bpf: gas: consolidate handling of immediate overflows
This commit changes the BPF GAS port in order to handle immediate
overflows the same way than the clang BPF assembler:
- For an immediate field of N bits, any written number (positive or
negative) whose two's complement encoding fit in N its is accepted.
This means that -2 is the same than 0xffffffe. It is up to the
instructions to decide how to interpret the encoded value.
- Immediate fields in jump instructions are no longer relaxed.
Relaxing to jump instructions with wider range is only performed
when expressions are involved.
- The manual is updated to document this, and testsuite adapted
accordingly.
Tested in x86_64-linux-gnu host, bpf-unknown-none target.
gas/ChangeLog:
2023-08-17 Jose E. Marchesi <jose.marchesi@oracle.com>
* config/tc-bpf.c (check_immediate_overflow): New function.
(encode_insn): Use check_immediate_overflow.
(md_assemble): Do not relax instructions with
constant disp16 fields.
* doc/c-bpf.texi (BPF Instructions): Add note about how numerical
literal values are interpreted for instruction immediate operands.
* testsuite/gas/bpf/disp16-overflow.s: Adapt accordingly.
* testsuite/gas/bpf/jump-relax-jump.s: Likewise.
* testsuite/gas/bpf/jump-relax-jump.d: Likewise.
* testsuite/gas/bpf/jump-relax-jump-be.d: Likewise.
* testsuite/gas/bpf/jump-relax-ja.s: Likewise.
* testsuite/gas/bpf/jump-relax-ja.d: Likewise.
* testsuite/gas/bpf/jump-relax-ja-be.d: Likewise.
* testsuite/gas/bpf/disp16-overflow-relax.l: Likewise.
* testsuite/gas/bpf/imm32-overflow.s: Likewise.
* testsuite/gas/bpf/disp32-overflow.s: Likewise.
* testsuite/gas/bpf/disp16-overflow.l: Likewise.
* testsuite/gas/bpf/disp32-overflow.l: Likewise.
* testsuite/gas/bpf/imm32-overflow.l: Likewise.
* testsuite/gas/bpf/offset16-overflow.l: Likewise.
20 files changed
