[WebAssembly] Support for a ternary atomic RMW instruction

[aheejin]

Summary

This adds support for a ternary atomic RMW instruction: cmpxchg.

[aheejin]

Turns out this is not currently able to make use of truncating/extending instructions when the 'success flag' of the LLVM IR cmpxchg instruction is used.

[aheejin]

Variable name change

[aheejin]

I think this CL can be reviewed as is. I will add an optimization for the success flag thing in another CL bc it is gonna be too long. So the problem I was talking about is, let's say we have these two test cases:

define i64 @cmpxchg_i8_i64_loaded_value(i8* %p, i64 %exp, i64 %new) {
  %exp_t = trunc i64 %exp to i8
  %new_t = trunc i64 %new to i8
  %pair = cmpxchg i8* %p, i8 %exp_t, i8 %new_t seq_cst seq_cst
  %old = extractvalue { i8, i1 } %pair, 0
  %e = zext i8 %old to i64
  ret i64 %e
}

define i1 @cmpxchg_i8_i64_success(i8* %p, i64 %exp, i64 %new) {
  %exp_t = trunc i64 %exp to i8
  %new_t = trunc i64 %new to i8
  %pair = cmpxchg i8* %p, i8 %exp_t, i8 %new_t seq_cst seq_cst
  %succ = extractvalue { i8, i1 } %pair, 1
  ret i1 %succ
}

So, in the LLVM IR (not wasm), unlike atomicrmw instruction, cmpxchg instruction returns a pair of { loaded value, success flag }. So it returns an additional 'success flag' which indicates whether the loaded value and the expected value matches. With this CL, the first function's compilation result is going to be

cmpxchg_i8_i64_loaded_value:
  .param    i32, i64, i64
  .result   i64
  i64.atomic.rmw8_u.cmpxchg  $push0=, 0($0), $1, $2
  return    $pop0

But for the second function (which is little contrived, because, usually the success flag is not gonna be returned from a function but likely to be used in a loop condition), this fails to make use of the i64.atomic.rmw8_u.cmpxchg instruction. It's gonna be something like

cmpxchg_i8_i64_success:
  .param    i32, i64, i64
  .result   i32
  i32.wrap/i64  $push6=, $1
  tee_local  $push5=, $3=, $pop6
  i32.wrap/i64  $push0=, $2
  i32.atomic.rmw8_u.cmpxchg  $push1=, 0($0), $pop5, $pop0
  i32.const  $push2=, 255
  i32.and   $push3=, $3, $pop2
  i32.eq    $push4=, $pop1, $pop3
  return    $pop4

which is suboptimal. (This only happens when truncation-extension exists.)

I think we need another set of patterns to optimize this. And in case we want to use both the loaded value and the success flag, which I guess is the most common case, we need another set of patterns for that as well. I'll add that in another CL separately.

[aheejin]

• Add a TODO

lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h

inline unsigned GetDefaultP2Align(unsigned Opcode) {
   case WebAssembly::ATOMIC_RMW8_U_XOR_I32:
   case WebAssembly::ATOMIC_RMW8_U_XOR_I32_S:
   case WebAssembly::ATOMIC_RMW8_U_XOR_I64:
   case WebAssembly::ATOMIC_RMW8_U_XOR_I64_S:
   case WebAssembly::ATOMIC_RMW8_U_XCHG_I32:
   case WebAssembly::ATOMIC_RMW8_U_XCHG_I32_S:
   case WebAssembly::ATOMIC_RMW8_U_XCHG_I64:
   case WebAssembly::ATOMIC_RMW8_U_XCHG_I64_S:
+  case WebAssembly::ATOMIC_RMW8_U_CMPXCHG_I32:
+  case WebAssembly::ATOMIC_RMW8_U_CMPXCHG_I32_S:
+  case WebAssembly::ATOMIC_RMW8_U_CMPXCHG_I64:
+  case WebAssembly::ATOMIC_RMW8_U_CMPXCHG_I64_S:
     return 0;
   case WebAssembly::LOAD16_S_I32:
   case WebAssembly::LOAD16_S_I32_S:
   case WebAssembly::LOAD16_U_I32:
   case WebAssembly::LOAD16_U_I32_S:
   case WebAssembly::LOAD16_S_I64:
   case WebAssembly::LOAD16_S_I64_S:
   case WebAssembly::LOAD16_U_I64:
inline unsigned GetDefaultP2Align(unsigned Opcode) {
   case WebAssembly::ATOMIC_RMW16_U_XOR_I32:
   case WebAssembly::ATOMIC_RMW16_U_XOR_I32_S:
   case WebAssembly::ATOMIC_RMW16_U_XOR_I64:
   case WebAssembly::ATOMIC_RMW16_U_XOR_I64_S:
   case WebAssembly::ATOMIC_RMW16_U_XCHG_I32:
   case WebAssembly::ATOMIC_RMW16_U_XCHG_I32_S:
   case WebAssembly::ATOMIC_RMW16_U_XCHG_I64:
   case WebAssembly::ATOMIC_RMW16_U_XCHG_I64_S:
+  case WebAssembly::ATOMIC_RMW16_U_CMPXCHG_I32:
+  case WebAssembly::ATOMIC_RMW16_U_CMPXCHG_I32_S:
+  case WebAssembly::ATOMIC_RMW16_U_CMPXCHG_I64:
+  case WebAssembly::ATOMIC_RMW16_U_CMPXCHG_I64_S:
     return 1;
   case WebAssembly::LOAD_I32:
   case WebAssembly::LOAD_I32_S:
   case WebAssembly::LOAD_F32:
   case WebAssembly::LOAD_F32_S:
   case WebAssembly::STORE_I32:
   case WebAssembly::STORE_I32_S:
   case WebAssembly::STORE_F32:
inline unsigned GetDefaultP2Align(unsigned Opcode) {
   case WebAssembly::ATOMIC_RMW_XOR_I32:
   case WebAssembly::ATOMIC_RMW_XOR_I32_S:
   case WebAssembly::ATOMIC_RMW32_U_XOR_I64:
   case WebAssembly::ATOMIC_RMW32_U_XOR_I64_S:
   case WebAssembly::ATOMIC_RMW_XCHG_I32:
   case WebAssembly::ATOMIC_RMW_XCHG_I32_S:
   case WebAssembly::ATOMIC_RMW32_U_XCHG_I64:
   case WebAssembly::ATOMIC_RMW32_U_XCHG_I64_S:
+  case WebAssembly::ATOMIC_RMW_CMPXCHG_I32:
+  case WebAssembly::ATOMIC_RMW_CMPXCHG_I32_S:
+  case WebAssembly::ATOMIC_RMW32_U_CMPXCHG_I64:
+  case WebAssembly::ATOMIC_RMW32_U_CMPXCHG_I64_S:
     return 2;
   case WebAssembly::LOAD_I64:
   case WebAssembly::LOAD_I64_S:
   case WebAssembly::LOAD_F64:
   case WebAssembly::LOAD_F64_S:
   case WebAssembly::STORE_I64:
   case WebAssembly::STORE_I64_S:
   case WebAssembly::STORE_F64:
inline unsigned GetDefaultP2Align(unsigned Opcode) {
   case WebAssembly::ATOMIC_RMW_AND_I64:
   case WebAssembly::ATOMIC_RMW_AND_I64_S:
   case WebAssembly::ATOMIC_RMW_OR_I64:
   case WebAssembly::ATOMIC_RMW_OR_I64_S:
   case WebAssembly::ATOMIC_RMW_XOR_I64:
   case WebAssembly::ATOMIC_RMW_XOR_I64_S:
   case WebAssembly::ATOMIC_RMW_XCHG_I64:
   case WebAssembly::ATOMIC_RMW_XCHG_I64_S:
+  case WebAssembly::ATOMIC_RMW_CMPXCHG_I64:
+  case WebAssembly::ATOMIC_RMW_CMPXCHG_I64_S:
     return 3;
   default:
     llvm_unreachable("Only loads and stores have p2align values");
   }
 }
 
 /// The operand number of the load or store address in load/store instructions.
 static const unsigned LoadAddressOperandNo = 3;

lib/Target/WebAssembly/WebAssemblyInstrAtomics.td

defm : BinRMWTruncExtPattern<
   atomic_load_xor_8, atomic_load_xor_16, atomic_load_xor_32, atomic_load_xor_64,
   ATOMIC_RMW8_U_XOR_I32, ATOMIC_RMW16_U_XOR_I32,
   ATOMIC_RMW8_U_XOR_I64, ATOMIC_RMW16_U_XOR_I64, ATOMIC_RMW32_U_XOR_I64>;
 defm : BinRMWTruncExtPattern<
   atomic_swap_8, atomic_swap_16, atomic_swap_32, atomic_swap_64,
   ATOMIC_RMW8_U_XCHG_I32, ATOMIC_RMW16_U_XCHG_I32,
   ATOMIC_RMW8_U_XCHG_I64, ATOMIC_RMW16_U_XCHG_I64, ATOMIC_RMW32_U_XCHG_I64>;
 } // Predicates = [HasAtomics]
+
+//===----------------------------------------------------------------------===//
+// Atomic ternary read-modify-writes
+//===----------------------------------------------------------------------===//
+
+let Defs = [ARGUMENTS] in {
+
+multiclass WebAssemblyTerRMW<WebAssemblyRegClass rc, string Name, int Opcode> {
+  defm "" : I<(outs rc:$dst),
+              (ins P2Align:$p2align, offset32_op:$off, I32:$addr, rc:$exp,
+                   rc:$rep),
+              (outs), (ins P2Align:$p2align, offset32_op:$off), [],
+              !strconcat(Name, "\t$dst, ${off}(${addr})${p2align}, $exp, $rep"),
+              !strconcat(Name, "\t${off}, ${p2align}"), Opcode>;
+}
+
+defm ATOMIC_RMW_CMPXCHG_I32 :
+  WebAssemblyTerRMW<I32, "i32.atomic.rmw.cmpxchg", 0xfe48>;
+defm ATOMIC_RMW_CMPXCHG_I64 :
+  WebAssemblyTerRMW<I64, "i64.atomic.rmw.cmpxchg", 0xfe49>;
+defm ATOMIC_RMW8_U_CMPXCHG_I32 :
+  WebAssemblyTerRMW<I32, "i32.atomic.rmw8_u.cmpxchg", 0xfe4a>;
+defm ATOMIC_RMW16_U_CMPXCHG_I32 :
+  WebAssemblyTerRMW<I32, "i32.atomic.rmw16_u.cmpxchg", 0xfe4b>;
+defm ATOMIC_RMW8_U_CMPXCHG_I64 :
+  WebAssemblyTerRMW<I64, "i64.atomic.rmw8_u.cmpxchg", 0xfe4c>;
+defm ATOMIC_RMW16_U_CMPXCHG_I64 :
+  WebAssemblyTerRMW<I64, "i64.atomic.rmw16_u.cmpxchg", 0xfe4d>;
+defm ATOMIC_RMW32_U_CMPXCHG_I64 :
+  WebAssemblyTerRMW<I64, "i64.atomic.rmw32_u.cmpxchg", 0xfe4e>;
+}
+
+// Select ternary RMWs with no constant offset.
+class TerRMWPatNoOffset<ValueType ty, PatFrag kind, NI inst> :
+  Pat<(ty (kind I32:$addr, ty:$exp, ty:$rep)),
+      (inst 0, 0, I32:$addr, ty:$exp, ty:$rep)>;
+
+// Select ternary RMWs with a constant offset.
+
+// Pattern with address + immediate offset
+class TerRMWPatImmOff<ValueType ty, PatFrag kind, PatFrag operand, NI inst> :
+  Pat<(ty (kind (operand I32:$addr, imm:$off), ty:$exp, ty:$rep)),
+      (inst 0, imm:$off, I32:$addr, ty:$exp, ty:$rep)>;
+
+class TerRMWPatGlobalAddr<ValueType ty, PatFrag kind, NI inst> :
+  Pat<(ty (kind (regPlusGA I32:$addr, (WebAssemblywrapper tglobaladdr:$off)),
+                ty:$exp, ty:$rep)),
+      (inst 0, tglobaladdr:$off, I32:$addr, ty:$exp, ty:$rep)>;
+
+class TerRMWPatExternalSym<ValueType ty, PatFrag kind, NI inst> :
+  Pat<(ty (kind (add I32:$addr, (WebAssemblywrapper texternalsym:$off)),
+                ty:$exp, ty:$rep)),
+      (inst 0, texternalsym:$off, I32:$addr, ty:$exp, ty:$rep)>;
+
+// Select ternary RMWs with just a constant offset.
+class TerRMWPatOffsetOnly<ValueType ty, PatFrag kind, NI inst> :
+  Pat<(ty (kind imm:$off, ty:$exp, ty:$rep)),
+      (inst 0, imm:$off, (CONST_I32 0), ty:$exp, ty:$rep)>;
+
+class TerRMWPatGlobalAddrOffOnly<ValueType ty, PatFrag kind, NI inst> :
+  Pat<(ty (kind (WebAssemblywrapper tglobaladdr:$off), ty:$exp, ty:$rep)),
+      (inst 0, tglobaladdr:$off, (CONST_I32 0), ty:$exp, ty:$rep)>;
+
+class TerRMWPatExternSymOffOnly<ValueType ty, PatFrag kind, NI inst> :
+  Pat<(ty (kind (WebAssemblywrapper texternalsym:$off), ty:$exp, ty:$rep)),
+      (inst 0, texternalsym:$off, (CONST_I32 0), ty:$exp, ty:$rep)>;
+
+// Patterns for various addressing modes.
+multiclass TerRMWPattern<PatFrag rmw_32, PatFrag rmw_64, NI inst_32,
+                         NI inst_64> {
+  def : TerRMWPatNoOffset<i32, rmw_32, inst_32>;
+  def : TerRMWPatNoOffset<i64, rmw_64, inst_64>;
+
+  def : TerRMWPatImmOff<i32, rmw_32, regPlusImm, inst_32>;
+  def : TerRMWPatImmOff<i64, rmw_64, regPlusImm, inst_64>;
+  def : TerRMWPatImmOff<i32, rmw_32, or_is_add, inst_32>;
+  def : TerRMWPatImmOff<i64, rmw_64, or_is_add, inst_64>;
+
+  def : TerRMWPatGlobalAddr<i32, rmw_32, inst_32>;
+  def : TerRMWPatGlobalAddr<i64, rmw_64, inst_64>;
+
+  def : TerRMWPatExternalSym<i32, rmw_32, inst_32>;
+  def : TerRMWPatExternalSym<i64, rmw_64, inst_64>;
+
+  def : TerRMWPatOffsetOnly<i32, rmw_32, inst_32>;
+  def : TerRMWPatOffsetOnly<i64, rmw_64, inst_64>;
+
+  def : TerRMWPatGlobalAddrOffOnly<i32, rmw_32, inst_32>;
+  def : TerRMWPatGlobalAddrOffOnly<i64, rmw_64, inst_64>;
+
+  def : TerRMWPatExternSymOffOnly<i32, rmw_32, inst_32>;
+  def : TerRMWPatExternSymOffOnly<i64, rmw_64, inst_64>;
+}
+
+let Predicates = [HasAtomics] in {
+defm : TerRMWPattern<atomic_cmp_swap_32, atomic_cmp_swap_64,
+                     ATOMIC_RMW_CMPXCHG_I32, ATOMIC_RMW_CMPXCHG_I64>;
+} // Predicates = [HasAtomics]
+
+// Truncating & zero-extending ternary RMW patterns.
+// DAG legalization & optimization before instruction selection may introduce
+// additional nodes such as anyext or assertzext depending on operand types.
+class zext_ter_rmw_8_32<PatFrag kind> :
+  PatFrag<(ops node:$addr, node:$exp, node:$rep),
+          (and (i32 (kind node:$addr, node:$exp, node:$rep)), 255)>;
+class zext_ter_rmw_16_32<PatFrag kind> :
+  PatFrag<(ops node:$addr, node:$exp, node:$rep),
+          (and (i32 (kind node:$addr, node:$exp, node:$rep)), 65535)>;
+class zext_ter_rmw_8_64<PatFrag kind> :
+  PatFrag<(ops node:$addr, node:$exp, node:$rep),
+          (zext (i32 (assertzext (i32 (kind node:$addr,
+                                            (i32 (trunc (i64 node:$exp))),
+                                            (i32 (trunc (i64 node:$rep))))))))>;
+class zext_ter_rmw_16_64<PatFrag kind> : zext_ter_rmw_8_64<kind>;
+class zext_ter_rmw_32_64<PatFrag kind> :
+  PatFrag<(ops node:$addr, node:$exp, node:$rep),
+          (zext (i32 (kind node:$addr,
+                           (i32 (trunc (i64 node:$exp))),
+                           (i32 (trunc (i64 node:$rep))))))>;
+
+// Truncating & sign-extending ternary RMW patterns.
+// We match subword RMWs (for 32-bit) and anyext RMWs (for 64-bit) and select a
+// zext RMW; the next instruction will be sext_inreg which is selected by
+// itself.
+class sext_ter_rmw_8_32<PatFrag kind> :
+  PatFrag<(ops node:$addr, node:$exp, node:$rep),
+          (kind node:$addr, node:$exp, node:$rep)>;
+class sext_ter_rmw_16_32<PatFrag kind> : sext_ter_rmw_8_32<kind>;
+class sext_ter_rmw_8_64<PatFrag kind> :
+  PatFrag<(ops node:$addr, node:$exp, node:$rep),
+          (anyext (i32 (assertzext (i32
+            (kind node:$addr,
+                  (i32 (trunc (i64 node:$exp))),
+                  (i32 (trunc (i64 node:$rep))))))))>;
+class sext_ter_rmw_16_64<PatFrag kind> : sext_ter_rmw_8_64<kind>;
+// 32->64 sext RMW gets selected as i32.atomic.rmw.***, i64.extend_s/i32
+
+// Patterns for various addressing modes for truncating-extending ternary RMWs.
+multiclass TerRMWTruncExtPattern<
+  PatFrag rmw_8, PatFrag rmw_16, PatFrag rmw_32, PatFrag rmw_64,
+  NI inst8_32, NI inst16_32, NI inst8_64, NI inst16_64, NI inst32_64> {
+  // Truncating-extending ternary RMWs with no constant offset
+  def : TerRMWPatNoOffset<i32, zext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatNoOffset<i32, zext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatNoOffset<i64, zext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatNoOffset<i64, zext_ter_rmw_16_64<rmw_16>, inst16_64>;
+  def : TerRMWPatNoOffset<i64, zext_ter_rmw_32_64<rmw_32>, inst32_64>;
+
+  def : TerRMWPatNoOffset<i32, sext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatNoOffset<i32, sext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatNoOffset<i64, sext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatNoOffset<i64, sext_ter_rmw_16_64<rmw_16>, inst16_64>;
+
+  // Truncating-extending ternary RMWs with a constant offset
+  def : TerRMWPatImmOff<i32, zext_ter_rmw_8_32<rmw_8>, regPlusImm, inst8_32>;
+  def : TerRMWPatImmOff<i32, zext_ter_rmw_16_32<rmw_16>, regPlusImm, inst16_32>;
+  def : TerRMWPatImmOff<i64, zext_ter_rmw_8_64<rmw_8>, regPlusImm, inst8_64>;
+  def : TerRMWPatImmOff<i64, zext_ter_rmw_16_64<rmw_16>, regPlusImm, inst16_64>;
+  def : TerRMWPatImmOff<i64, zext_ter_rmw_32_64<rmw_32>, regPlusImm, inst32_64>;
+  def : TerRMWPatImmOff<i32, zext_ter_rmw_8_32<rmw_8>, or_is_add, inst8_32>;
+  def : TerRMWPatImmOff<i32, zext_ter_rmw_16_32<rmw_16>, or_is_add, inst16_32>;
+  def : TerRMWPatImmOff<i64, zext_ter_rmw_8_64<rmw_8>, or_is_add, inst8_64>;
+  def : TerRMWPatImmOff<i64, zext_ter_rmw_16_64<rmw_16>, or_is_add, inst16_64>;
+  def : TerRMWPatImmOff<i64, zext_ter_rmw_32_64<rmw_32>, or_is_add, inst32_64>;
+
+  def : TerRMWPatImmOff<i32, sext_ter_rmw_8_32<rmw_8>, regPlusImm, inst8_32>;
+  def : TerRMWPatImmOff<i32, sext_ter_rmw_16_32<rmw_16>, regPlusImm, inst16_32>;
+  def : TerRMWPatImmOff<i64, sext_ter_rmw_8_64<rmw_8>, regPlusImm, inst8_64>;
+  def : TerRMWPatImmOff<i64, sext_ter_rmw_16_64<rmw_16>, regPlusImm, inst16_64>;
+  def : TerRMWPatImmOff<i32, sext_ter_rmw_8_32<rmw_8>, or_is_add, inst8_32>;
+  def : TerRMWPatImmOff<i32, sext_ter_rmw_16_32<rmw_16>, or_is_add, inst16_32>;
+  def : TerRMWPatImmOff<i64, sext_ter_rmw_8_64<rmw_8>, or_is_add, inst8_64>;
+  def : TerRMWPatImmOff<i64, sext_ter_rmw_16_64<rmw_16>, or_is_add, inst16_64>;
+
+  def : TerRMWPatGlobalAddr<i32, zext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatGlobalAddr<i32, zext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatGlobalAddr<i64, zext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatGlobalAddr<i64, zext_ter_rmw_16_64<rmw_16>, inst16_64>;
+  def : TerRMWPatGlobalAddr<i64, zext_ter_rmw_32_64<rmw_32>, inst32_64>;
+
+  def : TerRMWPatGlobalAddr<i32, sext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatGlobalAddr<i32, sext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatGlobalAddr<i64, sext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatGlobalAddr<i64, sext_ter_rmw_16_64<rmw_16>, inst16_64>;
+
+  def : TerRMWPatExternalSym<i32, zext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatExternalSym<i32, zext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatExternalSym<i64, zext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatExternalSym<i64, zext_ter_rmw_16_64<rmw_16>, inst16_64>;
+  def : TerRMWPatExternalSym<i64, zext_ter_rmw_32_64<rmw_32>, inst32_64>;
+
+  def : TerRMWPatExternalSym<i32, sext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatExternalSym<i32, sext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatExternalSym<i64, sext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatExternalSym<i64, sext_ter_rmw_16_64<rmw_16>, inst16_64>;
+
+  // Truncating-extending ternary RMWs with just a constant offset
+  def : TerRMWPatOffsetOnly<i32, zext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatOffsetOnly<i32, zext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatOffsetOnly<i64, zext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatOffsetOnly<i64, zext_ter_rmw_16_64<rmw_16>, inst16_64>;
+  def : TerRMWPatOffsetOnly<i64, zext_ter_rmw_32_64<rmw_32>, inst32_64>;
+
+  def : TerRMWPatOffsetOnly<i32, sext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatOffsetOnly<i32, sext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatOffsetOnly<i64, sext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatOffsetOnly<i64, sext_ter_rmw_16_64<rmw_16>, inst16_64>;
+
+  def : TerRMWPatGlobalAddrOffOnly<i32, zext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatGlobalAddrOffOnly<i32, zext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatGlobalAddrOffOnly<i64, zext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatGlobalAddrOffOnly<i64, zext_ter_rmw_16_64<rmw_16>, inst16_64>;
+  def : TerRMWPatGlobalAddrOffOnly<i64, zext_ter_rmw_32_64<rmw_32>, inst32_64>;
+
+  def : TerRMWPatGlobalAddrOffOnly<i32, sext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatGlobalAddrOffOnly<i32, sext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatGlobalAddrOffOnly<i64, sext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatGlobalAddrOffOnly<i64, sext_ter_rmw_16_64<rmw_16>, inst16_64>;
+
+  def : TerRMWPatExternSymOffOnly<i32, zext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatExternSymOffOnly<i32, zext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatExternSymOffOnly<i64, zext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatExternSymOffOnly<i64, zext_ter_rmw_16_64<rmw_16>, inst16_64>;
+  def : TerRMWPatExternSymOffOnly<i64, zext_ter_rmw_32_64<rmw_32>, inst32_64>;
+
+  def : TerRMWPatExternSymOffOnly<i32, sext_ter_rmw_8_32<rmw_8>, inst8_32>;
+  def : TerRMWPatExternSymOffOnly<i32, sext_ter_rmw_16_32<rmw_16>, inst16_32>;
+  def : TerRMWPatExternSymOffOnly<i64, sext_ter_rmw_8_64<rmw_8>, inst8_64>;
+  def : TerRMWPatExternSymOffOnly<i64, sext_ter_rmw_16_64<rmw_16>, inst16_64>;
+}
+
+let Predicates = [HasAtomics] in {
+defm : TerRMWTruncExtPattern<
+  atomic_cmp_swap_8, atomic_cmp_swap_16, atomic_cmp_swap_32, atomic_cmp_swap_64,
+  ATOMIC_RMW8_U_CMPXCHG_I32, ATOMIC_RMW16_U_CMPXCHG_I32,
+  ATOMIC_RMW8_U_CMPXCHG_I64, ATOMIC_RMW16_U_CMPXCHG_I64,
+  ATOMIC_RMW32_U_CMPXCHG_I64>;
+} // Predicates = [HasAtomics]

lib/Target/WebAssembly/WebAssemblySetP2AlignOperands.cpp

for (auto &MI : MBB) {
       case WebAssembly::ATOMIC_RMW8_U_AND_I32:
       case WebAssembly::ATOMIC_RMW8_U_AND_I64:
       case WebAssembly::ATOMIC_RMW8_U_OR_I32:
       case WebAssembly::ATOMIC_RMW8_U_OR_I64:
       case WebAssembly::ATOMIC_RMW8_U_XOR_I32:
       case WebAssembly::ATOMIC_RMW8_U_XOR_I64:
       case WebAssembly::ATOMIC_RMW8_U_XCHG_I32:
       case WebAssembly::ATOMIC_RMW8_U_XCHG_I64:
+      case WebAssembly::ATOMIC_RMW8_U_CMPXCHG_I32:
+      case WebAssembly::ATOMIC_RMW8_U_CMPXCHG_I64:
       case WebAssembly::ATOMIC_RMW16_U_ADD_I32:
       case WebAssembly::ATOMIC_RMW16_U_ADD_I64:
       case WebAssembly::ATOMIC_RMW16_U_SUB_I32:
       case WebAssembly::ATOMIC_RMW16_U_SUB_I64:
       case WebAssembly::ATOMIC_RMW16_U_AND_I32:
       case WebAssembly::ATOMIC_RMW16_U_AND_I64:
       case WebAssembly::ATOMIC_RMW16_U_OR_I32:
       case WebAssembly::ATOMIC_RMW16_U_OR_I64:
       case WebAssembly::ATOMIC_RMW16_U_XOR_I32:
       case WebAssembly::ATOMIC_RMW16_U_XOR_I64:
       case WebAssembly::ATOMIC_RMW16_U_XCHG_I32:
       case WebAssembly::ATOMIC_RMW16_U_XCHG_I64:
+      case WebAssembly::ATOMIC_RMW16_U_CMPXCHG_I32:
+      case WebAssembly::ATOMIC_RMW16_U_CMPXCHG_I64:
       case WebAssembly::ATOMIC_RMW_ADD_I32:
       case WebAssembly::ATOMIC_RMW32_U_ADD_I64:
       case WebAssembly::ATOMIC_RMW_SUB_I32:
       case WebAssembly::ATOMIC_RMW32_U_SUB_I64:
       case WebAssembly::ATOMIC_RMW_AND_I32:
       case WebAssembly::ATOMIC_RMW32_U_AND_I64:
       case WebAssembly::ATOMIC_RMW_OR_I32:
       case WebAssembly::ATOMIC_RMW32_U_OR_I64:
       case WebAssembly::ATOMIC_RMW_XOR_I32:
       case WebAssembly::ATOMIC_RMW32_U_XOR_I64:
       case WebAssembly::ATOMIC_RMW_XCHG_I32:
       case WebAssembly::ATOMIC_RMW32_U_XCHG_I64:
+      case WebAssembly::ATOMIC_RMW_CMPXCHG_I32:
+      case WebAssembly::ATOMIC_RMW32_U_CMPXCHG_I64:
       case WebAssembly::ATOMIC_RMW_ADD_I64:
       case WebAssembly::ATOMIC_RMW_SUB_I64:
       case WebAssembly::ATOMIC_RMW_AND_I64:
       case WebAssembly::ATOMIC_RMW_OR_I64:
       case WebAssembly::ATOMIC_RMW_XOR_I64:
       case WebAssembly::ATOMIC_RMW_XCHG_I64:
+      case WebAssembly::ATOMIC_RMW_CMPXCHG_I64:
         RewriteP2Align(MI, WebAssembly::LoadP2AlignOperandNo);
         break;
       case WebAssembly::STORE_I32:
       case WebAssembly::STORE_I64:
       case WebAssembly::STORE_F32:
       case WebAssembly::STORE_F64:
       case WebAssembly::STORE8_I32:
       case WebAssembly::STORE16_I32:

test/CodeGen/WebAssembly/atomic-mem-consistency.ll

 ; CHECK-LABEL: add_i32_seq_cst:
 ; CHECK-NEXT: .param i32, i32{{$}}
 ; CHECK: i32.atomic.rmw.add $push0=, 0($0), $1{{$}}
 ; CHECK-NEXT: return $pop0{{$}}
 define i32 @add_i32_seq_cst(i32* %p, i32 %v) {
   %old = atomicrmw add i32* %p, i32 %v seq_cst
   ret i32 %old
 }
+
+; Ternary RMW instruction: cmpxchg
+; The success and failure ordering arguments specify how this cmpxchg
+; synchronizes with other atomic operations. Both ordering parameters must be at
+; least monotonic, the ordering constraint on failure must be no stronger than
+; that on success, and the failure ordering cannot be either release or acq_rel.
+
+; CHECK-LABEL: cmpxchg_i32_monotonic_monotonic:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_monotonic_monotonic(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new monotonic monotonic
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_acquire_monotonic:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_acquire_monotonic(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new acquire monotonic
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_release_monotonic:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_release_monotonic(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new release monotonic
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_acq_rel_monotonic:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_acq_rel_monotonic(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new acq_rel monotonic
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_seq_cst_monotonic:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_seq_cst_monotonic(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new seq_cst monotonic
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_acquire_acquire:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_acquire_acquire(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new acquire acquire
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_release_acquire:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_release_acquire(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new release acquire
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_acq_rel_acquire:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_acq_rel_acquire(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new acq_rel acquire
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_seq_cst_acquire:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_seq_cst_acquire(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new seq_cst acquire
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_seq_cst_seq_cst:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_seq_cst_seq_cst(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}

test/CodeGen/WebAssembly/atomic-rmw.ll

 ; CHECK-NEXT: .param i32, i32{{$}}
 ; CHECK: i32.atomic.rmw.xchg $push0=, 0($0), $1{{$}}
 ; CHECK-NEXT: return $pop0{{$}}
 define i32 @xchg_i32(i32* %p, i32 %v) {
   %old = atomicrmw xchg i32* %p, i32 %v seq_cst
   ret i32 %old
 }
 
+; CHECK-LABEL: cmpxchg_i32_loaded_value:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_loaded_value(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_success:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: i32.eq $push1=, $pop0, $1{{$}}
+; CHECK-NEXT: return $pop1{{$}}
+define i1 @cmpxchg_i32_success(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new seq_cst seq_cst
+  %succ = extractvalue { i32, i1 } %pair, 1
+  ret i1 %succ
+}
+
 ;===----------------------------------------------------------------------------
 ; Atomic read-modify-writes: 64-bit
 ;===----------------------------------------------------------------------------
 
 ; CHECK-LABEL: add_i64:
 ; CHECK-NEXT: .param i32, i64{{$}}
 ; CHECK: i64.atomic.rmw.add $push0=, 0($0), $1{{$}}
 ; CHECK-NEXT: return $pop0{{$}}

 ; CHECK-NEXT: .param i32, i64{{$}}
 ; CHECK: i64.atomic.rmw.xchg $push0=, 0($0), $1{{$}}
 ; CHECK-NEXT: return $pop0{{$}}
 define i64 @xchg_i64(i64* %p, i64 %v) {
   %old = atomicrmw xchg i64* %p, i64 %v seq_cst
   ret i64 %old
 }
 
+; CHECK-LABEL: cmpxchg_i64_loaded_value:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i64 @cmpxchg_i64_loaded_value(i64* %p, i64 %exp, i64 %new) {
+  %pair = cmpxchg i64* %p, i64 %exp, i64 %new seq_cst seq_cst
+  %old = extractvalue { i64, i1 } %pair, 0
+  ret i64 %old
+}
+
+; CHECK-LABEL: cmpxchg_i64_success:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: i64.eq $push1=, $pop0, $1{{$}}
+; CHECK-NEXT: return $pop1{{$}}
+define i1 @cmpxchg_i64_success(i64* %p, i64 %exp, i64 %new) {
+  %pair = cmpxchg i64* %p, i64 %exp, i64 %new seq_cst seq_cst
+  %succ = extractvalue { i64, i1 } %pair, 1
+  ret i1 %succ
+}
+
 ;===----------------------------------------------------------------------------
 ; Atomic truncating & sign-extending RMWs
 ;===----------------------------------------------------------------------------
 
 ; add
 
 ; CHECK-LABEL: add_sext_i8_i32:
 ; CHECK-NEXT: .param i32, i32{{$}}

 ; CHECK-NEXT: return $pop2{{$}}
 define i64 @xchg_sext_i32_i64(i32* %p, i64 %v) {
   %t = trunc i64 %v to i32
   %old = atomicrmw xchg i32* %p, i32 %t seq_cst
   %e = sext i32 %old to i64
   ret i64 %e
 }
 
+; cmpxchg
+
+; CHECK-LABEL: cmpxchg_sext_i8_i32:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: i32.extend8_s $push1=, $pop0{{$}}
+; CHECK-NEXT: return $pop1{{$}}
+define i32 @cmpxchg_sext_i8_i32(i8* %p, i32 %exp, i32 %new) {
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %p, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %e = sext i8 %old to i32
+  ret i32 %e
+}
+
+; CHECK-LABEL: cmpxchg_sext_i16_i32:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw16_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: i32.extend16_s $push1=, $pop0{{$}}
+; CHECK-NEXT: return $pop1{{$}}
+define i32 @cmpxchg_sext_i16_i32(i16* %p, i32 %exp, i32 %new) {
+  %exp_t = trunc i32 %exp to i16
+  %new_t = trunc i32 %new to i16
+  %pair = cmpxchg i16* %p, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %e = sext i16 %old to i32
+  ret i32 %e
+}
+
+; CHECK-LABEL: cmpxchg_sext_i8_i64:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw8_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: i64.extend8_s $push1=, $pop0{{$}}
+; CHECK-NEXT: return $pop1{{$}}
+define i64 @cmpxchg_sext_i8_i64(i8* %p, i64 %exp, i64 %new) {
+  %exp_t = trunc i64 %exp to i8
+  %new_t = trunc i64 %new to i8
+  %pair = cmpxchg i8* %p, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %e = sext i8 %old to i64
+  ret i64 %e
+}
+
+; CHECK-LABEL: cmpxchg_sext_i16_i64:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw16_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: i64.extend16_s $push1=, $pop0{{$}}
+; CHECK-NEXT: return $pop1{{$}}
+define i64 @cmpxchg_sext_i16_i64(i16* %p, i64 %exp, i64 %new) {
+  %exp_t = trunc i64 %exp to i16
+  %new_t = trunc i64 %new to i16
+  %pair = cmpxchg i16* %p, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %e = sext i16 %old to i64
+  ret i64 %e
+}
+
+; 32->64 sext rmw gets selected as i32.atomic.rmw.cmpxchg, i64_extend_s/i32
+; CHECK-LABEL: cmpxchg_sext_i32_i64:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i32.wrap/i64 $push1=, $1{{$}}
+; CHECK-NEXT: i32.wrap/i64 $push0=, $2{{$}}
+; CHECK-NEXT: i32.atomic.rmw.cmpxchg $push2=, 0($0), $pop1, $pop0{{$}}
+; CHECK-NEXT: i64.extend_s/i32 $push3=, $pop2{{$}}
+; CHECK-NEXT: return $pop3{{$}}
+define i64 @cmpxchg_sext_i32_i64(i32* %p, i64 %exp, i64 %new) {
+  %exp_t = trunc i64 %exp to i32
+  %new_t = trunc i64 %new to i32
+  %pair = cmpxchg i32* %p, i32 %exp_t, i32 %new_t seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  %e = sext i32 %old to i64
+  ret i64 %e
+}
+
 ;===----------------------------------------------------------------------------
 ; Atomic truncating & zero-extending RMWs
 ;===----------------------------------------------------------------------------
 
 ; add
 
 ; CHECK-LABEL: add_zext_i8_i32:
 ; CHECK-NEXT: .param i32, i32{{$}}

 ; CHECK: i64.atomic.rmw32_u.xchg $push0=, 0($0), $1{{$}}
 ; CHECK-NEXT: return $pop0{{$}}
 define i64 @xchg_zext_i32_i64(i32* %p, i64 %v) {
   %t = trunc i64 %v to i32
   %old = atomicrmw xchg i32* %p, i32 %t seq_cst
   %e = zext i32 %old to i64
   ret i64 %e
 }
+
+; cmpxchg
+
+; CHECK-LABEL: cmpxchg_zext_i8_i32:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_zext_i8_i32(i8* %p, i32 %exp, i32 %new) {
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %p, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %e = zext i8 %old to i32
+  ret i32 %e
+}
+
+; CHECK-LABEL: cmpxchg_zext_i16_i32:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw16_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_zext_i16_i32(i16* %p, i32 %exp, i32 %new) {
+  %exp_t = trunc i32 %exp to i16
+  %new_t = trunc i32 %new to i16
+  %pair = cmpxchg i16* %p, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %e = zext i16 %old to i32
+  ret i32 %e
+}
+
+; CHECK-LABEL: cmpxchg_zext_i8_i64:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw8_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i64 @cmpxchg_zext_i8_i64(i8* %p, i64 %exp, i64 %new) {
+  %exp_t = trunc i64 %exp to i8
+  %new_t = trunc i64 %new to i8
+  %pair = cmpxchg i8* %p, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %e = zext i8 %old to i64
+  ret i64 %e
+}
+
+; CHECK-LABEL: cmpxchg_zext_i16_i64:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw16_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i64 @cmpxchg_zext_i16_i64(i16* %p, i64 %exp, i64 %new) {
+  %exp_t = trunc i64 %exp to i16
+  %new_t = trunc i64 %new to i16
+  %pair = cmpxchg i16* %p, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %e = zext i16 %old to i64
+  ret i64 %e
+}
+
+; CHECK-LABEL: cmpxchg_zext_i32_i64:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw32_u.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i64 @cmpxchg_zext_i32_i64(i32* %p, i64 %exp, i64 %new) {
+  %exp_t = trunc i64 %exp to i32
+  %new_t = trunc i64 %new to i32
+  %pair = cmpxchg i32* %p, i32 %exp_t, i32 %new_t seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  %e = zext i32 %old to i64
+  ret i64 %e
+}

test/CodeGen/WebAssembly/offset-atomics.ll

 ; CHECK-LABEL: rmw_add_i8_i32_retvalue:
 ; CHECK: i32.atomic.rmw8_u.add $push0=, 0($0), $1{{$}}
 ; CHECK-NEXT: return $pop0{{$}}
 define i8 @rmw_add_i8_i32_retvalue(i8 *%p, i32 %v) {
   %t = trunc i32 %v to i8
   %old = atomicrmw add i8* %p, i8 %t seq_cst
   ret i8 %old
 }
+
+;===----------------------------------------------------------------------------
+; Atomic ternary read-modify-writes: 32-bit
+;===----------------------------------------------------------------------------
+
+; Basic RMW.
+
+; CHECK-LABEL: cmpxchg_i32_no_offset:
+; CHECK-NEXT: .param i32, i32, i32{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i32 @cmpxchg_i32_no_offset(i32* %p, i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* %p, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; With an nuw add, we can fold an offset.
+
+; CHECK-LABEL: cmpxchg_i32_with_folded_offset:
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 24($0), $1, $2{{$}}
+define i32 @cmpxchg_i32_with_folded_offset(i32* %p, i32 %exp, i32 %new) {
+  %q = ptrtoint i32* %p to i32
+  %r = add nuw i32 %q, 24
+  %s = inttoptr i32 %r to i32*
+  %pair = cmpxchg i32* %s, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; With an inbounds gep, we can fold an offset.
+
+; CHECK-LABEL: cmpxchg_i32_with_folded_gep_offset:
+; CHECK: i32.atomic.rmw.cmpxchg $push0=, 24($0), $1, $2{{$}}
+define i32 @cmpxchg_i32_with_folded_gep_offset(i32* %p, i32 %exp, i32 %new) {
+  %s = getelementptr inbounds i32, i32* %p, i32 6
+  %pair = cmpxchg i32* %s, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; We can't fold a negative offset though, even with an inbounds gep.
+
+; CHECK-LABEL: cmpxchg_i32_with_unfolded_gep_negative_offset:
+; CHECK: i32.const $push0=, -24{{$}}
+; CHECK: i32.add $push1=, $0, $pop0{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push2=, 0($pop1), $1, $2{{$}}
+define i32 @cmpxchg_i32_with_unfolded_gep_negative_offset(i32* %p, i32 %exp, i32 %new) {
+  %s = getelementptr inbounds i32, i32* %p, i32 -6
+  %pair = cmpxchg i32* %s, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; Without nuw, and even with nsw, we can't fold an offset.
+
+; CHECK-LABEL: cmpxchg_i32_with_unfolded_offset:
+; CHECK: i32.const $push0=, 24{{$}}
+; CHECK: i32.add $push1=, $0, $pop0{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push2=, 0($pop1), $1, $2{{$}}
+define i32 @cmpxchg_i32_with_unfolded_offset(i32* %p, i32 %exp, i32 %new) {
+  %q = ptrtoint i32* %p to i32
+  %r = add nsw i32 %q, 24
+  %s = inttoptr i32 %r to i32*
+  %pair = cmpxchg i32* %s, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; Without inbounds, we can't fold a gep offset.
+
+; CHECK-LABEL: cmpxchg_i32_with_unfolded_gep_offset:
+; CHECK: i32.const $push0=, 24{{$}}
+; CHECK: i32.add $push1=, $0, $pop0{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push2=, 0($pop1), $1, $2{{$}}
+define i32 @cmpxchg_i32_with_unfolded_gep_offset(i32* %p, i32 %exp, i32 %new) {
+  %s = getelementptr i32, i32* %p, i32 6
+  %pair = cmpxchg i32* %s, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; When loading from a fixed address, materialize a zero.
+
+; CHECK-LABEL: cmpxchg_i32_from_numeric_address
+; CHECK: i32.const $push0=, 0{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push1=, 42($pop0), $0, $1{{$}}
+define i32 @cmpxchg_i32_from_numeric_address(i32 %exp, i32 %new) {
+  %s = inttoptr i32 42 to i32*
+  %pair = cmpxchg i32* %s, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+; CHECK-LABEL: cmpxchg_i32_from_global_address
+; CHECK: i32.const $push0=, 0{{$}}
+; CHECK: i32.atomic.rmw.cmpxchg $push1=, gv($pop0), $0, $1{{$}}
+define i32 @cmpxchg_i32_from_global_address(i32 %exp, i32 %new) {
+  %pair = cmpxchg i32* @gv, i32 %exp, i32 %new seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  ret i32 %old
+}
+
+;===----------------------------------------------------------------------------
+; Atomic ternary read-modify-writes: 64-bit
+;===----------------------------------------------------------------------------
+
+; Basic RMW.
+
+; CHECK-LABEL: cmpxchg_i64_no_offset:
+; CHECK-NEXT: .param i32, i64, i64{{$}}
+; CHECK: i64.atomic.rmw.cmpxchg $push0=, 0($0), $1, $2{{$}}
+; CHECK-NEXT: return $pop0{{$}}
+define i64 @cmpxchg_i64_no_offset(i64* %p, i64 %exp, i64 %new) {
+  %pair = cmpxchg i64* %p, i64 %exp, i64 %new seq_cst seq_cst
+  %old = extractvalue { i64, i1 } %pair, 0
+  ret i64 %old
+}
+
+; With an nuw add, we can fold an offset.
+
+; CHECK-LABEL: cmpxchg_i64_with_folded_offset:
+; CHECK: i64.atomic.rmw.cmpxchg $push0=, 24($0), $1, $2{{$}}
+define i64 @cmpxchg_i64_with_folded_offset(i64* %p, i64 %exp, i64 %new) {
+  %q = ptrtoint i64* %p to i32
+  %r = add nuw i32 %q, 24
+  %s = inttoptr i32 %r to i64*
+  %pair = cmpxchg i64* %s, i64 %exp, i64 %new seq_cst seq_cst
+  %old = extractvalue { i64, i1 } %pair, 0
+  ret i64 %old
+}
+
+; With an inbounds gep, we can fold an offset.
+
+; CHECK-LABEL: cmpxchg_i64_with_folded_gep_offset:
+; CHECK: i64.atomic.rmw.cmpxchg $push0=, 24($0), $1, $2{{$}}
+define i64 @cmpxchg_i64_with_folded_gep_offset(i64* %p, i64 %exp, i64 %new) {
+  %s = getelementptr inbounds i64, i64* %p, i32 3
+  %pair = cmpxchg i64* %s, i64 %exp, i64 %new seq_cst seq_cst
+  %old = extractvalue { i64, i1 } %pair, 0
+  ret i64 %old
+}
+
+; We can't fold a negative offset though, even with an inbounds gep.
+
+; CHECK-LABEL: cmpxchg_i64_with_unfolded_gep_negative_offset:
+; CHECK: i32.const $push0=, -24{{$}}
+; CHECK: i32.add $push1=, $0, $pop0{{$}}
+; CHECK: i64.atomic.rmw.cmpxchg $push2=, 0($pop1), $1, $2{{$}}
+define i64 @cmpxchg_i64_with_unfolded_gep_negative_offset(i64* %p, i64 %exp, i64 %new) {
+  %s = getelementptr inbounds i64, i64* %p, i32 -3
+  %pair = cmpxchg i64* %s, i64 %exp, i64 %new seq_cst seq_cst
+  %old = extractvalue { i64, i1 } %pair, 0
+  ret i64 %old
+}
+
+; Without nuw, and even with nsw, we can't fold an offset.
+
+; CHECK-LABEL: cmpxchg_i64_with_unfolded_offset:
+; CHECK: i32.const $push0=, 24{{$}}
+; CHECK: i32.add $push1=, $0, $pop0{{$}}
+; CHECK: i64.atomic.rmw.cmpxchg $push2=, 0($pop1), $1, $2{{$}}
+define i64 @cmpxchg_i64_with_unfolded_offset(i64* %p, i64 %exp, i64 %new) {
+  %q = ptrtoint i64* %p to i32
+  %r = add nsw i32 %q, 24
+  %s = inttoptr i32 %r to i64*
+  %pair = cmpxchg i64* %s, i64 %exp, i64 %new seq_cst seq_cst
+  %old = extractvalue { i64, i1 } %pair, 0
+  ret i64 %old
+}
+
+; Without inbounds, we can't fold a gep offset.
+
+; CHECK-LABEL: cmpxchg_i64_with_unfolded_gep_offset:
+; CHECK: i32.const $push0=, 24{{$}}
+; CHECK: i32.add $push1=, $0, $pop0{{$}}
+; CHECK: i64.atomic.rmw.cmpxchg $push2=, 0($pop1), $1, $2{{$}}
+define i64 @cmpxchg_i64_with_unfolded_gep_offset(i64* %p, i64 %exp, i64 %new) {
+  %s = getelementptr i64, i64* %p, i32 3
+  %pair = cmpxchg i64* %s, i64 %exp, i64 %new seq_cst seq_cst
+  %old = extractvalue { i64, i1 } %pair, 0
+  ret i64 %old
+}
+
+;===----------------------------------------------------------------------------
+; Atomic truncating & sign-extending ternary RMWs
+;===----------------------------------------------------------------------------
+
+; Fold an offset into a sign-extending rmw.
+
+; CHECK-LABEL: cmpxchg_i8_i32_s_with_folded_offset:
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push0=, 24($0), $1, $2{{$}}
+; CHECK-NEXT: i32.extend8_s $push1=, $pop0
+define i32 @cmpxchg_i8_i32_s_with_folded_offset(i8* %p, i32 %exp, i32 %new) {
+  %q = ptrtoint i8* %p to i32
+  %r = add nuw i32 %q, 24
+  %s = inttoptr i32 %r to i8*
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %s, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %u = sext i8 %old to i32
+  ret i32 %u
+}
+
+; 32->64 sext rmw gets selected as i32.atomic.rmw.cmpxchg, i64_extend_s/i32
+; CHECK-LABEL: cmpxchg_i32_i64_s_with_folded_offset:
+; CHECK: i32.wrap/i64 $push1=, $1
+; CHECK-NEXT: i32.wrap/i64 $push0=, $2
+; CHECK-NEXT: i32.atomic.rmw.cmpxchg $push2=, 24($0), $pop1, $pop0{{$}}
+; CHECK-NEXT: i64.extend_s/i32 $push3=, $pop2{{$}}
+define i64 @cmpxchg_i32_i64_s_with_folded_offset(i32* %p, i64 %exp, i64 %new) {
+  %q = ptrtoint i32* %p to i32
+  %r = add nuw i32 %q, 24
+  %s = inttoptr i32 %r to i32*
+  %exp_t = trunc i64 %exp to i32
+  %new_t = trunc i64 %new to i32
+  %pair = cmpxchg i32* %s, i32 %exp_t, i32 %new_t seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  %u = sext i32 %old to i64
+  ret i64 %u
+}
+
+; Fold a gep offset into a sign-extending rmw.
+
+; CHECK-LABEL: cmpxchg_i8_i32_s_with_folded_gep_offset:
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push0=, 24($0), $1, $2{{$}}
+; CHECK-NEXT: i32.extend8_s $push1=, $pop0
+define i32 @cmpxchg_i8_i32_s_with_folded_gep_offset(i8* %p, i32 %exp, i32 %new) {
+  %s = getelementptr inbounds i8, i8* %p, i32 24
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %s, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %u = sext i8 %old to i32
+  ret i32 %u
+}
+
+; CHECK-LABEL: cmpxchg_i16_i32_s_with_folded_gep_offset:
+; CHECK: i32.atomic.rmw16_u.cmpxchg $push0=, 48($0), $1, $2{{$}}
+; CHECK-NEXT: i32.extend16_s $push1=, $pop0
+define i32 @cmpxchg_i16_i32_s_with_folded_gep_offset(i16* %p, i32 %exp, i32 %new) {
+  %s = getelementptr inbounds i16, i16* %p, i32 24
+  %exp_t = trunc i32 %exp to i16
+  %new_t = trunc i32 %new to i16
+  %pair = cmpxchg i16* %s, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %u = sext i16 %old to i32
+  ret i32 %u
+}
+
+; CHECK-LABEL: cmpxchg_i16_i64_s_with_folded_gep_offset:
+; CHECK: i64.atomic.rmw16_u.cmpxchg $push0=, 48($0), $1, $2{{$}}
+; CHECK-NEXT: i64.extend16_s $push1=, $pop0
+define i64 @cmpxchg_i16_i64_s_with_folded_gep_offset(i16* %p, i64 %exp, i64 %new) {
+  %s = getelementptr inbounds i16, i16* %p, i32 24
+  %exp_t = trunc i64 %exp to i16
+  %new_t = trunc i64 %new to i16
+  %pair = cmpxchg i16* %s, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %u = sext i16 %old to i64
+  ret i64 %u
+}
+
+; 'add' in this code becomes 'or' after DAG optimization. Treat an 'or' node as
+; an 'add' if the or'ed bits are known to be zero.
+
+; CHECK-LABEL: cmpxchg_i8_i32_s_with_folded_or_offset:
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push[[R1:[0-9]+]]=, 2($pop{{[0-9]+}}), $1, $2{{$}}
+; CHECK-NEXT: i32.extend8_s $push{{[0-9]+}}=, $pop[[R1]]{{$}}
+define i32 @cmpxchg_i8_i32_s_with_folded_or_offset(i32 %x, i32 %exp, i32 %new) {
+  %and = and i32 %x, -4
+  %t0 = inttoptr i32 %and to i8*
+  %arrayidx = getelementptr inbounds i8, i8* %t0, i32 2
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %arrayidx, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %conv = sext i8 %old to i32
+  ret i32 %conv
+}
+
+; CHECK-LABEL: cmpxchg_i8_i64_s_with_folded_or_offset:
+; CHECK: i64.atomic.rmw8_u.cmpxchg $push[[R1:[0-9]+]]=, 2($pop{{[0-9]+}}), $1, $2{{$}}
+; CHECK-NEXT: i64.extend8_s $push{{[0-9]+}}=, $pop[[R1]]{{$}}
+define i64 @cmpxchg_i8_i64_s_with_folded_or_offset(i32 %x, i64 %exp, i64 %new) {
+  %and = and i32 %x, -4
+  %t0 = inttoptr i32 %and to i8*
+  %arrayidx = getelementptr inbounds i8, i8* %t0, i32 2
+  %exp_t = trunc i64 %exp to i8
+  %new_t = trunc i64 %new to i8
+  %pair = cmpxchg i8* %arrayidx, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %conv = sext i8 %old to i64
+  ret i64 %conv
+}
+
+; When loading from a fixed address, materialize a zero.
+
+; CHECK-LABEL: cmpxchg_i16_i32_s_from_numeric_address
+; CHECK: i32.const $push0=, 0{{$}}
+; CHECK: i32.atomic.rmw16_u.cmpxchg $push1=, 42($pop0), $0, $1{{$}}
+; CHECK-NEXT: i32.extend16_s $push2=, $pop1
+define i32 @cmpxchg_i16_i32_s_from_numeric_address(i32 %exp, i32 %new) {
+  %s = inttoptr i32 42 to i16*
+  %exp_t = trunc i32 %exp to i16
+  %new_t = trunc i32 %new to i16
+  %pair = cmpxchg i16* %s, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %u = sext i16 %old to i32
+  ret i32 %u
+}
+
+; CHECK-LABEL: cmpxchg_i8_i32_s_from_global_address
+; CHECK: i32.const $push0=, 0{{$}}
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push1=, gv8($pop0), $0, $1{{$}}
+; CHECK-NEXT: i32.extend8_s $push2=, $pop1{{$}}
+define i32 @cmpxchg_i8_i32_s_from_global_address(i32 %exp, i32 %new) {
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* @gv8, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %u = sext i8 %old to i32
+  ret i32 %u
+}
+
+;===----------------------------------------------------------------------------
+; Atomic truncating & zero-extending ternary RMWs
+;===----------------------------------------------------------------------------
+
+; Fold an offset into a sign-extending rmw.
+
+; CHECK-LABEL: cmpxchg_i8_i32_z_with_folded_offset:
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push0=, 24($0), $1, $2{{$}}
+define i32 @cmpxchg_i8_i32_z_with_folded_offset(i8* %p, i32 %exp, i32 %new) {
+  %q = ptrtoint i8* %p to i32
+  %r = add nuw i32 %q, 24
+  %s = inttoptr i32 %r to i8*
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %s, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %u = zext i8 %old to i32
+  ret i32 %u
+}
+
+; CHECK-LABEL: cmpxchg_i32_i64_z_with_folded_offset:
+; CHECK: i64.atomic.rmw32_u.cmpxchg $push0=, 24($0), $1, $2{{$}}
+define i64 @cmpxchg_i32_i64_z_with_folded_offset(i32* %p, i64 %exp, i64 %new) {
+  %q = ptrtoint i32* %p to i32
+  %r = add nuw i32 %q, 24
+  %s = inttoptr i32 %r to i32*
+  %exp_t = trunc i64 %exp to i32
+  %new_t = trunc i64 %new to i32
+  %pair = cmpxchg i32* %s, i32 %exp_t, i32 %new_t seq_cst seq_cst
+  %old = extractvalue { i32, i1 } %pair, 0
+  %u = zext i32 %old to i64
+  ret i64 %u
+}
+
+; Fold a gep offset into a sign-extending rmw.
+
+; CHECK-LABEL: cmpxchg_i8_i32_z_with_folded_gep_offset:
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push0=, 24($0), $1, $2{{$}}
+define i32 @cmpxchg_i8_i32_z_with_folded_gep_offset(i8* %p, i32 %exp, i32 %new) {
+  %s = getelementptr inbounds i8, i8* %p, i32 24
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %s, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %u = zext i8 %old to i32
+  ret i32 %u
+}
+
+; CHECK-LABEL: cmpxchg_i16_i32_z_with_folded_gep_offset:
+; CHECK: i32.atomic.rmw16_u.cmpxchg $push0=, 48($0), $1, $2{{$}}
+define i32 @cmpxchg_i16_i32_z_with_folded_gep_offset(i16* %p, i32 %exp, i32 %new) {
+  %s = getelementptr inbounds i16, i16* %p, i32 24
+  %exp_t = trunc i32 %exp to i16
+  %new_t = trunc i32 %new to i16
+  %pair = cmpxchg i16* %s, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %u = zext i16 %old to i32
+  ret i32 %u
+}
+
+; CHECK-LABEL: cmpxchg_i16_i64_z_with_folded_gep_offset:
+; CHECK: i64.atomic.rmw16_u.cmpxchg $push0=, 48($0), $1, $2{{$}}
+define i64 @cmpxchg_i16_i64_z_with_folded_gep_offset(i16* %p, i64 %exp, i64 %new) {
+  %s = getelementptr inbounds i16, i16* %p, i32 24
+  %exp_t = trunc i64 %exp to i16
+  %new_t = trunc i64 %new to i16
+  %pair = cmpxchg i16* %s, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %u = zext i16 %old to i64
+  ret i64 %u
+}
+
+; 'add' in this code becomes 'or' after DAG optimization. Treat an 'or' node as
+; an 'add' if the or'ed bits are known to be zero.
+
+; CHECK-LABEL: cmpxchg_i8_i32_z_with_folded_or_offset:
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push[[R1:[0-9]+]]=, 2($pop{{[0-9]+}}), $1, $2{{$}}
+define i32 @cmpxchg_i8_i32_z_with_folded_or_offset(i32 %x, i32 %exp, i32 %new) {
+  %and = and i32 %x, -4
+  %t0 = inttoptr i32 %and to i8*
+  %arrayidx = getelementptr inbounds i8, i8* %t0, i32 2
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* %arrayidx, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %conv = zext i8 %old to i32
+  ret i32 %conv
+}
+
+; CHECK-LABEL: cmpxchg_i8_i64_z_with_folded_or_offset:
+; CHECK: i64.atomic.rmw8_u.cmpxchg $push[[R1:[0-9]+]]=, 2($pop{{[0-9]+}}), $1, $2{{$}}
+define i64 @cmpxchg_i8_i64_z_with_folded_or_offset(i32 %x, i64 %exp, i64 %new) {
+  %and = and i32 %x, -4
+  %t0 = inttoptr i32 %and to i8*
+  %arrayidx = getelementptr inbounds i8, i8* %t0, i32 2
+  %exp_t = trunc i64 %exp to i8
+  %new_t = trunc i64 %new to i8
+  %pair = cmpxchg i8* %arrayidx, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %conv = zext i8 %old to i64
+  ret i64 %conv
+}
+
+; When loading from a fixed address, materialize a zero.
+
+; CHECK-LABEL: cmpxchg_i16_i32_z_from_numeric_address
+; CHECK: i32.const $push0=, 0{{$}}
+; CHECK: i32.atomic.rmw16_u.cmpxchg $push1=, 42($pop0), $0, $1{{$}}
+define i32 @cmpxchg_i16_i32_z_from_numeric_address(i32 %exp, i32 %new) {
+  %s = inttoptr i32 42 to i16*
+  %exp_t = trunc i32 %exp to i16
+  %new_t = trunc i32 %new to i16
+  %pair = cmpxchg i16* %s, i16 %exp_t, i16 %new_t seq_cst seq_cst
+  %old = extractvalue { i16, i1 } %pair, 0
+  %u = zext i16 %old to i32
+  ret i32 %u
+}
+
+; CHECK-LABEL: cmpxchg_i8_i32_z_from_global_address
+; CHECK: i32.const $push0=, 0{{$}}
+; CHECK: i32.atomic.rmw8_u.cmpxchg $push1=, gv8($pop0), $0, $1{{$}}
+define i32 @cmpxchg_i8_i32_z_from_global_address(i32 %exp, i32 %new) {
+  %exp_t = trunc i32 %exp to i8
+  %new_t = trunc i32 %new to i8
+  %pair = cmpxchg i8* @gv8, i8 %exp_t, i8 %new_t seq_cst seq_cst
+  %old = extractvalue { i8, i1 } %pair, 0
+  %u = zext i8 %old to i32
+  ret i32 %u
+}