Codegen: IfConversion: Factor out a function to count dup instrs.

[iteratee]

Summary

Factor out countDuplicatedInstructions to Count duplicated instructions at the
beginning and end of a diamond pattern. This is in prep for adding support for
diamonds that need to be tail-merged.

[iteratee]

Add blank line between functions.

[davidxl]

lgtm

lib/CodeGen/IfConversion.cpp

if (!TExit && blockAlwaysFallThrough(TrueBBI)) {
     MachineFunction::iterator I = TrueBBI.BB->getIterator();
     if (++I == TrueBBI.BB->getParent()->end())
       return false;
     TExit = &*I;
   }
   return TExit && TExit == FalseBBI.BB;
 }
 
-/// ValidDiamond - Returns true if the 'true' and 'false' blocks (along
-/// with their common predecessor) forms a valid diamond shape for ifcvt.
-bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
-                               unsigned &Dups1, unsigned &Dups2) const {
-  Dups1 = Dups2 = 0;
-  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone ||
-      FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone)
-    return false;
-
-  MachineBasicBlock *TT = TrueBBI.TrueBB;
-  MachineBasicBlock *FT = FalseBBI.TrueBB;
-
-  if (!TT && blockAlwaysFallThrough(TrueBBI))
-    TT = getNextBlock(TrueBBI.BB);
-  if (!FT && blockAlwaysFallThrough(FalseBBI))
-    FT = getNextBlock(FalseBBI.BB);
-  if (TT != FT)
-    return false;
-  if (!TT && (TrueBBI.IsBrAnalyzable || FalseBBI.IsBrAnalyzable))
-    return false;
-  if  (TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1)
-    return false;
-
-  // FIXME: Allow true block to have an early exit?
-  if (TrueBBI.FalseBB || FalseBBI.FalseBB ||
-      (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred))
-    return false;
+static void countDuplicatedInstructions(
+    MachineBasicBlock::iterator &TIB,
+    MachineBasicBlock::iterator &FIB,
+    MachineBasicBlock::iterator &TIE,
+    MachineBasicBlock::iterator &FIE,
+    unsigned &Dups1, unsigned &Dups2,
+    MachineBasicBlock &TBB, MachineBasicBlock &FBB,
+    bool SkipConditionalBranches) {
 
-  // Count duplicate instructions at the beginning of the true and false blocks.
-  MachineBasicBlock::iterator TIB = TrueBBI.BB->begin();
-  MachineBasicBlock::iterator FIB = FalseBBI.BB->begin();
-  MachineBasicBlock::iterator TIE = TrueBBI.BB->end();
-  MachineBasicBlock::iterator FIE = FalseBBI.BB->end();
   while (TIB != TIE && FIB != FIE) {
     // Skip dbg_value instructions. These do not count.
     if (TIB->isDebugValue()) {
       while (TIB != TIE && TIB->isDebugValue())
         ++TIB;
       if (TIB == TIE)
         break;
     }
static void countDuplicatedInstructions(
 
   // Now, in preparation for counting duplicate instructions at the ends of the
   // blocks, move the end iterators up past any branch instructions.
   // If both blocks are returning don't skip the branches, since they will
   // likely be both identical return instructions. In such cases the return
   // can be left unpredicated.
   // Check for already containing all of the block.
   if (TIB == TIE || FIB == FIE)
-    return true;
+    return;
   --TIE;
   --FIE;
-  if (!TrueBBI.BB->succ_empty() || !FalseBBI.BB->succ_empty()) {
+  if (!TBB.succ_empty() || !FBB.succ_empty()) {
+    if (SkipConditionalBranches) {
       while (TIE != TIB && TIE->isBranch())
         --TIE;
       while (FIE != FIB && FIE->isBranch())
         --FIE;
+    } else {
+      while (TIE != TIB && TIE->isUnconditionalBranch())
+        --TIE;
+      while (FIE != FIB && FIE->isUnconditionalBranch())
+        --FIE;
+    }
   }
 
   // If Dups1 includes all of a block, then don't count duplicate
   // instructions at the end of the blocks.
   if (TIB == TIE || FIB == FIE)
-    return true;
+    return;
 
   // Count duplicate instructions at the ends of the blocks.
   while (TIE != TIB && FIE != FIB) {
     // Skip dbg_value instructions. These do not count.
     if (TIE->isDebugValue()) {
       while (TIE != TIB && TIE->isDebugValue())
         --TIE;
       if (TIE == TIB)
         break;
     }
     if (FIE->isDebugValue()) {
       while (FIE != FIB && FIE->isDebugValue())
         --FIE;
       if (FIE == FIB)
         break;
     }
     if (!TIE->isIdenticalTo(*FIE))
       break;
+    // If we are trying to make sure the conditional branches are the same, we
+    // still don't want to count them.
+    if (SkipConditionalBranches || !TIE->isBranch())
       ++Dups2;
     --TIE;
     --FIE;
   }
+}
+
+/// ValidDiamond - Returns true if the 'true' and 'false' blocks (along
+/// with their common predecessor) forms a valid diamond shape for ifcvt.
+bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
+                               unsigned &Dups1, unsigned &Dups2) const {
+  Dups1 = Dups2 = 0;
+  if (TrueBBI.IsBeingAnalyzed || TrueBBI.IsDone ||
+      FalseBBI.IsBeingAnalyzed || FalseBBI.IsDone)
+    return false;
+
+  MachineBasicBlock *TT = TrueBBI.TrueBB;
+  MachineBasicBlock *FT = FalseBBI.TrueBB;
+
+  if (!TT && blockAlwaysFallThrough(TrueBBI))
+    TT = getNextBlock(TrueBBI.BB);
+  if (!FT && blockAlwaysFallThrough(FalseBBI))
+    FT = getNextBlock(FalseBBI.BB);
+  if (TT != FT)
+    return false;
+  if (!TT && (TrueBBI.IsBrAnalyzable || FalseBBI.IsBrAnalyzable))
+    return false;
+  if  (TrueBBI.BB->pred_size() > 1 || FalseBBI.BB->pred_size() > 1)
+    return false;
 
+  // FIXME: Allow true block to have an early exit?
+  if (TrueBBI.FalseBB || FalseBBI.FalseBB ||
+      (TrueBBI.ClobbersPred && FalseBBI.ClobbersPred))
+    return false;
+
+  // Count duplicate instructions at the beginning and end of the true and
+  // false blocks.
+  MachineBasicBlock::iterator TIB = TrueBBI.BB->begin();
+  MachineBasicBlock::iterator FIB = FalseBBI.BB->begin();
+  MachineBasicBlock::iterator TIE = TrueBBI.BB->end();
+  MachineBasicBlock::iterator FIE = FalseBBI.BB->end();
+  countDuplicatedInstructions(TIB, FIB, TIE, FIE, Dups1, Dups2,
+                              *TrueBBI.BB, *FalseBBI.BB,
+                              /* SkipConditionalBranches */ true);
   return true;
 }
 
 /// ScanInstructions - Scan all the instructions in the block to determine if
 /// the block is predicable. In most cases, that means all the instructions
 /// in the block are isPredicable(). Also checks if the block contains any
 /// instruction which can clobber a predicate (e.g. condition code register).
 /// If so, the block is not predicable unless it's the last instruction.