[PowerPC][AIX] Using milicode for memcmp instead of libcall (#147093)

AIX has "millicode" routines, which are functions loaded at boot time
into fixed addresses in kernel memory. This allows them to be customized
for the processor. The __memcmp routine is a millicode implementation;
we use millicode for the memcmp function instead of a library call to
improve performance.

Author: diggerlin

llvm/include/llvm/CodeGen/SelectionDAG.h

@@ -1260,6 +1260,9 @@ class SelectionDAG {
   /// stack arguments from being clobbered.
   LLVM_ABI SDValue getStackArgumentTokenFactor(SDValue Chain);
 
+  std::pair<SDValue, SDValue> getMemcmp(SDValue Chain, const SDLoc &dl,
+                                        SDValue Dst, SDValue Src, SDValue Size,
+                                        const CallInst *CI);
   /* \p CI if not null is the memset call being lowered.
    * \p OverrideTailCall is an optional parameter that can be used to override
    * the tail call optimization decision. */

llvm/include/llvm/CodeGen/SelectionDAGTargetInfo.h

@@ -23,6 +23,7 @@
 
 namespace llvm {
 
+class CallInst;
 class SelectionDAG;
 
 //===----------------------------------------------------------------------===//
@@ -118,8 +119,7 @@ class SelectionDAGTargetInfo {
   virtual std::pair<SDValue, SDValue>
   EmitTargetCodeForMemcmp(SelectionDAG &DAG, const SDLoc &dl, SDValue Chain,
                           SDValue Op1, SDValue Op2, SDValue Op3,
-                          MachinePointerInfo Op1PtrInfo,
-                          MachinePointerInfo Op2PtrInfo) const {
+                          const CallInst *CI) const {
     return std::make_pair(SDValue(), SDValue());
   }
 

llvm/include/llvm/IR/RuntimeLibcalls.td

@@ -276,6 +276,7 @@ foreach FPTy = ["F32", "F64", "F128", "PPCF128"] in {
 }
 
 // Memory
+def MEMCMP : RuntimeLibcall;
 def MEMCPY : RuntimeLibcall;
 def MEMMOVE : RuntimeLibcall;
 def MEMSET : RuntimeLibcall;
@@ -1990,12 +1991,14 @@ defset list<RuntimeLibcallImpl> PPCRuntimeLibcalls = {
 }
 
 defset list<RuntimeLibcallImpl> PPC64AIXCallList = {
+  def ___memcmp64 : RuntimeLibcallImpl<MEMCMP>;
   def ___memmove64 : RuntimeLibcallImpl<MEMCPY>;
   def ___memset64 : RuntimeLibcallImpl<MEMSET>;
   def ___bzero64 : RuntimeLibcallImpl<BZERO>;
 }
 
 defset list<RuntimeLibcallImpl> PPC32AIXCallList = {
+  def ___memcmp : RuntimeLibcallImpl<MEMCMP>;
   def ___memmove : RuntimeLibcallImpl<MEMMOVE>;
   def ___memset : RuntimeLibcallImpl<MEMSET>;
   def ___bzero : RuntimeLibcallImpl<BZERO>;

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -8889,6 +8889,44 @@ static void checkAddrSpaceIsValidForLibcall(const TargetLowering *TLI,
   }
 }
 
+std::pair<SDValue, SDValue>
+SelectionDAG::getMemcmp(SDValue Chain, const SDLoc &dl, SDValue Mem0,
+                        SDValue Mem1, SDValue Size, const CallInst *CI) {
+  const char *LibCallName = TLI->getLibcallName(RTLIB::MEMCMP);
+  if (!LibCallName)
+    return {};
+
+  // Emit a library call.
+  auto GetEntry = [](Type *Ty, SDValue &SDV) {
+    TargetLowering::ArgListEntry E;
+    E.Ty = Ty;
+    E.Node = SDV;
+    return E;
+  };
+
+  PointerType *PT = PointerType::getUnqual(*getContext());
+  TargetLowering::ArgListTy Args = {
+      GetEntry(PT, Mem0), GetEntry(PT, Mem1),
+      GetEntry(getDataLayout().getIntPtrType(*getContext()), Size)};
+
+  TargetLowering::CallLoweringInfo CLI(*this);
+  bool IsTailCall = false;
+  bool ReturnsFirstArg = CI && funcReturnsFirstArgOfCall(*CI);
+  IsTailCall = CI && CI->isTailCall() &&
+               isInTailCallPosition(*CI, getTarget(), ReturnsFirstArg);
+
+  CLI.setDebugLoc(dl)
+      .setChain(Chain)
+      .setLibCallee(
+          TLI->getLibcallCallingConv(RTLIB::MEMCMP),
+          Type::getInt32Ty(*getContext()),
+          getExternalSymbol(LibCallName, TLI->getPointerTy(getDataLayout())),
+          std::move(Args))
+      .setTailCall(IsTailCall);
+
+  return TLI->LowerCallTo(CLI);
+}
+
 SDValue SelectionDAG::getMemcpy(
     SDValue Chain, const SDLoc &dl, SDValue Dst, SDValue Src, SDValue Size,
     Align Alignment, bool isVol, bool AlwaysInline, const CallInst *CI,

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -9090,7 +9090,7 @@ bool SelectionDAGBuilder::visitMemCmpBCmpCall(const CallInst &I) {
   const SelectionDAGTargetInfo &TSI = DAG.getSelectionDAGInfo();
   std::pair<SDValue, SDValue> Res = TSI.EmitTargetCodeForMemcmp(
       DAG, getCurSDLoc(), DAG.getRoot(), getValue(LHS), getValue(RHS),
-      getValue(Size), MachinePointerInfo(LHS), MachinePointerInfo(RHS));
+      getValue(Size), &I);
   if (Res.first.getNode()) {
     processIntegerCallValue(I, Res.first, true);
     PendingLoads.push_back(Res.second);

llvm/lib/Target/PowerPC/PPCSelectionDAGInfo.cpp

@@ -22,3 +22,9 @@ bool PPCSelectionDAGInfo::isTargetStrictFPOpcode(unsigned Opcode) const {
   return Opcode >= PPCISD::FIRST_STRICTFP_OPCODE &&
          Opcode <= PPCISD::LAST_STRICTFP_OPCODE;
 }
+
+std::pair<SDValue, SDValue> PPCSelectionDAGInfo::EmitTargetCodeForMemcmp(
+    SelectionDAG &DAG, const SDLoc &dl, SDValue Chain, SDValue Op1, SDValue Op2,
+    SDValue Op3, const CallInst *CI) const {
+  return DAG.getMemcmp(Chain, dl, Op1, Op2, Op3, CI);
+}

llvm/lib/Target/PowerPC/PPCSelectionDAGInfo.h

@@ -20,6 +20,11 @@ class PPCSelectionDAGInfo : public SelectionDAGTargetInfo {
   bool isTargetMemoryOpcode(unsigned Opcode) const override;
 
   bool isTargetStrictFPOpcode(unsigned Opcode) const override;
+
+  std::pair<SDValue, SDValue>
+  EmitTargetCodeForMemcmp(SelectionDAG &DAG, const SDLoc &dl, SDValue Chain,
+                          SDValue Op1, SDValue Op2, SDValue Op3,
+                          const CallInst *CI) const;
 };
 
 } // namespace llvm

llvm/lib/Target/SystemZ/SystemZSelectionDAGInfo.cpp

@@ -181,8 +181,7 @@ static SDValue addIPMSequence(const SDLoc &DL, SDValue CCReg,
 
 std::pair<SDValue, SDValue> SystemZSelectionDAGInfo::EmitTargetCodeForMemcmp(
     SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Src1,
-    SDValue Src2, SDValue Size, MachinePointerInfo Op1PtrInfo,
-    MachinePointerInfo Op2PtrInfo) const {
+    SDValue Src2, SDValue Size, const CallInst *CI) const {
   SDValue CCReg;
   // Swap operands to invert CC == 1 vs. CC == 2 cases.
   if (auto *CSize = dyn_cast<ConstantSDNode>(Size)) {

llvm/lib/Target/SystemZ/SystemZSelectionDAGInfo.h

@@ -41,8 +41,7 @@ class SystemZSelectionDAGInfo : public SelectionDAGTargetInfo {
   std::pair<SDValue, SDValue>
   EmitTargetCodeForMemcmp(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain,
                           SDValue Src1, SDValue Src2, SDValue Size,
-                          MachinePointerInfo Op1PtrInfo,
-                          MachinePointerInfo Op2PtrInfo) const override;
+                          const CallInst *CI) const override;
 
   std::pair<SDValue, SDValue>
   EmitTargetCodeForMemchr(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain,

llvm/test/CodeGen/PowerPC/memintr32.ll

@@ -11,7 +11,7 @@ define i32 @memcmp_test(ptr nocapture noundef readonly %ptr1, ptr nocapture noun
 ; CHECK-AIX-32-P9-NEXT:    mflr r0
 ; CHECK-AIX-32-P9-NEXT:    stwu r1, -64(r1)
 ; CHECK-AIX-32-P9-NEXT:    stw r0, 72(r1)
-; CHECK-AIX-32-P9-NEXT:    bl .memcmp[PR]
+; CHECK-AIX-32-P9-NEXT:    bl .___memcmp[PR]
 ; CHECK-AIX-32-P9-NEXT:    nop
 ; CHECK-AIX-32-P9-NEXT:    addi r1, r1, 64
 ; CHECK-AIX-32-P9-NEXT:    lwz r0, 8(r1)