[LoongArch] Port over minimal applyFixup from RISCV

[xen0n]

Summary

Many DebugInfo tests now pass with native builds.

[SixWeining]

Is this a WIP patch? Will you add some tests?

How about @wangleiat's opinion?

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp

80–81

Can these 2 lines be moved before line-79?

[xen0n]

address @SixWeining's review comments

[xen0n]

The patch is ready for review.

This may not need a dedicated test case, because before the change most if not all DebugInfo tests fail on native LoongArch builds, and this change (together with the parent change) fixes them.

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp

80–81

fixed

[wangleiat]

LGTM

[fhahn]

Is it possible to add a unit tests for this?

[wangleiat]

In D132323#3751307, @fhahn wrote:

Is it possible to add a unit tests for this?

Thanks for the reminder, test cases will be added in the subsequent complete implementation of applyFixup.

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp

 }
 
 void LoongArchAsmBackend::applyFixup(const MCAssembler &Asm,
                                      const MCFixup &Fixup,
                                      const MCValue &Target,
                                      MutableArrayRef<char> Data, uint64_t Value,
                                      bool IsResolved,
                                      const MCSubtargetInfo *STI) const {
-  // TODO: Apply the Value for given Fixup into the provided data fragment.
+  if (!Value)
+    return; // Doesn't change encoding.
+
+  MCFixupKind Kind = Fixup.getKind();
+  if (Kind >= FirstLiteralRelocationKind)
     return;
+  MCFixupKindInfo Info = getFixupKindInfo(Kind);
+  // TODO: Apply any target-specific value adjustments.
+
+  // Shift the value into position.
+  Value <<= Info.TargetOffset;
+
+  unsigned Offset = Fixup.getOffset();
+  unsigned NumBytes = alignTo(Info.TargetSize + Info.TargetOffset, 8) / 8;
+
+  assert(Offset + NumBytes <= Data.size() && "Invalid fixup offset!");
+  // For each byte of the fragment that the fixup touches, mask in the
+  // bits from the fixup value.
+  for (unsigned I = 0; I != NumBytes; ++I) {
+    Data[Offset + I] |= uint8_t((Value >> (I * 8)) & 0xff);
+  }
 }
 
 bool LoongArchAsmBackend::shouldForceRelocation(const MCAssembler &Asm,
                                                 const MCFixup &Fixup,
                                                 const MCValue &Target) {
   if (Fixup.getKind() >= FirstLiteralRelocationKind)
     return true;
   // TODO: Determine which relocation require special processing at linking