The CGEN support code in opcodes accesses instruction contents using a
couple of functions defined in cgen-opc.c: cgen_get_insn_value and
cgen_put_insn_value. These functions use the "instruction endianness"
in the CPU description to order the read/written bytes.
The process of writing an instruction to the object file is:
a) cgen_put_insn_value ;; Writes out the opcodes.
b) ARCH_cgen_insert_operand
insert_normal
insert_1
cgen_put_insn_value ;; Writes out the bytes of the
;; operand.
Likewise, the process of reading an instruction from the object file
is:
a) cgen_get_insn_value ;; Reads the opcodes.
b) ARCH_cgen_extract_operand
extract_normal
extract_1
cgen_get_insn_value ;; Reads in the bytes of the
;; operand.
As can be seen above, cgen_{get,put}_insn_value are used to both
process the instruction opcodes (the constant fields conforming the
base instruction) and also the values of the instruction operands,
such as immediates.
This is problematic for architectures in which the endianness of
instructions is different to the endianness of data. An example is
BPF, where instructions are always encoded big-endian but the data may
be either big or little.
This patch changes the cgen_{get,put}_insn_value functions in order to
get an extra argument with the endianness to use, and adapts the
existin callers to these functions in order to provide cd->endian or
cd->insn_endian, whatever appropriate. Callers like extract_1 and
insert_1 pass cd->endian (since they are reading/writing operand
values) while callers reading/writing the base instruction pass
cd->insn_endian instead.
A few little adjustments have been needed in some existing CGEN based
ports:
* The BPF assembler uses cgen_put_insn_value. It has been adapted to
pass the new endian argument.
* The mep port has code in mep.opc that uses cgen_{get,put}_insn_value.
It has been adapted to pass the new endianargument. Ditto for a
call in the assembler.
Tested with --enable-targets=all.
Regested in all supported targets.
No regressions.
include/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* opcode/cgen.h: Get an `endian' argument in both
cgen_get_insn_value and cgen_put_insn_value.
opcodes/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* cgen-opc.c (cgen_get_insn_value): Get an `endian' argument.
(cgen_put_insn_value): Likewise.
(cgen_lookup_insn): Pass endianness to cgen_{get,put}_insn_value.
* cgen-dis.in (print_insn): Likewise.
* cgen-ibld.in (insert_1): Likewise.
(insert_1): Likewise.
(insert_insn_normal): Likewise.
(extract_1): Likewise.
* bpf-dis.c: Regenerate.
* bpf-ibld.c: Likewise.
* bpf-ibld.c: Likewise.
* cgen-dis.in: Likewise.
* cgen-ibld.in: Likewise.
* cgen-opc.c: Likewise.
* epiphany-dis.c: Likewise.
* epiphany-ibld.c: Likewise.
* fr30-dis.c: Likewise.
* fr30-ibld.c: Likewise.
* frv-dis.c: Likewise.
* frv-ibld.c: Likewise.
* ip2k-dis.c: Likewise.
* ip2k-ibld.c: Likewise.
* iq2000-dis.c: Likewise.
* iq2000-ibld.c: Likewise.
* lm32-dis.c: Likewise.
* lm32-ibld.c: Likewise.
* m32c-dis.c: Likewise.
* m32c-ibld.c: Likewise.
* m32r-dis.c: Likewise.
* m32r-ibld.c: Likewise.
* mep-dis.c: Likewise.
* mep-ibld.c: Likewise.
* mt-dis.c: Likewise.
* mt-ibld.c: Likewise.
* or1k-dis.c: Likewise.
* or1k-ibld.c: Likewise.
* xc16x-dis.c: Likewise.
* xc16x-ibld.c: Likewise.
* xstormy16-dis.c: Likewise.
* xstormy16-ibld.c: Likewise.
gas/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* cgen.c (gas_cgen_finish_insn): Pass the endianness to
cgen_put_insn_value.
(gas_cgen_md_apply_fix): Likewise.
(gas_cgen_md_apply_fix): Likewise.
* config/tc-bpf.c (md_apply_fix): Pass data endianness to
cgen_put_insn_value.
* config/tc-mep.c (mep_check_ivc2_scheduling): Pass endianness to
cgen_put_insn_value.
cpu/ChangeLog:
2020-06-02 Jose E. Marchesi <jose.marchesi@oracle.com>
* mep.opc (print_slot_insn): Pass the insn endianness to
cgen_get_insn_value.
The calculation of the shift amount, used to insert fields into the
instruction buffer, is not correct when the following conditions are all
true:
- CGEN_INT_INSN_P is defined, and true.
- CGEN_INSN_LSB0_P is true
- Total instruction length is greater than the length of a single
instruction word (the instruction is made of multiple words)
- The word offset is non-zero (the field is outside the first word)
When the above conditions are all true, the calculated shift fails to
take account of the total instruction length.
After this commit the calculation of the shift amount is split into two
parts, first we calculate the shift required to get to BIT0 of the word
in which the field lives, then we calculate the shift required to place
the field within the instruction word.
The change in this commit only effects the CGEN_INT_INSN_P defined true
case, but changes the code for both CGEN_INSN_LSB0_P true, and false.
In the case of CGEN_INSN_LSB0_P being false, the code used to say:
shift = total_length - (word_offset + start + length);
Now it says:
shift_to_word = total_length - (word_offset + word_length);
shift_within_word = word_length - start - length;
shift = shift_to_word + shift_within_word;
From which we can see that in all cases the computed shift value should
be unchanged.
In the case of CGEN_INSN_LSB0_P being true, the code used to say:
shift = (word_offset + start + 1) - length;
Now it says:
shift_to_word = total_length - (word_offset + word_length);
shift_within_word = start + 1 - length;
shift = shift_to_word + shift_within_word;
In the case where 'total_length == word_length' AND 'word_offset ==
0' (which indicates an instruction of a single word), we see that the
computed shift value will be unchanged. However, when the total_length
and word_length are different, and the word_offset is non-zero then the
computed shift value will be different (and correct).
opcodes/ChangeLog:
* cgen-ibld.in (insert_normal): Rework calculation of shift.
* epiphany-ibld.c: Regenerate.
* fr30-ibld.c: Regenerate.
* frv-ibld.c: Regenerate.
* ip2k-ibld.c: Regenerate.
* iq2000-ibld.c: Regenerate.
* lm32-ibld.c: Regenerate.
* m32c-ibld.c: Regenerate.
* m32r-ibld.c: Regenerate.
* mep-ibld.c: Regenerate.
* mt-ibld.c: Regenerate.
* or1k-ibld.c: Regenerate.
* xc16x-ibld.c: Regenerate.
* xstormy16-ibld.c: Regenerate.
Jose E. Marchesi
Alan Modra
Andrew Burgess
H.J. Lu
Doug Evans
Nick Clifton