[NVPTX] Make GlobalUniqueCallSite a member of NVPTXISelLowering (#130212)

This change moves GlobalUniqueCallSite into NVPTXISelLowering. In
processes where multiple compilations occur, this makes call site
enumeration local to individual compilation, which ensures that call
site numbers are consistently sequential within each compilation and is
independent of other compilations happening in parallel.

Author: AlexMaclean

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

@@ -73,8 +73,6 @@
 
 using namespace llvm;
 
-static std::atomic<unsigned> GlobalUniqueCallSite;
-
 static cl::opt<bool> sched4reg(
     "nvptx-sched4reg",
     cl::desc("NVPTX Specific: schedule for register pressue"), cl::init(false));
@@ -500,7 +498,7 @@ static SDValue MaybeBitcast(SelectionDAG &DAG, SDLoc DL, EVT VT,
 // NVPTXTargetLowering Constructor.
 NVPTXTargetLowering::NVPTXTargetLowering(const NVPTXTargetMachine &TM,
                                          const NVPTXSubtarget &STI)
-    : TargetLowering(TM), nvTM(&TM), STI(STI) {
+    : TargetLowering(TM), nvTM(&TM), STI(STI), GlobalUniqueCallSite(0) {
   // always lower memset, memcpy, and memmove intrinsics to load/store
   // instructions, rather
   // then generating calls to memset, mempcy or memmove.
@@ -1474,7 +1472,7 @@ SDValue NVPTXTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   unsigned FirstVAArg = CLI.NumFixedArgs; // position of the first variadic
   unsigned VAOffset = 0;                  // current offset in the param array
 
-  unsigned UniqueCallSite = GlobalUniqueCallSite.fetch_add(1);
+  const unsigned UniqueCallSite = GlobalUniqueCallSite++;
   SDValue TempChain = Chain;
   Chain = DAG.getCALLSEQ_START(Chain, UniqueCallSite, 0, dl);
   SDValue InGlue = Chain.getValue(1);

llvm/lib/Target/NVPTX/NVPTXISelLowering.h

@@ -273,6 +273,8 @@ class NVPTXTargetLowering : public TargetLowering {
 
 private:
   const NVPTXSubtarget &STI; // cache the subtarget here
+  mutable unsigned GlobalUniqueCallSite;
+
   SDValue getParamSymbol(SelectionDAG &DAG, int idx, EVT) const;
 
   SDValue LowerADDRSPACECAST(SDValue Op, SelectionDAG &DAG) const;