[llvm] r276910 - Codegen: IfConversion: Factor out a function to count dup instrs.

[Kyle Butt via llvm-commits]

Author: iteratee
Date: Wed Jul 27 15:19:33 2016
New Revision: 276910

URL: http://llvm.org/viewvc/llvm-project?rev=276910&view=rev
Log:
Codegen: IfConversion: Factor out a function to count dup instrs.

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.

Modified:
    llvm/trunk/lib/CodeGen/IfConversion.cpp

Modified: llvm/trunk/lib/CodeGen/IfConversion.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/IfConversion.cpp?rev=276910&r1=276909&r2=276910&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/IfConversion.cpp (original)
+++ llvm/trunk/lib/CodeGen/IfConversion.cpp Wed Jul 27 15:19:33 2016
@@ -540,39 +540,15 @@ bool IfConverter::ValidTriangle(BBInfo &
   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;
+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) {
 
-  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 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()) {
@@ -601,20 +577,27 @@ bool IfConverter::ValidDiamond(BBInfo &T
   // 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()) {
-    while (TIE != TIB && TIE->isBranch())
-      --TIE;
-    while (FIE != FIB && FIE->isBranch())
-      --FIE;
+  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) {
@@ -633,11 +616,52 @@ bool IfConverter::ValidDiamond(BBInfo &T
     }
     if (!TIE->isIdenticalTo(*FIE))
       break;
-    ++Dups2;
+    // 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;
 }