The SelectionDAG scheduling preference now becomes source order
scheduling (machine scheduler generates better code -- even without
there being a machine model defined for LoongArch yet).
Most of the test changes are trivial instruction reorderings and
differing register allocations, without any obvious performance impact.
This is similar to commit: 3d0fbafd0bce43bb9106230a45d1130f7a40e5ec
Some CPUs do not allow memory accesses to be unaligned, e.g. 2k1000la
who uses the la264 core on which misaligned access will trigger an
exception.
In this patch, a backend feature called `ual` is defined to decribe
whether the CPU supports unaligned memroy accesses. And this feature
can be toggled by clang options `-m[no-]unaligned-access` or the
aliases `-m[no-]strict-align`. When this feature is on,
`allowsMisalignedMemoryAccesses` sets the speed number to 1 and returns
true that allows the codegen to generate unaligned memory access insns.
Clang options `-m[no-]unaligned-access` are moved from `m_arm_Features_Group`
to `m_Group` because now more than one targets use them. And a test
is added to show that they remain unused on a target that does not
support them. In addition, to keep compatible with gcc, a new alias
`-mno-strict-align` is added which is equal to `-munaligned-access`.
The feature name `ual` is consistent with linux kernel [1] and the
output of `lscpu` or `/proc/cpuinfo` [2].
There is an `LLT` variant of `allowsMisalignedMemoryAccesses`, but
seems that curently it is only used in GlobalISel which LoongArch
doesn't support yet. So this variant is not implemented in this patch.
[1]: https://github.com/torvalds/linux/blob/master/arch/loongarch/include/asm/cpu.h#L77
[2]: https://github.com/torvalds/linux/blob/master/arch/loongarch/kernel/proc.c#L75
Reviewed By: xen0n
Differential Revision: https://reviews.llvm.org/D149946
This patch adds tail call support to the LoongArch backend. When
appropriate, use the `b` or `jr` instruction for tail calls (the
`pcalau12i+jirl` instruction pair when use medium codemodel).
This patch also modifies the inappropriate operand name:
simm26_bl -> simm26_symbol
This has been modeled after RISCV's tail call opt.
Reviewed By: SixWeining
Differential Revision: https://reviews.llvm.org/D137889
