[Thumb] Make the load/store optimizer less conservative

[mroth]

Summary

This is a fixed version of rL208992 - all known bugs should be fixed and it passes all the tests I'm running.

For Thumb1, the load/store optimizer will currently only merge LDRs/STRs if the base register is dead after the merged LDM/STM, or if there is no writeback to the base register.

However, this is overly conservative. If the condition flags aren't live at the location where we want to merge, we can do a few other things:

• Reset the base register writeback with a SUBS.
• Try to update future instructions such as ADDS/SUBS with the base register (as long as their definition of the CPSR is also dead).

This patch adds a function that will try to go forward in the basic block and modify any instructions that use the new value of the base register with writeback applied. If it encounters any hazards, it resets the base register to the old value.

I'll try to find a test case for rL217881 as a follow-up commit.

Cheers
Moritz

[rengolin]

Hi Moritz,

Thanks for running this over again. Apart from the nit pick (that was already there, so not a big deal), looks good.

cheers,
--renato

lib/Target/ARM/ARMLoadStoreOptimizer.cpp

178

nit pick, but getAM{3,5}Op() could be merged into a variable like the one above (or maybe conditionalise on isAM3 for both above) and just have OP == sub down below.

[mroth]

Hi Renato,

Thanks for the review. I've refactored the code as you suggested and committed as rL218386.

Cheers
Moritz

lib/Target/ARM/ARMLoadStoreOptimizer.cpp

struct MemOpQueueEntry {
         : Offset(o), Reg(r), isKill(k), Position(p), MBBI(i), Merged(false) {}
     };
     typedef SmallVector<MemOpQueueEntry,8> MemOpQueue;
     typedef MemOpQueue::iterator MemOpQueueIter;
 
     void findUsesOfImpDef(SmallVectorImpl<MachineOperand *> &UsesOfImpDefs,
                           const MemOpQueue &MemOps, unsigned DefReg,
                           unsigned RangeBegin, unsigned RangeEnd);
+    void UpdateBaseRegUses(MachineBasicBlock &MBB,
+                           MachineBasicBlock::iterator MBBI,
+                           DebugLoc dl, unsigned Base, unsigned WordOffset,
+                           ARMCC::CondCodes Pred, unsigned PredReg);
     bool MergeOps(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
                   int Offset, unsigned Base, bool BaseKill, int Opcode,
                   ARMCC::CondCodes Pred, unsigned PredReg, unsigned Scratch,
                   DebugLoc dl,
                   ArrayRef<std::pair<unsigned, bool> > Regs,
                   ArrayRef<unsigned> ImpDefs);
     void MergeOpsUpdate(MachineBasicBlock &MBB,
                         MemOpQueue &MemOps,
bool MergeBaseUpdateLSMultiple(MachineBasicBlock &MBB,
                                    bool &Advance,
                                    MachineBasicBlock::iterator &I);
     bool LoadStoreMultipleOpti(MachineBasicBlock &MBB);
     bool MergeReturnIntoLDM(MachineBasicBlock &MBB);
   };
   char ARMLoadStoreOpt::ID = 0;
 }
 
+static bool definesCPSR(const MachineInstr *MI) {
+  for (const auto &MO : MI->operands()) {
+    if (!MO.isReg())
+      continue;
+    if (MO.isDef() && MO.getReg() == ARM::CPSR && !MO.isDead())
+      // If the instruction has live CPSR def, then it's not safe to fold it
+      // into load / store.
+      return true;
+  }
+
+  return false;
+}
+
+static int getMemoryOpOffset(const MachineInstr *MI) {
+  int Opcode = MI->getOpcode();
+  bool isAM3 = Opcode == ARM::LDRD || Opcode == ARM::STRD;
+  unsigned NumOperands = MI->getDesc().getNumOperands();
+  unsigned OffField = MI->getOperand(NumOperands-3).getImm();
+
+  if (Opcode == ARM::t2LDRi12 || Opcode == ARM::t2LDRi8 ||
+      Opcode == ARM::t2STRi12 || Opcode == ARM::t2STRi8 ||
+      Opcode == ARM::t2LDRDi8 || Opcode == ARM::t2STRDi8 ||
+      Opcode == ARM::LDRi12   || Opcode == ARM::STRi12)
+    return OffField;
+
+  // Thumb1 immediate offsets are scaled by 4
+  if (Opcode == ARM::tLDRi || Opcode == ARM::tSTRi)
+    return OffField * 4;
+
+  int Offset = isAM3 ? ARM_AM::getAM3Offset(OffField)
+    : ARM_AM::getAM5Offset(OffField) * 4;
+  if (isAM3) {
+    if (ARM_AM::getAM3Op(OffField) == ARM_AM::sub)
+      Offset = -Offset;
+  } else {
+    if (ARM_AM::getAM5Op(OffField) == ARM_AM::sub)
+      Offset = -Offset;
+  }
+  return Offset;
+}
+
 static int getLoadStoreMultipleOpcode(int Opcode, ARM_AM::AMSubMode Mode) {
   switch (Opcode) {
   default: llvm_unreachable("Unhandled opcode!");
   case ARM::LDRi12:
     ++NumLDMGened;
     switch (Mode) {
     default: llvm_unreachable("Unhandled submode!");
     case ARM_AM::ia: return ARM::LDMIA;

 static bool isT2i32Store(unsigned Opc) {
   return Opc == ARM::t2STRi12 || Opc == ARM::t2STRi8;
 }
 
 static bool isi32Store(unsigned Opc) {
   return Opc == ARM::STRi12 || isT1i32Store(Opc) || isT2i32Store(Opc);
 }
 
+static unsigned getImmScale(unsigned Opc) {
+  switch (Opc) {
+  default: llvm_unreachable("Unhandled opcode!");
+  case ARM::tLDRi:
+  case ARM::tSTRi:
+    return 1;
+  case ARM::tLDRHi:
+  case ARM::tSTRHi:
+    return 2;
+  case ARM::tLDRBi:
+  case ARM::tSTRBi:
+    return 4;
+  }
+}
+
+/// Update future uses of the base register with the offset introduced
+/// due to writeback. This function only works on Thumb1.
+void
+ARMLoadStoreOpt::UpdateBaseRegUses(MachineBasicBlock &MBB,
+                                   MachineBasicBlock::iterator MBBI,
+                                   DebugLoc dl, unsigned Base,
+                                   unsigned WordOffset,
+                                   ARMCC::CondCodes Pred, unsigned PredReg) {
+  assert(isThumb1 && "Can only update base register uses for Thumb1!");
+  // Start updating any instructions with immediate offsets. Insert a SUB before
+  // the first non-updateable instruction (if any).
+  for (; MBBI != MBB.end(); ++MBBI) {
+    bool InsertSub = false;
+    unsigned Opc = MBBI->getOpcode();
+
+    if (MBBI->readsRegister(Base)) {
+      int Offset;
+      bool IsLoad =
+        Opc == ARM::tLDRi || Opc == ARM::tLDRHi || Opc == ARM::tLDRBi;
+      bool IsStore =
+        Opc == ARM::tSTRi || Opc == ARM::tSTRHi || Opc == ARM::tSTRBi;
+
+      if (IsLoad || IsStore) {
+        // Loads and stores with immediate offsets can be updated, but only if
+        // the new offset isn't negative.
+        // The MachineOperand containing the offset immediate is the last one
+        // before predicates.
+        MachineOperand &MO =
+          MBBI->getOperand(MBBI->getDesc().getNumOperands() - 3);
+        // The offsets are scaled by 1, 2 or 4 depending on the Opcode.
+        Offset = MO.getImm() - WordOffset * getImmScale(Opc);
+
+        // If storing the base register, it needs to be reset first.
+        unsigned InstrSrcReg = MBBI->getOperand(0).getReg();
+
+        if (Offset >= 0 && !(IsStore && InstrSrcReg == Base))
+          MO.setImm(Offset);
+        else
+          InsertSub = true;
+
+      } else if ((Opc == ARM::tSUBi8 || Opc == ARM::tADDi8) &&
+                 !definesCPSR(MBBI)) {
+        // SUBS/ADDS using this register, with a dead def of the CPSR.
+        // Merge it with the update; if the merged offset is too large,
+        // insert a new sub instead.
+        MachineOperand &MO =
+          MBBI->getOperand(MBBI->getDesc().getNumOperands() - 3);
+        Offset = (Opc == ARM::tSUBi8) ?
+          MO.getImm() + WordOffset * 4 :
+          MO.getImm() - WordOffset * 4 ;
+        if (Offset >= 0 && TL->isLegalAddImmediate(Offset)) {
+          // FIXME: Swap ADDS<->SUBS if Offset < 0, erase instruction if
+          // Offset == 0.
+          MO.setImm(Offset);
+          // The base register has now been reset, so exit early.
+          return;
+        } else {
+          InsertSub = true;
+        }
+
+      } else {
+        // Can't update the instruction.
+        InsertSub = true;
+      }
+
+    } else if (definesCPSR(MBBI) || MBBI->isCall() || MBBI->isBranch()) {
+      // Since SUBS sets the condition flags, we can't place the base reset
+      // after an instruction that has a live CPSR def.
+      // The base register might also contain an argument for a function call.
+      InsertSub = true;
+    }
+
+    if (InsertSub) {
+      // An instruction above couldn't be updated, so insert a sub.
+      AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII->get(ARM::tSUBi8), Base), true)
+        .addReg(Base, getKillRegState(false)).addImm(WordOffset * 4)
+        .addImm(Pred).addReg(PredReg);
+      return;
+    }
+
+    if (MBBI->killsRegister(Base))
+      // Register got killed. Stop updating.
+      return;
+  }
+
+  // End of block was reached.
+  if (MBB.succ_size() > 0) {
+    // FIXME: Because of a bug, live registers are sometimes missing from
+    // the successor blocks' live-in sets. This means we can't trust that
+    // information and *always* have to reset at the end of a block.
+    // See PR21029.
+    if (MBBI != MBB.end()) --MBBI;
+    AddDefaultT1CC(
+      BuildMI(MBB, MBBI, dl, TII->get(ARM::tSUBi8), Base), true)
+      .addReg(Base, getKillRegState(false)).addImm(WordOffset * 4)
+      .addImm(Pred).addReg(PredReg);
+  }
+}
+
 /// MergeOps - Create and insert a LDM or STM with Base as base register and
 /// registers in Regs as the register operands that would be loaded / stored.
 /// It returns true if the transformation is done.
 bool
 ARMLoadStoreOpt::MergeOps(MachineBasicBlock &MBB,
                           MachineBasicBlock::iterator MBBI,
                           int Offset, unsigned Base, bool BaseKill,
                           int Opcode, ARMCC::CondCodes Pred,
                           unsigned PredReg, unsigned Scratch, DebugLoc dl,
                           ArrayRef<std::pair<unsigned, bool> > Regs,
                           ArrayRef<unsigned> ImpDefs) {
   // Only a single register to load / store. Don't bother.
   unsigned NumRegs = Regs.size();
   if (NumRegs <= 1)
     return false;
 
   // For Thumb1 targets, it might be necessary to clobber the CPSR to merge.
   // Compute liveness information for that register to make the decision.
   bool SafeToClobberCPSR = !isThumb1 ||
     (MBB.computeRegisterLiveness(TRI, ARM::CPSR, std::prev(MBBI), 15) ==
      MachineBasicBlock::LQR_Dead);
 
+  bool Writeback = isThumb1; // Thumb1 LDM/STM have base reg writeback.
+
+  // Exception: If the base register is in the input reglist, Thumb1 LDM is
+  // non-writeback.
+  // It's also not possible to merge an STR of the base register in Thumb1.
+  if (isThumb1)
+    for (unsigned I = 0; I < NumRegs; ++I)
+      if (Base == Regs[I].first) {
+        if (Opcode == ARM::tLDRi) {
+          Writeback = false;
+          break;
+        } else if (Opcode == ARM::tSTRi) {
+          return false;
+        }
+      }
+
   ARM_AM::AMSubMode Mode = ARM_AM::ia;
   // VFP and Thumb2 do not support IB or DA modes. Thumb1 only supports IA.
   bool isNotVFP = isi32Load(Opcode) || isi32Store(Opcode);
   bool haveIBAndDA = isNotVFP && !isThumb2 && !isThumb1;
 
   if (Offset == 4 && haveIBAndDA) {
     Mode = ARM_AM::ib;
   } else if (Offset == -4 * (int)NumRegs + 4 && haveIBAndDA) {
ARMLoadStoreOpt::MergeOps(MachineBasicBlock &MBB,
   bool isDef = (isi32Load(Opcode) || Opcode == ARM::VLDRS ||
                 Opcode == ARM::VLDRD);
 
   // Get LS multiple opcode. Note that for Thumb1 this might be an opcode with
   // base register writeback.
   Opcode = getLoadStoreMultipleOpcode(Opcode, Mode);
   if (!Opcode) return false;
 
-  bool Writeback = isThumb1; // Thumb1 LDM/STM have base reg writeback.
-
-  // Exception: If the base register is in the input reglist, Thumb1 LDM is
-  // non-writeback. Check for this.
-  if (Opcode == ARM::tLDMIA && isThumb1)
-    for (unsigned I = 0; I < NumRegs; ++I)
-      if (Base == Regs[I].first) {
-        Writeback = false;
-        break;
-      }
-
-  // If the merged instruction has writeback and the base register is not killed
-  // it's not safe to do the merge on Thumb1. This is because resetting the base
-  // register writeback by inserting a SUBS sets the condition flags.
-  // FIXME: Try something clever here to see if resetting the base register can
-  // be avoided, e.g. by updating a later ADD/SUB of the base register with the
-  // writeback.
-  if (isThumb1 && Writeback && !BaseKill) return false;
+  // Check if a Thumb1 LDM/STM merge is safe. This is the case if:
+  // - There is no writeback (LDM of base register),
+  // - the base register is killed by the merged instruction,
+  // - or it's safe to overwrite the condition flags, i.e. to insert a SUBS
+  //   to reset the base register.
+  // Otherwise, don't merge.
+  // It's safe to return here since the code to materialize a new base register
+  // above is also conditional on SafeToClobberCPSR.
+  if (isThumb1 && !SafeToClobberCPSR && Writeback && !BaseKill)
+    return false;
 
   MachineInstrBuilder MIB;
 
   if (Writeback) {
     if (Opcode == ARM::tLDMIA)
       // Update tLDMIA with writeback if necessary.
       Opcode = ARM::tLDMIA_UPD;
 
     MIB = BuildMI(MBB, MBBI, dl, TII->get(Opcode));
 
     // Thumb1: we might need to set base writeback when building the MI.
     MIB.addReg(Base, getDefRegState(true))
        .addReg(Base, getKillRegState(BaseKill));
+
+    // The base isn't dead after a merged instruction with writeback.
+    // Insert a sub instruction after the newly formed instruction to reset.
+    if (!BaseKill)
+      UpdateBaseRegUses(MBB, MBBI, dl, Base, NumRegs, Pred, PredReg);
+
   } else {
     // No writeback, simply build the MachineInstr.
     MIB = BuildMI(MBB, MBBI, dl, TII->get(Opcode));
     MIB.addReg(Base, getKillRegState(BaseKill));
   }
 
   MIB.addImm(Pred).addReg(PredReg);
 
for (unsigned i = memOpsBegin; i < memOpsEnd; ++i) {
     }
     MBB.erase(memOps[i].MBBI);
     // Update this memop to refer to the merged instruction.
     // We may need to move kill flags again.
     memOps[i].Merged = true;
     memOps[i].MBBI = Merges.back();
     memOps[i].Position = insertPos;
   }
+
+  // Update memOps offsets, since they may have been modified by MergeOps.
+  for (auto &MemOp : memOps) {
+    MemOp.Offset = getMemoryOpOffset(MemOp.MBBI);
+  }
 }
 
 /// MergeLDR_STR - Merge a number of load / store instructions into one or more
 /// load / store multiple instructions.
 void
 ARMLoadStoreOpt::MergeLDR_STR(MachineBasicBlock &MBB, unsigned SIndex,
                          unsigned Base, int Opcode, unsigned Size,
                          ARMCC::CondCodes Pred, unsigned PredReg,
for (unsigned i = SIndex+1, e = MemOps.size(); i != e; ++i) {
     }
   }
 
   BaseKill =  Loc->killsRegister(Base);
   MergeOpsUpdate(MBB, MemOps, SIndex, MemOps.size(), insertAfter, SOffset,
                  Base, BaseKill, Opcode, Pred, PredReg, Scratch, dl, Merges);
 }
 
-static bool definesCPSR(MachineInstr *MI) {
-  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
-    const MachineOperand &MO = MI->getOperand(i);
-    if (!MO.isReg())
-      continue;
-    if (MO.isDef() && MO.getReg() == ARM::CPSR && !MO.isDead())
-      // If the instruction has live CPSR def, then it's not safe to fold it
-      // into load / store.
-      return true;
-  }
-
-  return false;
-}
-
 static bool isMatchingDecrement(MachineInstr *MI, unsigned Base,
                                 unsigned Bytes, unsigned Limit,
                                 ARMCC::CondCodes Pred, unsigned PredReg) {
   unsigned MyPredReg = 0;
   if (!MI)
     return false;
 
   bool CheckCPSRDef = false;
if (MemOps[i].Position < Position) {
       Loc = MemOps[i].MBBI;
     }
   }
 
   if (Loc != MBB.begin())
     RS->forward(std::prev(Loc));
 }
 
-static int getMemoryOpOffset(const MachineInstr *MI) {
-  int Opcode = MI->getOpcode();
-  bool isAM3 = Opcode == ARM::LDRD || Opcode == ARM::STRD;
-  unsigned NumOperands = MI->getDesc().getNumOperands();
-  unsigned OffField = MI->getOperand(NumOperands-3).getImm();
-
-  if (Opcode == ARM::t2LDRi12 || Opcode == ARM::t2LDRi8 ||
-      Opcode == ARM::t2STRi12 || Opcode == ARM::t2STRi8 ||
-      Opcode == ARM::t2LDRDi8 || Opcode == ARM::t2STRDi8 ||
-      Opcode == ARM::LDRi12   || Opcode == ARM::STRi12)
-    return OffField;
-
-  // Thumb1 immediate offsets are scaled by 4
-  if (Opcode == ARM::tLDRi || Opcode == ARM::tSTRi)
-    return OffField * 4;
-
-  int Offset = isAM3 ? ARM_AM::getAM3Offset(OffField)
-    : ARM_AM::getAM5Offset(OffField) * 4;
-  if (isAM3) {
-    if (ARM_AM::getAM3Op(OffField) == ARM_AM::sub)
-      Offset = -Offset;
-  } else {
-    if (ARM_AM::getAM5Op(OffField) == ARM_AM::sub)
-      Offset = -Offset;
-  }
-  return Offset;
-}
-
 static void InsertLDR_STR(MachineBasicBlock &MBB,
                           MachineBasicBlock::iterator &MBBI,
                           int Offset, bool isDef,
                           DebugLoc dl, unsigned NewOpc,
                           unsigned Reg, bool RegDeadKill, bool RegUndef,
                           unsigned BaseReg, bool BaseKill, bool BaseUndef,
                           bool OffKill, bool OffUndef,
                           ARMCC::CondCodes Pred, unsigned PredReg,

test/CodeGen/Thumb/2014-06-10-thumb1-ldst-opt-bug.ll

 ; RUN: llc < %s -mtriple=thumbv6m-eabi -verify-machineinstrs -o - | FileCheck %s
 
 define void @foo(i32* %A) #0 {
 entry:
 ; CHECK-LABEL: foo:
 ; CHECK: push {r7, lr}
-; CHECK: ldr
-; CHECK-NEXT: ldr
+; CHECK: ldm
+; CHECK-NEXT: subs
 ; CHECK-NEXT: bl
   %0 = load i32* %A, align 4
   %arrayidx1 = getelementptr inbounds i32* %A, i32 1
   %1 = load i32* %arrayidx1, align 4
   tail call void @bar(i32* %A, i32 %0, i32 %1) #2
   ret void
 }
 
 declare void @bar(i32*, i32, i32) #1

test/CodeGen/Thumb/dyn-stackalloc.ll

-; RUN: llc < %s -mtriple=thumb-apple-darwin -disable-cgp-branch-opts -disable-post-ra -verify-machineinstrs | FileCheck %s -check-prefix=CHECK
-; RUN: llc < %s -mtriple=thumb-apple-darwin -disable-cgp-branch-opts -disable-post-ra -regalloc=basic -verify-machineinstrs | FileCheck %s -check-prefix=CHECK
+; RUN: llc < %s -mtriple=thumb-apple-darwin -disable-cgp-branch-opts -disable-post-ra -verify-machineinstrs | FileCheck %s -check-prefix=CHECK -check-prefix=RA_GREEDY
+; RUN: llc < %s -mtriple=thumb-apple-darwin -disable-cgp-branch-opts -disable-post-ra -regalloc=basic -verify-machineinstrs | FileCheck %s -check-prefix=CHECK -check-prefix=RA_BASIC
 
   %struct.state = type { i32, %struct.info*, float**, i32, i32, i32, i32, i32, i32, i32, i32, i32, i64, i64, i64, i64, i64, i64, i8* }
   %struct.info = type { i32, i32, i32, i32, i32, i32, i32, i8* }
 
 define void @t1(%struct.state* %v) {
 ; CHECK-LABEL: t1:
 ; CHECK: push
 ; CHECK: add r7, sp, #12

 
 define void @t2(%struct.comment* %vc, i8* %tag, i8* %contents) {
 ; CHECK-LABEL: t2:
 ; CHECK: push
 ; CHECK: add r7, sp, #12
 ; CHECK: sub sp, #
 ; CHECK: mov r[[R0:[0-9]+]], sp
 ; CHECK: str r{{[0-9+]}}, [r[[R0]]
-; CHECK: str r{{[0-9+]}}, [r[[R0]]
+; RA_GREEDY: str r{{[0-9+]}}, [r[[R0]]
+; RA_BASIC: stm r[[R0]]!
 ; CHECK-NOT: ldr r0, [sp
 ; CHECK: mov r[[R1:[0-9]+]], sp
 ; CHECK: subs r[[R2:[0-9]+]], r[[R1]], r{{[0-9]+}}
 ; CHECK: mov sp, r[[R2]]
 ; CHECK-NOT: ldr r0, [sp
 ; CHECK: bx
   %tmp1 = call i32 @strlen( i8* %tag )
   %tmp3 = call i32 @strlen( i8* %contents )

test/CodeGen/Thumb/thumb-memcpy-ldm-stm.ll

 ; RUN: llc -mtriple=thumbv6m-eabi -verify-machineinstrs %s -o - | FileCheck %s
-
 @d = external global [64 x i32]
 @s = external global [64 x i32]
 
 ; Function Attrs: nounwind
 define void @t1() #0 {
 entry:
 ; CHECK-LABEL: t1:
-; CHECK-NOT: ldm
-; CHECK-NOT: stm
+; CHECK: ldr r[[LB:[0-9]]],
+; CHECK-NEXT: ldm r[[LB]]!,
+; CHECK-NEXT: ldr r[[SB:[0-9]]],
+; CHECK-NEXT: stm r[[SB]]!,
+; CHECK-NEXT: ldrb {{.*}}, [r[[LB]]]
+; CHECK-NEXT: strb {{.*}}, [r[[SB]]]
     tail call void @llvm.memcpy.p0i8.p0i8.i32(i8* bitcast ([64 x i32]* @s to i8*), i8* bitcast ([64 x i32]* @d to i8*), i32 17, i32 4, i1 false)
     ret void
 }
 
 ; Function Attrs: nounwind
 define void @t2() #0 {
 entry:
 ; CHECK-LABEL: t2:
-; CHECK-NOT: ldm
-; CHECK-NOT: stm
+; CHECK: ldr r[[LB:[0-9]]],
+; CHECK-NEXT: ldm r[[LB]]!,
+; CHECK-NEXT: ldr r[[SB:[0-9]]],
+; CHECK-NEXT: stm r[[SB]]!,
+; CHECK-NEXT: ldrh {{.*}}, [r[[LB]]]
+; CHECK-NEXT: ldrb {{.*}}, [r[[LB]], #2]
+; CHECK-NEXT: strb {{.*}}, [r[[SB]], #2]
+; CHECK-NEXT: strh {{.*}}, [r[[SB]]]
     tail call void @llvm.memcpy.p0i8.p0i8.i32(i8* bitcast ([64 x i32]* @s to i8*), i8* bitcast ([64 x i32]* @d to i8*), i32 15, i32 4, i1 false)
     ret void
 }
 
 ; Function Attrs: nounwind
 declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture readonly, i32, i32, i1) #1