AArch64: Use consistent atomicrmw expansion for FP operations

Use LLSC or cmpxchg in the same cases as for the unsupported
integer operations. This required some fixups to the LLSC
implementatation to deal with the fp128 case.

Author: arsenm

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -27067,9 +27067,6 @@ AArch64TargetLowering::shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const {
   unsigned Size = AI->getType()->getPrimitiveSizeInBits();
   assert(Size <= 128 && "AtomicExpandPass should've handled larger sizes.");
 
-  if (AI->isFloatingPointOperation())
-    return AtomicExpansionKind::CmpXChg;
-
   bool CanUseLSE128 = Subtarget->hasLSE128() && Size == 128 &&
                       (AI->getOperation() == AtomicRMWInst::Xchg ||
                        AI->getOperation() == AtomicRMWInst::Or ||
@@ -27079,7 +27076,8 @@ AArch64TargetLowering::shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const {
 
   // Nand is not supported in LSE.
   // Leave 128 bits to LLSC or CmpXChg.
-  if (AI->getOperation() != AtomicRMWInst::Nand && Size < 128) {
+  if (AI->getOperation() != AtomicRMWInst::Nand && Size < 128 &&
+      !AI->isFloatingPointOperation()) {
     if (Subtarget->hasLSE())
       return AtomicExpansionKind::None;
     if (Subtarget->outlineAtomics()) {
@@ -27152,10 +27150,14 @@ Value *AArch64TargetLowering::emitLoadLinked(IRBuilderBase &Builder,
 
     Value *Lo = Builder.CreateExtractValue(LoHi, 0, "lo");
     Value *Hi = Builder.CreateExtractValue(LoHi, 1, "hi");
-    Lo = Builder.CreateZExt(Lo, ValueTy, "lo64");
-    Hi = Builder.CreateZExt(Hi, ValueTy, "hi64");
-    return Builder.CreateOr(
-        Lo, Builder.CreateShl(Hi, ConstantInt::get(ValueTy, 64)), "val64");
+
+    auto *Int128Ty = Type::getInt128Ty(Builder.getContext());
+    Lo = Builder.CreateZExt(Lo, Int128Ty, "lo64");
+    Hi = Builder.CreateZExt(Hi, Int128Ty, "hi64");
+
+    Value *Or = Builder.CreateOr(
+        Lo, Builder.CreateShl(Hi, ConstantInt::get(Int128Ty, 64)), "val64");
+    return Builder.CreateBitCast(Or, ValueTy);
   }
 
   Type *Tys[] = { Addr->getType() };
@@ -27166,8 +27168,8 @@ Value *AArch64TargetLowering::emitLoadLinked(IRBuilderBase &Builder,
   const DataLayout &DL = M->getDataLayout();
   IntegerType *IntEltTy = Builder.getIntNTy(DL.getTypeSizeInBits(ValueTy));
   CallInst *CI = Builder.CreateCall(Ldxr, Addr);
-  CI->addParamAttr(
-      0, Attribute::get(Builder.getContext(), Attribute::ElementType, ValueTy));
+  CI->addParamAttr(0, Attribute::get(Builder.getContext(),
+                                     Attribute::ElementType, IntEltTy));
   Value *Trunc = Builder.CreateTrunc(CI, IntEltTy);
 
   return Builder.CreateBitCast(Trunc, ValueTy);
@@ -27193,9 +27195,13 @@ Value *AArch64TargetLowering::emitStoreConditional(IRBuilderBase &Builder,
         IsRelease ? Intrinsic::aarch64_stlxp : Intrinsic::aarch64_stxp;
     Function *Stxr = Intrinsic::getDeclaration(M, Int);
     Type *Int64Ty = Type::getInt64Ty(M->getContext());
+    Type *Int128Ty = Type::getInt128Ty(M->getContext());
+
+    Value *CastVal = Builder.CreateBitCast(Val, Int128Ty);
 
-    Value *Lo = Builder.CreateTrunc(Val, Int64Ty, "lo");
-    Value *Hi = Builder.CreateTrunc(Builder.CreateLShr(Val, 64), Int64Ty, "hi");
+    Value *Lo = Builder.CreateTrunc(CastVal, Int64Ty, "lo");
+    Value *Hi =
+        Builder.CreateTrunc(Builder.CreateLShr(CastVal, 64), Int64Ty, "hi");
     return Builder.CreateCall(Stxr, {Lo, Hi, Addr});
   }