[RISCV] Enable bidirectional scheduling and tracking register pressure (#115445)


This is based on other targets like PPC/AArch64 and some experiments.

This PR will only enable bidirectional schedu

[RISCV] Enable bidirectional scheduling and tracking register pressure (#115445)


This is based on other targets like PPC/AArch64 and some experiments.

This PR will only enable bidirectional scheduling and tracking register
pressure.

Disclaimer: I haven't tested it on many cores, maybe we should make
some options being features. I believe downstreams must have tried
this before, so feedbacks are welcome.

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[RISCV] Remove interrupt handler special case from RISCVFrameLowering::determineCalleeSaves. (#88069)

This code was trying to save temporary argument registers in interrupt
handler functions that c

[RISCV] Remove interrupt handler special case from RISCVFrameLowering::determineCalleeSaves. (#88069)

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

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[RISCV] Omit "@plt" in assembly output "call foo@plt" (#72467)

R_RISCV_CALL/R_RISCV_CALL_PLT distinction is not necessary and
R_RISCV_CALL has been deprecated. Since https://reviews.llvm.org/D132530

[RISCV] Omit "@plt" in assembly output "call foo@plt" (#72467)

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.

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[RISCV] Simplify the definitions of interrupt CSRs

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

[RISCV] Simplify the definitions of interrupt CSRs

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

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[RISCV] Move compressible registers to the beginning of the FP allocation order.

We don't have very many compressible FP instructions, just load and store.
These instruction require the FP register

[RISCV] Move compressible registers to the beginning of the FP allocation order.

We don't have very many compressible FP instructions, just load and store.
These instruction require the FP register to be f8-f15.

This patch changes the FP allocation order to prioritize f10-f15 first.
These are also the FP argument registers. So I allocated them in reverse
order starting at f15 to avoid taking the first argument registers.
This appears to match gcc allocation order.

Reviewed By: asb

Differential Revision: https://reviews.llvm.org/D146488

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[RISCV] Convert some tests to opaque pointers (NFC)

[RISCV] Reverse the order of loading/storing callee-saved registers.

Currently, we restore the return address register as the last restoring
instruction in the epilog. The next instruction is `ret`

[RISCV] Reverse the order of loading/storing callee-saved registers.

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

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[RISCV][NFC] Regenerate RISCV CodeGen tests

Regenerated using:

./llvm/utils/update_llc_test_checks.py -u llvm/test/CodeGen/RISCV/*.ll

This has added comments to spill-related instructions and adde

[RISCV][NFC] Regenerate RISCV CodeGen tests

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

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[RISCV] Fold ADDIs into load/stores with nonzero offsets

We can often fold an ADDI into the offset of load/store instructions:

(load (addi base, off1), off2) -> (load base, off1+off2)
(store

[RISCV] Fold ADDIs into load/stores with nonzero offsets

We can often fold an ADDI into the offset of load/store instructions:

(load (addi base, off1), off2) -> (load base, off1+off2)
(store val, (addi base, off1), off2) -> (store val, base, off1+off2)

This is possible when the off1+off2 continues to fit the 12-bit immediate.
We remove the previous restriction where we would never fold the ADDIs if
the load/stores had nonzero offsets. We now do the fold the the resulting
constant still fits a 12-bit immediate, or if off1 is a variable's address
and we know based on that variable's alignment that off1+offs2 won't overflow.

Differential Revision: https://reviews.llvm.org/D79690

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Migrate function attribute "no-frame-pointer-elim" to "frame-pointer"="all" as cleanups after D56351

[RISCV] Switch to the Machine Scheduler

Most of the test changes are trivial instruction reorderings and differing
register allocations, without any obvious performance impact.

Differential Revisio

[RISCV] Switch to the Machine Scheduler

Most of the test changes are trivial instruction reorderings and differing
register allocations, without any obvious performance impact.

Differential Revision: https://reviews.llvm.org/D66973

llvm-svn: 372106

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Revert Patch from Phabricator

This reverts r372092 (git commit e38695a0255c9e7b53639f349f8101bae1ce5c04)

llvm-svn: 372104

Patch from Phabricator

llvm-svn: 372092

[RISCV] Fix a couple of tests' CHECKs

llvm-svn: 370466

[RISCV][NFC] Add nounwind attribute to functions missing it in test/CodeGen/RISCV

This is in preparation for emitting CFI directives.

llvm-svn: 360897

[RISCV] Add support for _interrupt attribute

- Save/restore only registers that are used.
This includes Callee saved registers and Caller saved registers
(arguments and temporaries) for integer and

[RISCV] Add support for _interrupt attribute

- 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

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