[COFF, ARM64] Reorder handling of aarch64 MSVC builtins

[dmajor]

Summary

In CodeGenFunction::EmitAArch64BuiltinExpr(), bulk move of all of the aarch64 MSVC-builtin cases to an earlier point in the function (the // Handle non-overloaded intrinsics first. switch block) in order to avoid an unreachable in GetNeonType(). The NEON type-overloading logic is not appropriate for the Windows builtins.

Fixes https://llvm.org/pr42775

[efriedma]

lib/CodeGen/CGBuiltin.cpp

8182 ↗

(On Diff #212181)

I'm a little concerned about the overall code structure here; even if moving the code for the MSVC builtins is enough to fix those builtins specifically, is it actually impossible to hit this "default"? If it is, can we convert it to an "unreachable"?

[dmajor]

lib/CodeGen/CGBuiltin.cpp

8182 ↗

(On Diff #212181)

I'm not sure if this question was directed to me... this was a drive-by patch from my end so I'm not familiar with what other types of builtins there might be.

I should probably mention that I'm hoping to get a fix merged to 9.0 in order to unblock Firefox. Unless someone can tell me that the unreachable is definitely safe, I'd worry about adding instability into the release branch. Perhaps the unreachable could be done in a separate commit only on 10.0 trunk where the tolerance for surprises is generally better.

[efriedma]

LGTM

lib/CodeGen/CGBuiltin.cpp

8182 ↗

(On Diff #212181)

It should be impossible to reach this normally, I think; any target-specific builtin which codegen supports should be handled earlier, and target-specific builtins only exist on the relevant target. The issue would just be a weird crash if you add a new builtin Builtins.def without code generation support, instead of a nicer "unsupported" error.

But I'm okay taking this as-is without trying to refactor the code to handle that gracefully, if we need this for 9.0.

cfe/trunk/lib/CodeGen/CGBuiltin.cpp

   case NEON::BI__builtin_neon_vduph_lane_f16: {
     return Builder.CreateExtractElement(Ops[0], EmitScalarExpr(E->getArg(1)),
                                         "vget_lane");
   }
   case NEON::BI__builtin_neon_vduph_laneq_f16: {
     return Builder.CreateExtractElement(Ops[0], EmitScalarExpr(E->getArg(1)),
                                         "vgetq_lane");
   }
+  case AArch64::BI_BitScanForward:
+  case AArch64::BI_BitScanForward64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_BitScanForward, E);
+  case AArch64::BI_BitScanReverse:
+  case AArch64::BI_BitScanReverse64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_BitScanReverse, E);
+  case AArch64::BI_InterlockedAnd64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd, E);
+  case AArch64::BI_InterlockedExchange64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange, E);
+  case AArch64::BI_InterlockedExchangeAdd64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd, E);
+  case AArch64::BI_InterlockedExchangeSub64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeSub, E);
+  case AArch64::BI_InterlockedOr64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr, E);
+  case AArch64::BI_InterlockedXor64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor, E);
+  case AArch64::BI_InterlockedDecrement64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement, E);
+  case AArch64::BI_InterlockedIncrement64:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement, E);
+  case AArch64::BI_InterlockedExchangeAdd8_acq:
+  case AArch64::BI_InterlockedExchangeAdd16_acq:
+  case AArch64::BI_InterlockedExchangeAdd_acq:
+  case AArch64::BI_InterlockedExchangeAdd64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd_acq, E);
+  case AArch64::BI_InterlockedExchangeAdd8_rel:
+  case AArch64::BI_InterlockedExchangeAdd16_rel:
+  case AArch64::BI_InterlockedExchangeAdd_rel:
+  case AArch64::BI_InterlockedExchangeAdd64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd_rel, E);
+  case AArch64::BI_InterlockedExchangeAdd8_nf:
+  case AArch64::BI_InterlockedExchangeAdd16_nf:
+  case AArch64::BI_InterlockedExchangeAdd_nf:
+  case AArch64::BI_InterlockedExchangeAdd64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd_nf, E);
+  case AArch64::BI_InterlockedExchange8_acq:
+  case AArch64::BI_InterlockedExchange16_acq:
+  case AArch64::BI_InterlockedExchange_acq:
+  case AArch64::BI_InterlockedExchange64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange_acq, E);
+  case AArch64::BI_InterlockedExchange8_rel:
+  case AArch64::BI_InterlockedExchange16_rel:
+  case AArch64::BI_InterlockedExchange_rel:
+  case AArch64::BI_InterlockedExchange64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange_rel, E);
+  case AArch64::BI_InterlockedExchange8_nf:
+  case AArch64::BI_InterlockedExchange16_nf:
+  case AArch64::BI_InterlockedExchange_nf:
+  case AArch64::BI_InterlockedExchange64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange_nf, E);
+  case AArch64::BI_InterlockedCompareExchange8_acq:
+  case AArch64::BI_InterlockedCompareExchange16_acq:
+  case AArch64::BI_InterlockedCompareExchange_acq:
+  case AArch64::BI_InterlockedCompareExchange64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedCompareExchange_acq, E);
+  case AArch64::BI_InterlockedCompareExchange8_rel:
+  case AArch64::BI_InterlockedCompareExchange16_rel:
+  case AArch64::BI_InterlockedCompareExchange_rel:
+  case AArch64::BI_InterlockedCompareExchange64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedCompareExchange_rel, E);
+  case AArch64::BI_InterlockedCompareExchange8_nf:
+  case AArch64::BI_InterlockedCompareExchange16_nf:
+  case AArch64::BI_InterlockedCompareExchange_nf:
+  case AArch64::BI_InterlockedCompareExchange64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedCompareExchange_nf, E);
+  case AArch64::BI_InterlockedOr8_acq:
+  case AArch64::BI_InterlockedOr16_acq:
+  case AArch64::BI_InterlockedOr_acq:
+  case AArch64::BI_InterlockedOr64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr_acq, E);
+  case AArch64::BI_InterlockedOr8_rel:
+  case AArch64::BI_InterlockedOr16_rel:
+  case AArch64::BI_InterlockedOr_rel:
+  case AArch64::BI_InterlockedOr64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr_rel, E);
+  case AArch64::BI_InterlockedOr8_nf:
+  case AArch64::BI_InterlockedOr16_nf:
+  case AArch64::BI_InterlockedOr_nf:
+  case AArch64::BI_InterlockedOr64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr_nf, E);
+  case AArch64::BI_InterlockedXor8_acq:
+  case AArch64::BI_InterlockedXor16_acq:
+  case AArch64::BI_InterlockedXor_acq:
+  case AArch64::BI_InterlockedXor64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor_acq, E);
+  case AArch64::BI_InterlockedXor8_rel:
+  case AArch64::BI_InterlockedXor16_rel:
+  case AArch64::BI_InterlockedXor_rel:
+  case AArch64::BI_InterlockedXor64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor_rel, E);
+  case AArch64::BI_InterlockedXor8_nf:
+  case AArch64::BI_InterlockedXor16_nf:
+  case AArch64::BI_InterlockedXor_nf:
+  case AArch64::BI_InterlockedXor64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor_nf, E);
+  case AArch64::BI_InterlockedAnd8_acq:
+  case AArch64::BI_InterlockedAnd16_acq:
+  case AArch64::BI_InterlockedAnd_acq:
+  case AArch64::BI_InterlockedAnd64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd_acq, E);
+  case AArch64::BI_InterlockedAnd8_rel:
+  case AArch64::BI_InterlockedAnd16_rel:
+  case AArch64::BI_InterlockedAnd_rel:
+  case AArch64::BI_InterlockedAnd64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd_rel, E);
+  case AArch64::BI_InterlockedAnd8_nf:
+  case AArch64::BI_InterlockedAnd16_nf:
+  case AArch64::BI_InterlockedAnd_nf:
+  case AArch64::BI_InterlockedAnd64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd_nf, E);
+  case AArch64::BI_InterlockedIncrement16_acq:
+  case AArch64::BI_InterlockedIncrement_acq:
+  case AArch64::BI_InterlockedIncrement64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement_acq, E);
+  case AArch64::BI_InterlockedIncrement16_rel:
+  case AArch64::BI_InterlockedIncrement_rel:
+  case AArch64::BI_InterlockedIncrement64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement_rel, E);
+  case AArch64::BI_InterlockedIncrement16_nf:
+  case AArch64::BI_InterlockedIncrement_nf:
+  case AArch64::BI_InterlockedIncrement64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement_nf, E);
+  case AArch64::BI_InterlockedDecrement16_acq:
+  case AArch64::BI_InterlockedDecrement_acq:
+  case AArch64::BI_InterlockedDecrement64_acq:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement_acq, E);
+  case AArch64::BI_InterlockedDecrement16_rel:
+  case AArch64::BI_InterlockedDecrement_rel:
+  case AArch64::BI_InterlockedDecrement64_rel:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement_rel, E);
+  case AArch64::BI_InterlockedDecrement16_nf:
+  case AArch64::BI_InterlockedDecrement_nf:
+  case AArch64::BI_InterlockedDecrement64_nf:
+    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement_nf, E);
+
+  case AArch64::BI_InterlockedAdd: {
+    Value *Arg0 = EmitScalarExpr(E->getArg(0));
+    Value *Arg1 = EmitScalarExpr(E->getArg(1));
+    AtomicRMWInst *RMWI = Builder.CreateAtomicRMW(
+      AtomicRMWInst::Add, Arg0, Arg1,
+      llvm::AtomicOrdering::SequentiallyConsistent);
+    return Builder.CreateAdd(RMWI, Arg1);
+  }
   }
 
   llvm::VectorType *VTy = GetNeonType(this, Type);
   llvm::Type *Ty = VTy;
   if (!Ty)
     return nullptr;
 
   // Not all intrinsics handled by the common case work for AArch64 yet, so only
case NEON::BI__builtin_neon_vsqaddq_v: {
     Int = Intrinsic::aarch64_neon_usqadd;
     return EmitNeonCall(CGM.getIntrinsic(Int, Ty), Ops, "vsqadd");
   }
   case NEON::BI__builtin_neon_vuqadd_v:
   case NEON::BI__builtin_neon_vuqaddq_v: {
     Int = Intrinsic::aarch64_neon_suqadd;
     return EmitNeonCall(CGM.getIntrinsic(Int, Ty), Ops, "vuqadd");
   }
-  case AArch64::BI_BitScanForward:
-  case AArch64::BI_BitScanForward64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_BitScanForward, E);
-  case AArch64::BI_BitScanReverse:
-  case AArch64::BI_BitScanReverse64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_BitScanReverse, E);
-  case AArch64::BI_InterlockedAnd64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd, E);
-  case AArch64::BI_InterlockedExchange64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange, E);
-  case AArch64::BI_InterlockedExchangeAdd64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd, E);
-  case AArch64::BI_InterlockedExchangeSub64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeSub, E);
-  case AArch64::BI_InterlockedOr64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr, E);
-  case AArch64::BI_InterlockedXor64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor, E);
-  case AArch64::BI_InterlockedDecrement64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement, E);
-  case AArch64::BI_InterlockedIncrement64:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement, E);
-  case AArch64::BI_InterlockedExchangeAdd8_acq:
-  case AArch64::BI_InterlockedExchangeAdd16_acq:
-  case AArch64::BI_InterlockedExchangeAdd_acq:
-  case AArch64::BI_InterlockedExchangeAdd64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd_acq, E);
-  case AArch64::BI_InterlockedExchangeAdd8_rel:
-  case AArch64::BI_InterlockedExchangeAdd16_rel:
-  case AArch64::BI_InterlockedExchangeAdd_rel:
-  case AArch64::BI_InterlockedExchangeAdd64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd_rel, E);
-  case AArch64::BI_InterlockedExchangeAdd8_nf:
-  case AArch64::BI_InterlockedExchangeAdd16_nf:
-  case AArch64::BI_InterlockedExchangeAdd_nf:
-  case AArch64::BI_InterlockedExchangeAdd64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchangeAdd_nf, E);
-  case AArch64::BI_InterlockedExchange8_acq:
-  case AArch64::BI_InterlockedExchange16_acq:
-  case AArch64::BI_InterlockedExchange_acq:
-  case AArch64::BI_InterlockedExchange64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange_acq, E);
-  case AArch64::BI_InterlockedExchange8_rel:
-  case AArch64::BI_InterlockedExchange16_rel:
-  case AArch64::BI_InterlockedExchange_rel:
-  case AArch64::BI_InterlockedExchange64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange_rel, E);
-  case AArch64::BI_InterlockedExchange8_nf:
-  case AArch64::BI_InterlockedExchange16_nf:
-  case AArch64::BI_InterlockedExchange_nf:
-  case AArch64::BI_InterlockedExchange64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedExchange_nf, E);
-  case AArch64::BI_InterlockedCompareExchange8_acq:
-  case AArch64::BI_InterlockedCompareExchange16_acq:
-  case AArch64::BI_InterlockedCompareExchange_acq:
-  case AArch64::BI_InterlockedCompareExchange64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedCompareExchange_acq, E);
-  case AArch64::BI_InterlockedCompareExchange8_rel:
-  case AArch64::BI_InterlockedCompareExchange16_rel:
-  case AArch64::BI_InterlockedCompareExchange_rel:
-  case AArch64::BI_InterlockedCompareExchange64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedCompareExchange_rel, E);
-  case AArch64::BI_InterlockedCompareExchange8_nf:
-  case AArch64::BI_InterlockedCompareExchange16_nf:
-  case AArch64::BI_InterlockedCompareExchange_nf:
-  case AArch64::BI_InterlockedCompareExchange64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedCompareExchange_nf, E);
-  case AArch64::BI_InterlockedOr8_acq:
-  case AArch64::BI_InterlockedOr16_acq:
-  case AArch64::BI_InterlockedOr_acq:
-  case AArch64::BI_InterlockedOr64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr_acq, E);
-  case AArch64::BI_InterlockedOr8_rel:
-  case AArch64::BI_InterlockedOr16_rel:
-  case AArch64::BI_InterlockedOr_rel:
-  case AArch64::BI_InterlockedOr64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr_rel, E);
-  case AArch64::BI_InterlockedOr8_nf:
-  case AArch64::BI_InterlockedOr16_nf:
-  case AArch64::BI_InterlockedOr_nf:
-  case AArch64::BI_InterlockedOr64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedOr_nf, E);
-  case AArch64::BI_InterlockedXor8_acq:
-  case AArch64::BI_InterlockedXor16_acq:
-  case AArch64::BI_InterlockedXor_acq:
-  case AArch64::BI_InterlockedXor64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor_acq, E);
-  case AArch64::BI_InterlockedXor8_rel:
-  case AArch64::BI_InterlockedXor16_rel:
-  case AArch64::BI_InterlockedXor_rel:
-  case AArch64::BI_InterlockedXor64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor_rel, E);
-  case AArch64::BI_InterlockedXor8_nf:
-  case AArch64::BI_InterlockedXor16_nf:
-  case AArch64::BI_InterlockedXor_nf:
-  case AArch64::BI_InterlockedXor64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedXor_nf, E);
-  case AArch64::BI_InterlockedAnd8_acq:
-  case AArch64::BI_InterlockedAnd16_acq:
-  case AArch64::BI_InterlockedAnd_acq:
-  case AArch64::BI_InterlockedAnd64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd_acq, E);
-  case AArch64::BI_InterlockedAnd8_rel:
-  case AArch64::BI_InterlockedAnd16_rel:
-  case AArch64::BI_InterlockedAnd_rel:
-  case AArch64::BI_InterlockedAnd64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd_rel, E);
-  case AArch64::BI_InterlockedAnd8_nf:
-  case AArch64::BI_InterlockedAnd16_nf:
-  case AArch64::BI_InterlockedAnd_nf:
-  case AArch64::BI_InterlockedAnd64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedAnd_nf, E);
-  case AArch64::BI_InterlockedIncrement16_acq:
-  case AArch64::BI_InterlockedIncrement_acq:
-  case AArch64::BI_InterlockedIncrement64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement_acq, E);
-  case AArch64::BI_InterlockedIncrement16_rel:
-  case AArch64::BI_InterlockedIncrement_rel:
-  case AArch64::BI_InterlockedIncrement64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement_rel, E);
-  case AArch64::BI_InterlockedIncrement16_nf:
-  case AArch64::BI_InterlockedIncrement_nf:
-  case AArch64::BI_InterlockedIncrement64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement_nf, E);
-  case AArch64::BI_InterlockedDecrement16_acq:
-  case AArch64::BI_InterlockedDecrement_acq:
-  case AArch64::BI_InterlockedDecrement64_acq:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement_acq, E);
-  case AArch64::BI_InterlockedDecrement16_rel:
-  case AArch64::BI_InterlockedDecrement_rel:
-  case AArch64::BI_InterlockedDecrement64_rel:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement_rel, E);
-  case AArch64::BI_InterlockedDecrement16_nf:
-  case AArch64::BI_InterlockedDecrement_nf:
-  case AArch64::BI_InterlockedDecrement64_nf:
-    return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement_nf, E);
-
-  case AArch64::BI_InterlockedAdd: {
-    Value *Arg0 = EmitScalarExpr(E->getArg(0));
-    Value *Arg1 = EmitScalarExpr(E->getArg(1));
-    AtomicRMWInst *RMWI = Builder.CreateAtomicRMW(
-      AtomicRMWInst::Add, Arg0, Arg1,
-      llvm::AtomicOrdering::SequentiallyConsistent);
-    return Builder.CreateAdd(RMWI, Arg1);
-  }
   }
 }
 
 llvm::Value *CodeGenFunction::
 BuildVector(ArrayRef<llvm::Value*> Ops) {
   assert((Ops.size() & (Ops.size() - 1)) == 0 &&
          "Not a power-of-two sized vector!");
   bool AllConstants = true;

cfe/trunk/test/CodeGen/arm64-microsoft-intrinsics.c

 // RUN: %clang_cc1 -triple arm64-windows -fms-compatibility -emit-llvm -o - %s \
 // RUN:    | FileCheck %s -check-prefix CHECK-MSVC
 
 // RUN: not %clang_cc1 -triple arm64-linux -Werror -S -o /dev/null %s 2>&1 \
 // RUN:    | FileCheck %s -check-prefix CHECK-LINUX
 
 long test_InterlockedAdd(long volatile *Addend, long Value) {
   return _InterlockedAdd(Addend, Value);
 }
 
+long test_InterlockedAdd_constant(long volatile *Addend) {
+  return _InterlockedAdd(Addend, -1);
+}
+
 // CHECK-LABEL: define {{.*}} i32 @test_InterlockedAdd(i32* %Addend, i32 %Value) {{.*}} {
 // CHECK-MSVC: %[[OLDVAL:[0-9]+]] = atomicrmw add i32* %1, i32 %2 seq_cst
 // CHECK-MSVC: %[[NEWVAL:[0-9]+]] = add i32 %[[OLDVAL:[0-9]+]], %2
 // CHECK-MSVC: ret i32 %[[NEWVAL:[0-9]+]]
 // CHECK-LINUX: error: implicit declaration of function '_InterlockedAdd'
 
 void check__dmb(void) {
   __dmb(0);