[RISCV][CFI] add function epilogue cfi information (#110810)

This patch adds CFI instructions in the function epilogue.

Before patch:
addi sp, s0, -32
ld ra, 24(sp) # 8-byte Folded Reload
ld s

[RISCV][CFI] add function epilogue cfi information (#110810)

This patch adds CFI instructions in the function epilogue.

Before patch:
addi sp, s0, -32
ld ra, 24(sp) # 8-byte Folded Reload
ld s0, 16(sp) # 8-byte Folded Reload
ld s1, 8(sp) # 8-byte Folded Reload
addi sp, sp, 32
ret

After patch:
addi sp, s0, -32
.cfi_def_cfa sp, 32
ld ra, 24(sp) # 8-byte Folded Reload
ld s0, 16(sp) # 8-byte Folded Reload
ld s1, 8(sp) # 8-byte Folded Reload
.cfi_restore ra
.cfi_restore s0
.cfi_restore s1
addi sp, sp, 32
.cfi_def_cfa_offset 0
ret

This functionality is already present in `riscv-gcc`, but it’s not in
`clang` and this slightly impairs the `lldb` debugging experience, e.g.
backtrace.

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[RISCV] Don't cost Fmv for Zfinx in isFPImmLegal. (#107361)

There is no Fmv with Zfinx.

[RISCV] Use REG_SEQUENCE/EXTRACT_SUBREG to move between individual GPRs and GPRPair. (#85887)

Previously we used memory like we do to move between GPRs and FPR64 with
the D extension on RV32.

We

[RISCV] Use REG_SEQUENCE/EXTRACT_SUBREG to move between individual GPRs and GPRPair. (#85887)

Previously we used memory like we do to move between GPRs and FPR64 with
the D extension on RV32.

We can instead use REG_SEQUENCE/EXTRACT_SUBREG to inform register
allocation how to do the copy without memory.

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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][CodeGen] Support Zdinx on RV32 codegen

This patch was split from D122918 .

Co-Author: @StephenFan @liaolucy @realqhc

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.

[RISCV][CodeGen] Support Zdinx on RV32 codegen

This patch was split from D122918 .

Co-Author: @StephenFan @liaolucy @realqhc

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D149743

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[RISCV][CodeGen] Support Zdinx on RV64 codegen

This patch was split from D122918 . Co-Author: @liaolucy @realqhc

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D149665

[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] Inline scalar ceil/floor/trunc/rint/round/roundeven.

This avoids the call overhead as well as the the save/restore of
fflags and the snan handling in the libm function.

The save/restore of

[RISCV] Inline scalar ceil/floor/trunc/rint/round/roundeven.

This avoids the call overhead as well as the the save/restore of
fflags and the snan handling in the libm function.

The save/restore of fflags and snan handling are needed to be
correct for -ftrapping-math. I think we can ignore them in the
default environment.

The inline sequence will generate an invalid exception for nan
and an inexact exception if fractional bits are discarded.

I've used a custom inserter to explicitly create the control flow
around the float->int->float conversion.

We can probably avoid the final fsgnj after the conversion for
no signed zeros FMF, but I'll leave that for future work.

Note the comparison constant is slightly different than glibc uses.
They use 1<<53 for double, I'm using 1<<52. I believe either are valid.
Numbers >= 1<<52 can't have any fractional bits. It's ok to do the
float->int->float conversion on numbers between 1<<53 and 1<<52 since
they will all fit in 64. We only have a problem if the double can't fit
in i64

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D136508

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[RISCV] Implement isUsedByReturnOnly TargetLowering hook in order to tailcall more libcalls

Prior to this patch, libcalls inserted by the SelectionDAG legalizer
could never be tailcalled. The eligib

[RISCV] Implement isUsedByReturnOnly TargetLowering hook in order to tailcall more libcalls

Prior to this patch, libcalls inserted by the SelectionDAG legalizer
could never be tailcalled. The eligibility of libcalls for tail calling
is is partly determined by checking TargetLowering::isInTailCallPosition
and comparing the return type of the libcall and the calleer.
isInTailCallPosition in turn calls TargetLowering::isUsedByReturnOnly
(which always returns false if not implemented by the target).

This patch provides a minimal implementation of
TargetLowering::isUsedByReturnOnly - enough to support tail calling
libcalls on hard float ABIs. Soft-float ABIs are left for a follow on
patch. libcall-tail-calls.ll also shows missed opportunities to tail
call integer libcalls, but this is due to issues outside of
the isUsedByReturnOnly hook.

Differential Revision: https://reviews.llvm.org/D131087

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[RISCV] Add codegen coverage for ceil/floor/trunc/round/roundeven within FPR

Currently, all of these go to libcalls. A change to improve lowering is upcoming.

[RISCV] Use check-prefixes to reduce check lines

Reviewed By: frasercrmck

Differential Revision: https://reviews.llvm.org/D125083

[RISCV] Add DAG combine to fold (fp_to_int (ffloor X)) -> (fcvt X, rdn)

Similar for ceil, trunc, round, and roundeven. This allows us to use
static rounding modes to avoid a libcall.

This optimizat

[RISCV] Add DAG combine to fold (fp_to_int (ffloor X)) -> (fcvt X, rdn)

Similar for ceil, trunc, round, and roundeven. This allows us to use
static rounding modes to avoid a libcall.

This optimization is done for AArch64 as isel patterns.
RISCV doesn't have instructions for ceil/floor/trunc/round/roundeven
so the operations don't stick around until isel to enable a pattern
match. Thus I've implemented a DAG combine.

We only handle XLen types except i32 on RV64. i32 will be type
legalized to a RISCVISD node. All other types will be type legalized
to XLen and maintain the FP_TO_SINT/UINT ISD opcode.

Reviewed By: asb

Differential Revision: https://reviews.llvm.org/D116771

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