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

[Pavel Iliin via llvm-commits]

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@@ -765,6 +765,175 @@ llvm::createMemLibcall(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
   return LegalizerHelper::Legalized;
 }
 
+static RTLIB::Libcall
+getOutlineAtomicLibcall(unsigned Opc, AtomicOrdering Order, uint64_t MemSize) {
+  unsigned ModeN, ModelN;
+  switch (MemSize) {
+  case 1:
+    ModeN = 0;
+    break;
+  case 2:
+    ModeN = 1;
+    break;
+  case 4:
+    ModeN = 2;
+    break;
+  case 8:
+    ModeN = 3;
+    break;
+  case 16:
+    ModeN = 4;
+    break;
+  default:
+    return RTLIB::UNKNOWN_LIBCALL;
+  }
+
+  switch (Order) {
+  case AtomicOrdering::Monotonic:
+    ModelN = 0;
+    break;
+  case AtomicOrdering::Acquire:
+    ModelN = 1;
+    break;
+  case AtomicOrdering::Release:
+    ModelN = 2;
+    break;
+  case AtomicOrdering::AcquireRelease:
+  case AtomicOrdering::SequentiallyConsistent:
+    ModelN = 3;
+    break;
+  default:
+    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 LC[ModeN][ModelN];
+  }
+  case TargetOpcode::G_ATOMICRMW_XCHG: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_SWP)};
+    return LC[ModeN][ModelN];
+  }
+  case TargetOpcode::G_ATOMICRMW_ADD: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_LDADD)};
+    return LC[ModeN][ModelN];
+  }
+  case TargetOpcode::G_ATOMICRMW_SUB: {
+    const RTLIB::Libcall LC[5][4] = {LCALL5(RTLIB::OUTLINE_ATOMIC_LDADD)};
----------------
ilinpv wrote:

The same outline atomic as for G_ATOMICRMW_ADD, join these cases would be nice

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