From afba3e054041bbad961fad61df7c4797ab35d9e3 Mon Sep 17 00:00:00 2001 From: Damien George Date: Wed, 31 Jul 2024 12:33:33 +1000 Subject: [PATCH] py/emitnative: Fix case of clobbered REG_TEMP0 when loading const obj. The `emit_load_reg_with_object()` helper function will clobber `REG_TEMP0`. This is currently OK on architectures where `REG_RET` and `REG_TEMP0` are the same (all architectures except RV32), because all callers of `emit_load_reg_with_object()` use either `REG_RET` or `REG_TEMP0` as the destination register. But on RV32 these registers are different and so when `REG_RET` is the destination, `REG_TEMP0` is clobbered, leading to incorrectly generated machine code. This commit fixes the issue simply by using `REG_TEMP0` as the destination register for all uses of `emit_load_reg_with_object()`, and adds a comment to make sure the caller of this function is careful. Signed-off-by: Damien George --- py/emitnative.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/py/emitnative.c b/py/emitnative.c index 88ebf0bfcf3de..66c345b233d76 100644 --- a/py/emitnative.c +++ b/py/emitnative.c @@ -357,6 +357,7 @@ static void emit_native_mov_reg_qstr(emit_t *emit, int arg_reg, qstr qst) { #endif } +// This function may clobber REG_TEMP0 (and `reg_dest` can be REG_TEMP0). static void emit_native_mov_reg_qstr_obj(emit_t *emit, int reg_dest, qstr qst) { #if MICROPY_PERSISTENT_CODE_SAVE emit_load_reg_with_object(emit, reg_dest, MP_OBJ_NEW_QSTR(qst)); @@ -1117,6 +1118,7 @@ static exc_stack_entry_t *emit_native_pop_exc_stack(emit_t *emit) { return e; } +// This function will clobber REG_TEMP0 (and `reg` can be REG_TEMP0). static void emit_load_reg_with_object(emit_t *emit, int reg, mp_obj_t obj) { emit->scope->scope_flags |= MP_SCOPE_FLAG_HASCONSTS; size_t table_off = mp_emit_common_use_const_obj(emit->emit_common, obj); @@ -1391,9 +1393,9 @@ static void emit_native_load_const_str(emit_t *emit, qstr qst) { static void emit_native_load_const_obj(emit_t *emit, mp_obj_t obj) { emit_native_pre(emit); - need_reg_single(emit, REG_RET, 0); - emit_load_reg_with_object(emit, REG_RET, obj); - emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET); + need_reg_single(emit, REG_TEMP0, 0); + emit_load_reg_with_object(emit, REG_TEMP0, obj); + emit_post_push_reg(emit, VTYPE_PYOBJ, REG_TEMP0); } static void emit_native_load_null(emit_t *emit) { pFad - Phonifier reborn

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