ARM: allow constpool entry to be moved to the user's block in all cases.

[oota-llvm.git] / lib / Target / ARM / ARMConstantIslandPass.cpp

diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp
index fa9bfa2b327c324adb73d701b75622f53dfd3fdd..29405eb65d52757aaa14541ef4adac4d2637e6f3 100644 (file)
--- 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();
@@ -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;
@@ -1357,6 +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);
 }