For ARM backend, fixed "byval" attribute support.

Now even the small structures could be passed within byval (small enough
to be stored in GPRs).
In regression tests next function prototypes are checked:

PR15293:
  %artz = type { i32 }
  define void @foo(%artz* byval %s)
  define void @foo2(%artz* byval %s, i32 %p, %artz* byval %s2)
foo: "s" stored in R0
foo2: "s" stored in R0, "s2" stored in R2.

Next AAPCS rules are checked:
5.5 Parameters Passing, C.4 and C.5,
"ParamSize" is parameter size in 32bit words:
-- NSAA != 0, NCRN < R4 and NCRN+ParamSize > R4.
   Parameter should be sent to the stack; NCRN := R4.
-- NSAA != 0, and NCRN < R4, NCRN+ParamSize < R4.
   Parameter stored in GPRs; NCRN += ParamSize.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181148 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 105 insertions, 34 deletions

diff --git a/lib/CodeGen/CallingConvLower.cpp b/lib/CodeGen/CallingConvLower.cpp
index f1d4ace..75f4b96 100644
--- a/lib/CodeGen/CallingConvLower.cpp
+++ b/lib/CodeGen/CallingConvLower.cpp
@@ -32,7 +32,7 @@ CCState::CCState(CallingConv::ID CC, bool isVarArg, MachineFunction &mf,
   // No stack is used.
   StackOffset = 0;
 
-  clearFirstByValReg();
+  clearByValRegsInfo();
   UsedRegs.resize((TRI.getNumRegs()+31)/32);
 }
 
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 9475f1b..0f7beb1 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1481,10 +1481,17 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
 
       // True if this byval aggregate will be split between registers
       // and memory.
-      if (CCInfo.isFirstByValRegValid()) {
+      unsigned ByValArgsCount = CCInfo.getInRegsParamsCount();
+      unsigned CurByValIdx = CCInfo.getInRegsParamsProceed();
+
+      if (CurByValIdx < ByValArgsCount) {
+
+        unsigned RegBegin, RegEnd;
+        CCInfo.getInRegsParamInfo(CurByValIdx, RegBegin, RegEnd);
+
         EVT PtrVT = DAG.getTargetLoweringInfo().getPointerTy();
         unsigned int i, j;
-        for (i = 0, j = CCInfo.getFirstByValReg(); j < ARM::R4; i++, j++) {
+        for (i = 0, j = RegBegin; j < RegEnd; i++, j++) {
           SDValue Const = DAG.getConstant(4*i, MVT::i32);
           SDValue AddArg = DAG.getNode(ISD::ADD, dl, PtrVT, Arg, Const);
           SDValue Load = DAG.getLoad(PtrVT, dl, Chain, AddArg,
@@ -1493,11 +1500,15 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
           MemOpChains.push_back(Load.getValue(1));
           RegsToPass.push_back(std::make_pair(j, Load));
         }
-        offset = ARM::R4 - CCInfo.getFirstByValReg();
-        CCInfo.clearFirstByValReg();
+
+        // If parameter size outsides register area, "offset" value
+        // helps us to calculate stack slot for remained part properly.
+        offset = RegEnd - RegBegin;
+
+        CCInfo.nextInRegsParam();
       }
 
-      if (Flags.getByValSize() - 4*offset > 0) {
+      if (Flags.getByValSize() > 4*offset) {
         unsigned LocMemOffset = VA.getLocMemOffset();
         SDValue StkPtrOff = DAG.getIntPtrConstant(LocMemOffset);
         SDValue Dst = DAG.getNode(ISD::ADD, dl, getPointerTy(), StackPtr,
@@ -1740,9 +1751,24 @@ ARMTargetLowering::HandleByVal(
   assert((State->getCallOrPrologue() == Prologue ||
           State->getCallOrPrologue() == Call) &&
          "unhandled ParmContext");
-  if ((!State->isFirstByValRegValid()) &&
-      (!Subtarget->isAAPCS_ABI() || State->getNextStackOffset() == 0) &&
-      (ARM::R0 <= reg) && (reg <= ARM::R3)) {
+
+  // For in-prologue parameters handling, we also introduce stack offset
+  // for byval registers: see CallingConvLower.cpp, CCState::HandleByVal.
+  // This behaviour outsides AAPCS rules (5.5 Parameters Passing) of how
+  // NSAA should be evaluted (NSAA means "next stacked argument address").
+  // So: NextStackOffset = NSAAOffset + SizeOfByValParamsStoredInRegs.
+  // Then: NSAAOffset = NextStackOffset - SizeOfByValParamsStoredInRegs.
+  unsigned NSAAOffset = State->getNextStackOffset();
+  if (State->getCallOrPrologue() != Call) {
+    for (unsigned i = 0, e = State->getInRegsParamsCount(); i != e; ++i) {
+      unsigned RB, RE;
+      State->getInRegsParamInfo(i, RB, RE);
+      assert(NSAAOffset >= (RE-RB)*4 &&
+             "Stack offset for byval regs doesn't introduced anymore?");
+      NSAAOffset -= (RE-RB)*4;
+    }
+  }
+  if ((ARM::R0 <= reg) && (reg <= ARM::R3)) {
     if (Subtarget->isAAPCS_ABI() && Align > 4) {
       unsigned AlignInRegs = Align / 4;
       unsigned Waste = (ARM::R4 - reg) % AlignInRegs;
@@ -1750,22 +1776,45 @@ ARMTargetLowering::HandleByVal(
         reg = State->AllocateReg(GPRArgRegs, 4);
     }
     if (reg != 0) {
-      State->setFirstByValReg(reg);
+      unsigned excess = 4 * (ARM::R4 - reg);
+
+      // Special case when NSAA != SP and parameter size greater than size of
+      // all remained GPR regs. In that case we can't split parameter, we must
+      // send it to stack. We also must set NCRN to R4, so waste all
+      // remained registers.
+      if (Subtarget->isAAPCS_ABI() && NSAAOffset != 0 && size > excess) {
+        while (State->AllocateReg(GPRArgRegs, 4))
+          ;
+        return;
+      }
+
+      // First register for byval parameter is the first register that wasn't
+      // allocated before this method call, so it would be "reg".
+      // If parameter is small enough to be saved in range [reg, r4), then
+      // the end (first after last) register would be reg + param-size-in-regs,
+      // else parameter would be splitted between registers and stack,
+      // end register would be r4 in this case.
+      unsigned ByValRegBegin = reg;
+      unsigned ByValRegEnd = (size < excess) ? reg + size/4 : ARM::R4;
+      State->addInRegsParamInfo(ByValRegBegin, ByValRegEnd);
+      // Note, first register is allocated in the beginning of function already,
+      // allocate remained amount of registers we need.
+      for (unsigned i = reg+1; i != ByValRegEnd; ++i)
+        State->AllocateReg(GPRArgRegs, 4);
       // At a call site, a byval parameter that is split between
       // registers and memory needs its size truncated here.  In a
       // function prologue, such byval parameters are reassembled in
       // memory, and are not truncated.
       if (State->getCallOrPrologue() == Call) {
-        unsigned excess = 4 * (ARM::R4 - reg);
-        assert(size >= excess && "expected larger existing stack allocation");
-        size -= excess;
+        // Make remained size equal to 0 in case, when
+        // the whole structure may be stored into registers.
+        if (size < excess)
+          size = 0;
+        else
+          size -= excess;
       }
     }
   }
-  // Confiscate any remaining parameter registers to preclude their
-  // assignment to subsequent parameters.
-  while (State->AllocateReg(GPRArgRegs, 4))
-    ;
 }
 
 /// MatchingStackOffset - Return true if the given stack call argument is
@@ -2580,13 +2629,16 @@ ARMTargetLowering::GetF64FormalArgument(CCValAssign &VA, CCValAssign &NextVA,
 
 void
 ARMTargetLowering::computeRegArea(CCState &CCInfo, MachineFunction &MF,
+                                  unsigned InRegsParamRecordIdx,
                                   unsigned &ArgRegsSize,
                                   unsigned &ArgRegsSaveSize)
   const {
   unsigned NumGPRs;
-  if (CCInfo.isFirstByValRegValid())
-    NumGPRs = ARM::R4 - CCInfo.getFirstByValReg();
-  else {
+  if (InRegsParamRecordIdx < CCInfo.getInRegsParamsCount()) {
+    unsigned RBegin, REnd;
+    CCInfo.getInRegsParamInfo(InRegsParamRecordIdx, RBegin, REnd);
+    NumGPRs = REnd - RBegin;
+  } else {
     unsigned int firstUnalloced;
     firstUnalloced = CCInfo.getFirstUnallocated(GPRArgRegs,
                                                 sizeof(GPRArgRegs) /
@@ -2611,6 +2663,7 @@ int
 ARMTargetLowering::StoreByValRegs(CCState &CCInfo, SelectionDAG &DAG,
                                   DebugLoc dl, SDValue &Chain,
                                   const Value *OrigArg,
+                                  unsigned InRegsParamRecordIdx,
                                   unsigned OffsetFromOrigArg,
                                   unsigned ArgOffset,
                                   bool ForceMutable) const {
@@ -2629,24 +2682,26 @@ ARMTargetLowering::StoreByValRegs(CCState &CCInfo, SelectionDAG &DAG,
   MachineFunction &MF = DAG.getMachineFunction();
   MachineFrameInfo *MFI = MF.getFrameInfo();
   ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
-  unsigned firstRegToSaveIndex;
-  if (CCInfo.isFirstByValRegValid())
-    firstRegToSaveIndex = CCInfo.getFirstByValReg() - ARM::R0;
-  else {
+  unsigned firstRegToSaveIndex, lastRegToSaveIndex;
+  unsigned RBegin, REnd;
+  if (InRegsParamRecordIdx < CCInfo.getInRegsParamsCount()) {
+    CCInfo.getInRegsParamInfo(InRegsParamRecordIdx, RBegin, REnd);
+    firstRegToSaveIndex = RBegin - ARM::R0;
+    lastRegToSaveIndex = REnd - ARM::R0;
+  } else {
     firstRegToSaveIndex = CCInfo.getFirstUnallocated
       (GPRArgRegs, sizeof(GPRArgRegs) / sizeof(GPRArgRegs[0]));
+    lastRegToSaveIndex = 4;
   }
 
   unsigned ArgRegsSize, ArgRegsSaveSize;
-  computeRegArea(CCInfo, MF, ArgRegsSize, ArgRegsSaveSize);
+  computeRegArea(CCInfo, MF, InRegsParamRecordIdx, ArgRegsSize, ArgRegsSaveSize);
 
   // Store any by-val regs to their spots on the stack so that they may be
   // loaded by deferencing the result of formal parameter pointer or va_next.
   // Note: once stack area for byval/varargs registers
   // was initialized, it can't be initialized again.
-  if (!AFI->getArgRegsSaveSize() && ArgRegsSaveSize) {
-
-    AFI->setArgRegsSaveSize(ArgRegsSaveSize);
+  if (ArgRegsSaveSize) {
 
     int FrameIndex = MFI->CreateFixedObject(
                       ArgRegsSaveSize,
@@ -2655,7 +2710,8 @@ ARMTargetLowering::StoreByValRegs(CCState &CCInfo, SelectionDAG &DAG,
     SDValue FIN = DAG.getFrameIndex(FrameIndex, getPointerTy());
 
     SmallVector<SDValue, 4> MemOps;
-    for (unsigned i = 0; firstRegToSaveIndex < 4; ++firstRegToSaveIndex, ++i) {
+    for (unsigned i = 0; firstRegToSaveIndex < lastRegToSaveIndex;
+         ++firstRegToSaveIndex, ++i) {
       const TargetRegisterClass *RC;
       if (AFI->isThumb1OnlyFunction())
         RC = &ARM::tGPRRegClass;
@@ -2672,6 +2728,9 @@ ARMTargetLowering::StoreByValRegs(CCState &CCInfo, SelectionDAG &DAG,
       FIN = DAG.getNode(ISD::ADD, dl, getPointerTy(), FIN,
                         DAG.getConstant(4, getPointerTy()));
     }
+
+    AFI->setArgRegsSaveSize(ArgRegsSaveSize + AFI->getArgRegsSaveSize());
+
     if (!MemOps.empty())
       Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
                           &MemOps[0], MemOps.size());
@@ -2696,7 +2755,8 @@ ARMTargetLowering::VarArgStyleRegisters(CCState &CCInfo, SelectionDAG &DAG,
   // If there is no regs to be stored, just point address after last
   // argument passed via stack.
   int FrameIndex =
-    StoreByValRegs(CCInfo, DAG, dl, Chain, 0, 0, ArgOffset, ForceMutable);
+    StoreByValRegs(CCInfo, DAG, dl, Chain, 0, CCInfo.getInRegsParamsCount(),
+                   0, ArgOffset, ForceMutable);
 
   AFI->setVarArgsFrameIndex(FrameIndex);
 }
@@ -2727,6 +2787,12 @@ ARMTargetLowering::LowerFormalArguments(SDValue Chain,
   SDValue ArgValue;
   Function::const_arg_iterator CurOrigArg = MF.getFunction()->arg_begin();
   unsigned CurArgIdx = 0;
+
+  // Initially ArgRegsSaveSize is zero.
+  // Then we increase this value each time we meet byval parameter.
+  // We also increase this value in case of varargs function.
+  AFI->setArgRegsSaveSize(0);
+
   for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
     CCValAssign &VA = ArgLocs[i];
     std::advance(CurOrigArg, Ins[VA.getValNo()].OrigArgIndex - CurArgIdx);
@@ -2824,12 +2890,15 @@ ARMTargetLowering::LowerFormalArguments(SDValue Chain,
           // Since they could be overwritten by lowering of arguments in case of
           // a tail call.
           if (Flags.isByVal()) {
+            unsigned CurByValIndex = CCInfo.getInRegsParamsProceed();
             int FrameIndex = StoreByValRegs(
-                                CCInfo, DAG, dl, Chain, CurOrigArg,
-                                Ins[VA.getValNo()].PartOffset,
-                                VA.getLocMemOffset(),
-                                true /*force mutable frames*/);
+                CCInfo, DAG, dl, Chain, CurOrigArg,
+                CurByValIndex,
+                Ins[VA.getValNo()].PartOffset,
+                VA.getLocMemOffset(),
+                true /*force mutable frames*/);
             InVals.push_back(DAG.getFrameIndex(FrameIndex, getPointerTy()));
+            CCInfo.nextInRegsParam();
           } else {
             int FI = MFI->CreateFixedObject(VA.getLocVT().getSizeInBits()/8,
                                             VA.getLocMemOffset(), true);
diff --git a/lib/Target/ARM/ARMISelLowering.h b/lib/Target/ARM/ARMISelLowering.h
index 46b8438..426010e 100644
--- a/lib/Target/ARM/ARMISelLowering.h
+++ b/lib/Target/ARM/ARMISelLowering.h
@@ -477,6 +477,7 @@ namespace llvm {
     int StoreByValRegs(CCState &CCInfo, SelectionDAG &DAG,
                        DebugLoc dl, SDValue &Chain,
                        const Value *OrigArg,
+                       unsigned InRegsParamRecordIdx,
                        unsigned OffsetFromOrigArg,
                        unsigned ArgOffset,
                        bool ForceMutable) const;
@@ -487,6 +488,7 @@ namespace llvm {
                               bool ForceMutable = false) const;
 
     void computeRegArea(CCState &CCInfo, MachineFunction &MF,
+                        unsigned InRegsParamRecordIdx,
                         unsigned &ArgRegsSize,
                         unsigned &ArgRegsSaveSize) const;