[NVPTX] Enable atomic expansion of atomicrmw for NVPTX

[tianshilei1992]

Summary

This patch enables atomic expansion of atomicrmw instruction for NVPTX.

Depend on D125639.

[tianshilei1992]

The test is on the way.

[tra]

Tests?

[tianshilei1992]

add test

[tianshilei1992]

Move to D125639

llvm/lib/Target/NVPTX/NVPTXISelLowering.h

public:
   bool enableAggressiveFMAFusion(EVT VT) const override { return true; }
 
   // The default is to transform llvm.ctlz(x, false) (where false indicates that
   // x == 0 is not undefined behavior) into a branch that checks whether x is 0
   // and avoids calling ctlz in that case.  We have a dedicated ctlz
   // instruction, so we say that ctlz is cheap to speculate.
   bool isCheapToSpeculateCtlz() const override { return true; }
 
+  AtomicExpansionKind
+  shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const override;
+
 private:
   const NVPTXSubtarget &STI; // cache the subtarget here
   SDValue getParamSymbol(SelectionDAG &DAG, int idx, EVT) const;
 
   SDValue LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerCONCAT_VECTORS(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerEXTRACT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
 

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

case ISD::LOAD:
     ReplaceLoadVector(N, DAG, Results);
     return;
   case ISD::INTRINSIC_W_CHAIN:
     ReplaceINTRINSIC_W_CHAIN(N, DAG, Results);
     return;
   }
 }
 
+NVPTXTargetLowering::AtomicExpansionKind
+NVPTXTargetLowering::shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const {
+  Type *Ty = AI->getValOperand()->getType();
+  if (AI->isFloatingPointOperation()) {
+    if (AI->getOperation() == AtomicRMWInst::BinOp::FAdd) {
+      if (Ty->isFloatTy())
+        return AtomicExpansionKind::None;
+      if (Ty->isDoubleTy() && STI.hasAtomAddF64())
+        return AtomicExpansionKind::None;
+    }
+    return AtomicExpansionKind::CmpXChg;
+  }
+
+  switch (AI->getOperation()) {
+  default:
+    return AtomicExpansionKind::CmpXChg;
+  case AtomicRMWInst::BinOp::Add:
+  case AtomicRMWInst::BinOp::Sub:
+  case AtomicRMWInst::BinOp::Max:
+  case AtomicRMWInst::BinOp::Min:
+  case AtomicRMWInst::BinOp::UMax:
+  case AtomicRMWInst::BinOp::UMin:
+  case AtomicRMWInst::BinOp::Xchg:
+  case AtomicRMWInst::BinOp::And:
+  case AtomicRMWInst::BinOp::Or:
+  case AtomicRMWInst::BinOp::Xor:
+    assert(Ty->isIntegerTy());
+    switch (cast<llvm::IntegerType>(Ty)->getBitWidth()) {
+    case 32:
+      return AtomicExpansionKind::None;
+    case 64:
+      return AtomicExpansionKind::None;
+    default:
+      return AtomicExpansionKind::CmpXChg;
+    }
+  }
+
+  return AtomicExpansionKind::CmpXChg;
+}
+
 // Pin NVPTXTargetObjectFile's vtables to this file.
 NVPTXTargetObjectFile::~NVPTXTargetObjectFile() = default;
 
 MCSection *NVPTXTargetObjectFile::SelectSectionForGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
   return getDataSection();
 }

llvm/test/CodeGen/NVPTX/atomic-expand.ll

+; RUN: llc < %s -march=nvptx64 -mcpu=sm_20 | FileCheck %s --check-prefix=CHECK-SM20
+; RUN: llc < %s -march=nvptx64 -mcpu=sm_60 | FileCheck %s --check-prefix=CHECK-SM60
+; RUN: %if ptxas %{ llc < %s -march=nvptx64 -mcpu=sm_20 | %ptxas-verify %}
+; RUN: %if ptxas %{ llc < %s -march=nvptx64 -mcpu=sm_60 | %ptxas-verify %}
+
+; CHECK-LABEL: foo
+define void @foo(ptr %0, double %1) {
+entry:
+  ; CHECK-SM20: atom.cas.b64
+  ; CHECK-SM60: atom.add.f64
+  %2 = atomicrmw fadd ptr %0, double %1 monotonic, align 8
+  ret void
+}