[RISCV][MC] Delete unnecessary code section align

[StephenFan]

Summary

Since RISCVELFTargetObjectFile does not inherit RISCVMCObjectFileInfo,
the alignment of code section is always 4 even if c extension was enabled.
If c extension was enabled, the nop instruction is 2 bytes, which will
make the assember to emit a code align fixup.

[MaskRay]

Err, multiple virtual inheritance is tricky. Anyway to avoid it?

[craig.topper]

Could we make the text segment alignment a member variable of MCObjectInfo instead of needing to use a virtual method in MCObjectInfo? Then we'd just need to assign that member from RISCVMCObjectInfo and
RISCVTargetObjectFile.

[StephenFan]

1. Add setTextSectionAlignment function to allow target set text section alignment
2. Set RISCV's text section alignment when initialize RISCVELFTargetObjectFile
3. Set RISCV's text section alignment when create RISCVMCObjectFileInfo

[StephenFan]

rebase

[craig.topper]

llvm/lib/Target/RISCV/RISCVSubtarget.cpp

22 ↗

(On Diff #439275)

This is the only change in this file. Is it needed?

llvm/lib/Target/RISCV/RISCVTargetObjectFile.h

13 ↗

(On Diff #439275)

There no changes to this file other than include, is it really needed here?

[StephenFan]

Remove header file.

[craig.topper]

LGTM

[MaskRay]

llvm/test/CodeGen/RISCV/unnecessary-code-align.ll

5

; CHECK:      Relocations [
; CHECK-NEXT: ]

[StephenFan]

Remove CHECK-NOT.

[MaskRay]

If this tests alignment, you probably want to check llvm-readelf -S -r output. -S for the Al column. -r is to check there is no relocation.

[StephenFan]

Check llvm-readelf -S -r instead of llvm-readobj -r.