This code was trying to save temporary argument registers in interrupt
handler functions that contain calls. With the exception that all FP
registers are saved including the normally callee saved registers.
If all of the callees use an FP ABI and the interrupt handler doesn't
touch the normally callee saved FP registers, we don't need to save
them.
It doesn't appear that we need to special case functions with calls. The
normal callee saved register handling will already check each of the calls
and consider a register clobbered if the call doesn't explicitly say it is preserved.
All of the test changes are from the removal of the FP callee saved
registers. There are tests for interrupt handlers with F and D extension
that use ilp32 or lp64 ABIs that are not affected by this change. They
still save the FP callee saved registers as they should.
gcc appears to have a bug where the D extension being enabled with the
ilp32f or lp64f ABI does not save the FP callee saved regs. The callee
would only save/restore the lower 32 bits and clobber the upper bits.
LLVM saves the FP callee saved regs in this case and there is an
unchanged test for it.
The unnecessary save/restore was raised in this thread
https://discourse.llvm.org/t/has-bugs-when-optimizing-save-restore-csrs-by-changing-csr-xlen-f32-interrupt/78200/1
This commit includes the necessary changes to clang and LLVM to support
codegen of `RVE` and the `ilp32e`/`lp64e` ABIs.
The differences between `RVE` and `RVI` are:
* `RVE` reduces the integer register count to 16(x0-x16).
* The ABI should be `ilp32e` for 32 bits and `lp64e` for 64 bits.
`RVE` can be combined with all current standard extensions.
The central changes in ilp32e/lp64e ABI, compared to ilp32/lp64 are:
* Only 6 integer argument registers (rather than 8).
* Only 2 callee-saved registers (rather than 12).
* A Stack Alignment of 32bits (rather than 128bits).
* ilp32e isn't compatible with D ISA extension.
If `ilp32e` or `lp64` is used with an ISA that has any of the registers
x16-x31 and f0-f31, then these registers are considered temporaries.
To be compatible with the implementation of ilp32e in GCC, we don't use
aligned registers to pass variadic arguments and set stack alignment\
to 4-bytes for types with length of 2*XLEN.
FastCC is also supported on RVE, while GHC isn't since there is only one
avaiable register.
Differential Revision: https://reviews.llvm.org/D70401
R_RISCV_CALL/R_RISCV_CALL_PLT distinction is not necessary and
R_RISCV_CALL has been deprecated. Since https://reviews.llvm.org/D132530
`call foo` assembles to R_RISCV_CALL_PLT. The `@plt` suffix is not
useful and can be removed now (matching AArch64 and PowerPC).
GNU assembler assembles `call foo` to RISCV_CALL_PLT since 2022-09
(70f35d72ef04cd23771875c1661c9975044a749c).
Without this patch, unconditionally changing MO_CALL to MO_PLT could
create `jump .L1@plt, a0`, which is invalid in LLVM integrated assembler
and GNU assembler.
For `CSR_Interrupt`, we can generate the register list via a single
`sequence`.
For `CSR_XLEN_F32_Interrupt` and `CSR_XLEN_F64_Interrupt`, I don't
see the reason why we need to keep the order the same as how we used
to allocate registers (and we have changed the order in D146488), so
I fold them into one `sequence`.
There are some *.ll changes because of the order change.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D154837
This was part of the N extension which did not make it into
version 1.12 of the privilege specification.
Reviewed By: jrtc27
Differential Revision: https://reviews.llvm.org/D149308
Currently, we restore the return address register as the last restoring
instruction in the epilog. The next instruction is `ret` usually. It is
a use of return address register. In some microarchitectures, there is
load-to-use data hazard. To avoid the load-to-use data hazard, we could
separate the load instruction from its use as far as possible. In this
patch, we reverse the order of restoring callee-saved registers to
increase the distance of `load ra` and `ret` in the epilog.
Differential Revision: https://reviews.llvm.org/D113967
Regenerated using:
./llvm/utils/update_llc_test_checks.py -u llvm/test/CodeGen/RISCV/*.ll
This has added comments to spill-related instructions and added @plt to
some symbols.
Differential Revision: https://reviews.llvm.org/D92841
- Save/restore only registers that are used.
This includes Callee saved registers and Caller saved registers
(arguments and temporaries) for integer and FP registers.
- If there is a call in the interrupt handler, save/restore all
Caller saved registers (arguments and temporaries) and all FP registers.
- Emit special return instructions depending on "interrupt"
attribute type.
Based on initial patch by Zhaoshi Zheng.
Reviewers: asb
Reviewed By: asb
Subscribers: rkruppe, the_o, MartinMosbeck, brucehoult, rbar, johnrusso, simoncook, sabuasal, niosHD, kito-cheng, shiva0217, zzheng, edward-jones, mgrang, rogfer01, llvm-commits
Differential Revision: https://reviews.llvm.org/D48411
llvm-svn: 338047
