gc_collect_start(); gc_collect_inner(0); + #if MICROPY_PY_THREAD + mp_thread_gc_others(); + #endif gc_collect_end(); }