[all-commits] [llvm/llvm-project] 2cc47d: [MC] Preserve target MCSubtargetInfo subclass in M...

[Alexander Richardson via All-commits]

  Branch: refs/heads/users/arichardson/mc-preserve-target-mcsubtargetinfo-subclass-in-mccontext
  Home:   https://github.com/llvm/llvm-project
  Commit: 2cc47d99a1e5c8151dbb88f832fef99c6efa7afe
      https://github.com/llvm/llvm-project/commit/2cc47d99a1e5c8151dbb88f832fef99c6efa7afe
  Author: Alex Richardson <alexrichardson at google.com>
  Date:   2026-09-29 (Tue, 29 Sep 2026)

  Changed paths:
    M llvm/include/llvm/MC/MCSubtargetInfo.h
    M llvm/lib/MC/MCContext.cpp
    M llvm/test/TableGen/HwModeBitSet.td
    M llvm/unittests/MC/TargetRegistry.cpp
    M llvm/utils/TableGen/SubtargetEmitter.cpp

  Log Message:
  -----------
  [MC] Preserve target MCSubtargetInfo subclass in MCContext::getSubtargetCopy

Previously, MCContext::getSubtargetCopy placement-constructed a base
MCSubtargetInfo instance instead of the TableGen-generated
<Target>GenMCSubtargetInfo subclass, resetting the vtable to
MCSubtargetInfo and losing target overrides such as getHwMode,
getHwModeSet, and resolveVariantSchedClass. As a result, any
MCTargetAsmParser::copySTI() call (for example when handling .option
arch on RISC-V) caused STI.getHwMode() to return 0 (DefaultMode).

Add a virtual MCSubtargetInfo::copyTo helper overridden by
<Target>GenMCSubtargetInfo so MCContext::getSubtargetCopy preserves the
target's MCSubtargetInfo vtable.

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