1 files changed, 28 insertions, 13 deletions

diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp
index ce264eeef9..29405eb65d 100644
--- a/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -275,6 +275,7 @@ namespace {
 
   private:
     void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
+    bool BBHasFallthrough(MachineBasicBlock *MBB);
     CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
     unsigned getCPELogAlign(const MachineInstr *CPEMI);
     void scanFunctionJumpTables();
@@ -382,7 +383,9 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &mf) {
                << MCP->getConstants().size() << " CP entries, aligned to "
                << MCP->getConstantPoolAlignment() << " bytes *****\n");
 
-  TII = (const ARMBaseInstrInfo*)MF->getTarget().getInstrInfo();
+  TII = (const ARMBaseInstrInfo *)MF->getTarget()
+            .getSubtargetImpl()
+            ->getInstrInfo();
   AFI = MF->getInfo<ARMFunctionInfo>();
   STI = &MF->getTarget().getSubtarget<ARMSubtarget>();
 
@@ -529,7 +532,7 @@ ARMConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
   // identity mapping of CPI's to CPE's.
   const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
 
-  const DataLayout &TD = *MF->getTarget().getDataLayout();
+  const DataLayout &TD = *MF->getSubtarget().getDataLayout();
   for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
     unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
     assert(Size >= 4 && "Too small constant pool entry");
@@ -554,9 +557,7 @@ ARMConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
         InsPoint[a] = CPEMI;
 
     // Add a new CPEntry, but no corresponding CPUser yet.
-    std::vector<CPEntry> CPEs;
-    CPEs.push_back(CPEntry(CPEMI, i));
-    CPEntries.push_back(CPEs);
+    CPEntries.emplace_back(1, CPEntry(CPEMI, i));
     ++NumCPEs;
     DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
                  << Size << ", align = " << Align <<'\n');
@@ -566,7 +567,7 @@ ARMConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
 
 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
 /// into the block immediately after it.
-static bool BBHasFallthrough(MachineBasicBlock *MBB) {
+bool ARMConstantIslands::BBHasFallthrough(MachineBasicBlock *MBB) {
   // Get the next machine basic block in the function.
   MachineFunction::iterator MBBI = MBB;
   // Can't fall off end of function.
@@ -574,12 +575,15 @@ static bool BBHasFallthrough(MachineBasicBlock *MBB) {
     return false;
 
   MachineBasicBlock *NextBB = std::next(MBBI);
-  for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
-       E = MBB->succ_end(); I != E; ++I)
-    if (*I == NextBB)
-      return true;
+  if (std::find(MBB->succ_begin(), MBB->succ_end(), NextBB) == MBB->succ_end())
+    return false;
 
-  return false;
+  // Try to analyze the end of the block. A potential fallthrough may already
+  // have an unconditional branch for whatever reason.
+  MachineBasicBlock *TBB, *FBB;
+  SmallVector<MachineOperand, 4> Cond;
+  bool TooDifficult = TII->AnalyzeBranch(*MBB, TBB, FBB, Cond);
+  return TooDifficult || FBB == nullptr;
 }
 
 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
@@ -1203,7 +1207,8 @@ bool ARMConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
     unsigned Growth;
     if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
         (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
-         NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
+         NewWaterList.count(WaterBB) || WaterBB == U.MI->getParent()) &&
+        Growth < BestGrowth) {
       // This is the least amount of required padding seen so far.
       BestGrowth = Growth;
       WaterIter = IP;
@@ -1309,7 +1314,12 @@ void ARMConstantIslands::createNewWater(unsigned CPUserIndex,
   // Back past any possible branches (allow for a conditional and a maximally
   // long unconditional).
   if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
-    BaseInsertOffset = UserBBI.postOffset() - UPad - 8;
+    // Ensure BaseInsertOffset is larger than the offset of the instruction
+    // following UserMI so that the loop which searches for the split point
+    // iterates at least once.
+    BaseInsertOffset =
+        std::max(UserBBI.postOffset() - UPad - 8,
+                 UserOffset + TII->GetInstSizeInBytes(UserMI) + 1);
     DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
   }
   unsigned EndInsertOffset = BaseInsertOffset + 4 + UPad +
@@ -1352,6 +1362,11 @@ void ARMConstantIslands::createNewWater(unsigned CPUserIndex,
     if (CC != ARMCC::AL)
       MI = LastIT;
   }
+
+  // We really must not split an IT block.
+  DEBUG(unsigned PredReg;
+        assert(!isThumb || getITInstrPredicate(MI, PredReg) == ARMCC::AL));
+
   NewMBB = splitBlockBeforeInstr(MI);
 }