Where the BranchFolding pass removes a branch then adds another better branch,

the DebugLoc information can be maintained throughout by grabbing the DebugLoc
before the RemoveBranch and then passing the result to the InsertBranch.
Patch by Andrew Stanford-Jason!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152212 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 59c92b3..f57f4a8 100644 (file)
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -1019,12 +1019,27 @@ static bool IsBetterFallthrough(MachineBasicBlock *MBB1,
   return MBB2I->isCall() && !MBB1I->isCall();
 }
 
+/// getBranchDebugLoc - Find and return, if any, the DebugLoc of the branch
+/// instructions on the block. Always use the DebugLoc of the first
+/// branching instruction found unless its absent, in which case use the
+/// DebugLoc of the second if present.
+static DebugLoc getBranchDebugLoc(MachineBasicBlock &MBB) {
+  MachineBasicBlock::iterator I = MBB.end();
+  if (I == MBB.begin())
+    return DebugLoc();
+  --I;
+  while (I->isDebugValue() && I != MBB.begin())
+    --I;
+  if (I->isBranch())
+    return I->getDebugLoc();
+  return DebugLoc();
+}
+
 /// OptimizeBlock - Analyze and optimize control flow related to the specified
 /// block.  This is never called on the entry block.
 bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
   bool MadeChange = false;
   MachineFunction &MF = *MBB->getParent();
-  DebugLoc dl;  // FIXME: this is nowhere
 ReoptimizeBlock:
 
   MachineFunction::iterator FallThrough = MBB;
@@ -1073,6 +1088,7 @@ ReoptimizeBlock:
     // destination, remove the branch, replacing it with an unconditional one or
     // a fall-through.
     if (PriorTBB && PriorTBB == PriorFBB) {
+      DebugLoc dl = getBranchDebugLoc(PrevBB);
       TII->RemoveBranch(PrevBB);
       PriorCond.clear();
       if (PriorTBB != MBB)
@@ -1130,6 +1146,7 @@ ReoptimizeBlock:
     // If the prior block branches somewhere else on the condition and here if
     // the condition is false, remove the uncond second branch.
     if (PriorFBB == MBB) {
+      DebugLoc dl = getBranchDebugLoc(PrevBB);
       TII->RemoveBranch(PrevBB);
       TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond, dl);
       MadeChange = true;
@@ -1143,6 +1160,7 @@ ReoptimizeBlock:
     if (PriorTBB == MBB) {
       SmallVector<MachineOperand, 4> NewPriorCond(PriorCond);
       if (!TII->ReverseBranchCondition(NewPriorCond)) {
+        DebugLoc dl = getBranchDebugLoc(PrevBB);
         TII->RemoveBranch(PrevBB);
         TII->InsertBranch(PrevBB, PriorFBB, 0, NewPriorCond, dl);
         MadeChange = true;
@@ -1180,6 +1198,7 @@ ReoptimizeBlock:
           DEBUG(dbgs() << "\nMoving MBB: " << *MBB
                        << "To make fallthrough to: " << *PriorTBB << "\n");
 
+          DebugLoc dl = getBranchDebugLoc(PrevBB);
           TII->RemoveBranch(PrevBB);
           TII->InsertBranch(PrevBB, MBB, 0, NewPriorCond, dl);
 
@@ -1209,6 +1228,7 @@ ReoptimizeBlock:
     if (CurTBB && CurFBB && CurFBB == MBB && CurTBB != MBB) {
       SmallVector<MachineOperand, 4> NewCond(CurCond);
       if (!TII->ReverseBranchCondition(NewCond)) {
+        DebugLoc dl = getBranchDebugLoc(*MBB);
         TII->RemoveBranch(*MBB);
         TII->InsertBranch(*MBB, CurFBB, CurTBB, NewCond, dl);
         MadeChange = true;
@@ -1222,6 +1242,7 @@ ReoptimizeBlock:
     if (CurTBB && CurCond.empty() && CurFBB == 0 &&
         IsBranchOnlyBlock(MBB) && CurTBB != MBB &&
         !MBB->hasAddressTaken()) {
+      DebugLoc dl = getBranchDebugLoc(*MBB);
       // This block may contain just an unconditional branch.  Because there can
       // be 'non-branch terminators' in the block, try removing the branch and
       // then seeing if the block is empty.
@@ -1264,8 +1285,9 @@ ReoptimizeBlock:
               assert(PriorFBB == 0 && "Machine CFG out of date!");
               PriorFBB = MBB;
             }
+            DebugLoc pdl = getBranchDebugLoc(PrevBB);
             TII->RemoveBranch(PrevBB);
-            TII->InsertBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, dl);
+            TII->InsertBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, pdl);
           }
 
           // Iterate through all the predecessors, revectoring each in-turn.
@@ -1289,9 +1311,10 @@ ReoptimizeBlock:
               bool NewCurUnAnalyzable = TII->AnalyzeBranch(*PMBB, NewCurTBB,
                       NewCurFBB, NewCurCond, true);
               if (!NewCurUnAnalyzable && NewCurTBB && NewCurTBB == NewCurFBB) {
+                DebugLoc pdl = getBranchDebugLoc(*PMBB);
                 TII->RemoveBranch(*PMBB);
                 NewCurCond.clear();
-                TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond, dl);
+                TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond, pdl);
                 MadeChange = true;
                 ++NumBranchOpts;
                 PMBB->CorrectExtraCFGEdges(NewCurTBB, 0, false);
@@ -1351,7 +1374,7 @@ ReoptimizeBlock:
           if (CurFallsThru) {
             MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
             CurCond.clear();
-            TII->InsertBranch(*MBB, NextBB, 0, CurCond, dl);
+            TII->InsertBranch(*MBB, NextBB, 0, CurCond, DebugLoc());
           }
           MBB->moveAfter(PredBB);
           MadeChange = true;