From bb73468e2bfb21160266691e9cdc4c4ea4256b22 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Wed, 5 Oct 2011 00:39:32 +0000
Subject: [PATCH] Look at the number of entries in the jump table and jump to a
 'trap' block if the value exceeds that number.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141143 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelLowering.cpp | 64 +++++++++++++++++++++++-------
 1 file changed, 50 insertions(+), 14 deletions(-)

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index e0c079afcda..c988c4aa0d2 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -5493,11 +5493,9 @@ EmitSjLjDispatchBlock(MachineInstr *MI, MachineBasicBlock *MBB) const {
   ARMFunctionInfo *AFI = MF->getInfo<ARMFunctionInfo>();
   const Function *F = MF->getFunction();
   MachineFrameInfo *MFI = MF->getFrameInfo();
-  MachineBasicBlock *DispatchBB = MF->CreateMachineBasicBlock();
   int FI = MFI->getFunctionContextIndex();
-  MachineBasicBlock *Last = &MF->back();
-  MF->insert(MF->end(), DispatchBB);
-  MF->RenumberBlocks(Last);
+
+  MachineBasicBlock *DispatchBB = MF->CreateMachineBasicBlock();
 
   // Shove the dispatch's address into the return slot in the function context.
   DispatchBB->setIsLandingPad();
@@ -5585,8 +5583,6 @@ EmitSjLjDispatchBlock(MachineInstr *MI, MachineBasicBlock *MBB) const {
                    .addMemOperand(FIMMO));
   }
 
-  MI->eraseFromParent();   // The instruction is gone now.
-
   // Now get a mapping of the call site numbers to all of the landing pads
   // they're associated with.
   DenseMap<unsigned, SmallVector<MachineBasicBlock*, 2> > CallSiteNumToLPad;
@@ -5617,10 +5613,8 @@ EmitSjLjDispatchBlock(MachineInstr *MI, MachineBasicBlock *MBB) const {
   for (unsigned I = 1; I <= MaxCSNum; ++I) {
     SmallVectorImpl<MachineBasicBlock*> &MBBList = CallSiteNumToLPad[I];
     for (SmallVectorImpl<MachineBasicBlock*>::iterator
-           II = MBBList.begin(), IE = MBBList.end(); II != IE; ++II) {
+           II = MBBList.begin(), IE = MBBList.end(); II != IE; ++II)
       LPadList.push_back(*II);
-      DispatchBB->addSuccessor(*II);
-    }
   }
 
   MachineJumpTableInfo *JTI =
@@ -5628,34 +5622,76 @@ EmitSjLjDispatchBlock(MachineInstr *MI, MachineBasicBlock *MBB) const {
   unsigned MJTI = JTI->createJumpTableIndex(LPadList);
   unsigned UId = AFI->createJumpTableUId();
 
-  FIMMO = MF->getMachineMemOperand(MachinePointerInfo::getFixedStack(FI),
-                                   MachineMemOperand::MOLoad, 4, 4);
+  MachineBasicBlock *TrapBB = MF->CreateMachineBasicBlock();
+  BuildMI(TrapBB, dl, TII->get(ARM::TRAP));
+  DispatchBB->addSuccessor(TrapBB);
+
+  MachineBasicBlock *DispContBB = MF->CreateMachineBasicBlock();
+  DispatchBB->addSuccessor(DispContBB);
 
   unsigned NewVReg1 = MRI->createVirtualRegister(TRC);
   AddDefaultPred(BuildMI(DispatchBB, dl, TII->get(ARM::t2LDRi12), NewVReg1)
                  .addFrameIndex(FI)
                  .addImm(4)
                  .addMemOperand(FIMMO));
+  AddDefaultPred(BuildMI(DispatchBB, dl, TII->get(ARM::t2CMPri))
+                 .addReg(NewVReg1)
+                 .addImm(LPadList.size()));
+  BuildMI(DispatchBB, dl, TII->get(ARM::t2Bcc))
+    .addMBB(TrapBB)
+    .addImm(ARMCC::HI)
+    .addReg(ARM::CPSR);
+
+/*
+  %vreg11<def> = t2LDRi12 <fi#0>, 4, pred:14, pred:%noreg; mem:Volatile LD4[%sunkaddr131] rGPR:%vreg11
+  t2CMPri %vreg11, 6, pred:14, pred:%noreg, %CPSR<imp-def>; rGPR:%vreg11
+  t2Bcc <BB#33>, pred:8, pred:%CPSR
+*/
+
+/*
+  %vreg11<def> = t2LDRi12 <fi#0>, 4, pred:14, pred:%noreg; mem:Volatile LD4[%sunkaddr131] rGPR:%vreg11
+  %vreg12<def> = t2LEApcrelJT <jt#0>, 0, pred:14, pred:%noreg; rGPR:%vreg12
+  %vreg13<def> = t2ADDrs %vreg12<kill>, %vreg11, 18, pred:14, pred:%noreg, opt:%noreg; GPRnopc:%vreg13 rGPR:%vreg12,%vreg11
+  t2BR_JT %vreg13<kill>, %vreg11, <jt#0>, 0; GPRnopc:%vreg13 rGPR:%vreg11
+*/
+
+  FIMMO = MF->getMachineMemOperand(MachinePointerInfo::getFixedStack(FI),
+                                   MachineMemOperand::MOLoad, 4, 4);
 
   unsigned NewVReg2 = MRI->createVirtualRegister(TRC);
-  AddDefaultPred(BuildMI(DispatchBB, dl, TII->get(ARM::t2LEApcrelJT), NewVReg2)
+  AddDefaultPred(BuildMI(DispContBB, dl, TII->get(ARM::t2LEApcrelJT), NewVReg2)
                  .addJumpTableIndex(MJTI)
                  .addImm(UId));
 
   unsigned NewVReg3 = MRI->createVirtualRegister(TRC);
   AddDefaultCC(
     AddDefaultPred(
-      BuildMI(DispatchBB, dl, TII->get(ARM::t2ADDrs), NewVReg3)
+      BuildMI(DispContBB, dl, TII->get(ARM::t2ADDrs), NewVReg3)
       .addReg(NewVReg2, RegState::Kill)
       .addReg(NewVReg1)
       .addImm(18)));
 
-  BuildMI(DispatchBB, dl, TII->get(ARM::t2BR_JT))
+  BuildMI(DispContBB, dl, TII->get(ARM::t2BR_JT))
     .addReg(NewVReg3, RegState::Kill)
     .addReg(NewVReg1)
     .addJumpTableIndex(MJTI)
     .addImm(UId);
 
+  // Add the jump table entries as successors to the MBB.
+  for (std::vector<MachineBasicBlock*>::iterator
+         I = LPadList.begin(), E = LPadList.end(); I != E; ++I)
+    DispContBB->addSuccessor(*I);
+
+  // Insert and renumber MBBs.
+  MachineBasicBlock *Last = &MF->back();
+  MF->insert(MF->end(), DispatchBB);
+  MF->insert(MF->end(), DispContBB);
+  MF->insert(MF->end(), TrapBB);
+  MF->RenumberBlocks(Last);
+
+  // The instruction is gone now.
+  MI->eraseFromParent();
+
   return MBB;
 }