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py/parse: Work around xtensa esp-2020r3 compiler bug.

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This commit works around a bug in xtensa-esp32-elf-gcc version esp-2020r3.

The bug is in generation of loop constructs.  The below code is generated
by the xtensa-esp32 compiler.  The first extract is the buggy machine code
and the second extract is the corrected machine code.  The test
`basics/logic_constfolding.py` fails with the first code and succeeds with
the second.

Disassembly of section .text.push_result_rule:

00000000 <push_result_rule>:
  ...
  d6:   209770       or      a9, a7, a7
  d9:   178976       loop    a9, f4 <push_result_rule+0xf4>
                     d9: R_XTENSA_SLOT0_OP   .text.push_result_rule+0xf4
  dc:   030190       rsr.lend        a9
  df:   130090       wsr.lbeg        a9
  e2:   a8c992       addi    a9, a9, -88
  e5:   06d992       addmi   a9, a9, 0x600
  e8:   130190       wsr.lend        a9
  eb:   002000       isync
  ee:   030290       rsr.lcount      a9
  f1:   01c992       addi    a9, a9, 1
  f4:   1494e7       bne     a4, a14, 10c <push_result_rule+0x10c>
                     f4: R_XTENSA_SLOT0_OP   .text.push_result_rule+0x10c

Disassembly of section .text.push_result_rule:

00000000 <push_result_rule>:
  ...
  d6:   209770       or      a9, a7, a7
  d9:   178976       loop    a9, f4 <push_result_rule+0xf4>
                     d9: R_XTENSA_SLOT0_OP   .text.push_result_rule+0xf4
  dc:   030190       rsr.lend        a9
  df:   130090       wsr.lbeg        a9
  e2:   000091       l32r    a9, fffc00e4 <push_result_rule+0xfffc00e4>
                     e2: R_XTENSA_SLOT0_OP   .literal.push_result_rule+0x18
  e5:   0020f0       nop
  e8:   130190       wsr.lend        a9
  eb:   002000       isync
  ee:   030290       rsr.lcount      a9
  f1:   01c992       addi    a9, a9, 1
  f4:   1494e7       bne     a4, a14, 10c <push_result_rule+0x10c>
                     f4: R_XTENSA_SLOT0_OP   .text.push_result_rule+0x10c

Work done in collaboration with @jimmo.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George
2022-06-09 12:36:45 +10:00
parent 3452ee58d3
commit f63b4f85aa
2 changed files with 12 additions and 0 deletions
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5
py/parse.c
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@@ -639,6 +639,11 @@ STATIC MP_DEFINE_CONST_MAP(mp_constants_map, mp_constants_table);
STATIC void push_result_rule(parser_t *parser, size_t src_line, uint8_t rule_id, size_t num_args);
#if MICROPY_COMP_CONST_FOLDING
#if MICROPY_COMP_CONST_FOLDING_COMPILER_WORKAROUND
// Some versions of the xtensa-esp32-elf-gcc compiler generate wrong code if this
// function is static, so provide a hook for them to work around this problem.
MP_NOINLINE
#endif
STATIC bool fold_logical_constants(parser_t *parser, uint8_t rule_id, size_t *num_args) {
if (rule_id == RULE_or_test
|| rule_id == RULE_and_test) {