[clang-tools-extra] [llvm] [clang] Add out-of-line-atomics support to GlobalISel (PR #74588)

[Amara Emerson via llvm-commits]

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@@ -765,6 +766,138 @@ llvm::createMemLibcall(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
   return LegalizerHelper::Legalized;
 }
 
+static RTLIB::Libcall getOutlineAtomicLibcall(MachineInstr &MI) {
+  unsigned Opc = MI.getOpcode();
+  auto &AtomicMI = cast<GMemOperation>(MI);
+  auto &MMO = AtomicMI.getMMO();
+  auto Ordering = MMO.getMergedOrdering();
+  LLT MemType = MMO.getMemoryType();
+  uint64_t MemSize = MemType.getSizeInBytes();
+  if (!MemType.isScalar())
+    return RTLIB::UNKNOWN_LIBCALL;
+
+#define LCALLS(A, B)                                                           \
+  { A##B##_RELAX, A##B##_ACQ, A##B##_REL, A##B##_ACQ_REL }
+#define LCALL5(A)                                                              \
+  LCALLS(A, 1), LCALLS(A, 2), LCALLS(A, 4), LCALLS(A, 8), LCALLS(A, 16)
+  switch (Opc) {
+  case TargetOpcode::G_ATOMIC_CMPXCHG:
+  case TargetOpcode::G_ATOMIC_CMPXCHG_WITH_SUCCESS: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_CAS)};
+    return getOutlineAtomicHelper(LC, Ordering, MemSize);
+  }
+  case TargetOpcode::G_ATOMICRMW_XCHG: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_SWP)};
+    return getOutlineAtomicHelper(LC, Ordering, MemSize);
+  }
+  case TargetOpcode::G_ATOMICRMW_ADD:
+  case TargetOpcode::G_ATOMICRMW_SUB: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_LDADD)};
+    return getOutlineAtomicHelper(LC, Ordering, MemSize);
+  }
+  case TargetOpcode::G_ATOMICRMW_AND: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_LDCLR)};
+    return getOutlineAtomicHelper(LC, Ordering, MemSize);
+  }
+  case TargetOpcode::G_ATOMICRMW_OR: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_LDSET)};
+    return getOutlineAtomicHelper(LC, Ordering, MemSize);
+  }
+  case TargetOpcode::G_ATOMICRMW_XOR: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_LDEOR)};
+    return getOutlineAtomicHelper(LC, Ordering, MemSize);
+  }
+  default:
+    return RTLIB::UNKNOWN_LIBCALL;
+  }
+#undef LCALLS
+#undef LCALL5
+}
+
+static LegalizerHelper::LegalizeResult
+createAtomicLibcall(MachineIRBuilder &MIRBuilder, MachineInstr &MI) {
+  auto &Ctx = MIRBuilder.getMF().getFunction().getContext();
+  MachineRegisterInfo &MRI = *MIRBuilder.getMRI();
+
+  // Add all the args, except for the last which is an imm denoting 'tail'.
+  // const CallLowering::ArgInfo &Result,
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aemerson wrote:

stray comment

https://github.com/llvm/llvm-project/pull/74588