1 files changed, 41 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 3b3e7a4..dcfd9aa 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -2083,22 +2083,55 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
   if (TBB == FBB) {
     MBB->splice(Loc, TBB, TBB->begin(), TIB);
   } else {
+    // Merge the debug locations, and hoist and kill the debug instructions from
+    // both branches. FIXME: We could probably try harder to preserve some debug
+    // instructions (but at least this isn't producing wrong locations).
+    MachineInstrBuilder MIRBuilder(*MBB->getParent(), Loc);
+    auto HoistAndKillDbgInstr = [MBB, Loc](MachineBasicBlock::iterator DI) {
+      assert(DI->isDebugInstr() && "Expected a debug instruction");
+      if (DI->isDebugRef()) {
+        const TargetInstrInfo *TII =
+            MBB->getParent()->getSubtarget().getInstrInfo();
+        const MCInstrDesc &DBGV = TII->get(TargetOpcode::DBG_VALUE);
+        DI = BuildMI(*MBB->getParent(), DI->getDebugLoc(), DBGV, false, 0,
+                     DI->getDebugVariable(), DI->getDebugExpression());
+        MBB->insert(Loc, &*DI);
+        return;
+      }
+      // Deleting a DBG_PHI results in an undef at the referenced DBG_INSTR_REF.
+      if (DI->isDebugPHI()) {
+        DI->eraseFromParent();
+        return;
+      }
+      // Move DBG_LABELs without modifying them. Set DBG_VALUEs undef.
+      if (!DI->isDebugLabel())
+        DI->setDebugValueUndef();
+      DI->moveBefore(&*Loc);
+    };
+
     // TIB and FIB point to the end of the regions to hoist/merge in TBB and
     // FBB.
     MachineBasicBlock::iterator FE = FIB;
     MachineBasicBlock::iterator FI = FBB->begin();
     for (MachineBasicBlock::iterator TI :
          make_early_inc_range(make_range(TBB->begin(), TIB))) {
-      // Move debug instructions and pseudo probes without modifying them.
-      // FIXME: This is the wrong thing to do for debug locations, which
-      // should at least be killed (and hoisted from BOTH blocks).
-      if (TI->isDebugOrPseudoInstr()) {
-        TI->moveBefore(&*Loc);
+      // Hoist and kill debug instructions from FBB. After this loop FI points
+      // to the next non-debug instruction to hoist (checked in assert after the
+      // TBB debug instruction handling code).
+      while (FI != FE && FI->isDebugInstr())
+        HoistAndKillDbgInstr(FI++);
+
+      // Kill debug instructions before moving.
+      if (TI->isDebugInstr()) {
+        HoistAndKillDbgInstr(TI);
         continue;
       }
 
-      // Get the next non-meta instruction in FBB.
-      FI = skipDebugInstructionsForward(FI, FE, false);
+      // FI and TI now point to identical non-debug instructions.
+      assert(FI != FE && "Unexpected end of FBB range");
+      // Pseudo probes are excluded from the range when identifying foldable
+      // instructions, so we don't expect to see one now.
+      assert(!TI->isPseudoProbe() && "Unexpected pseudo probe in range");
       // NOTE: The loop above checks CheckKillDead but we can't do that here as
       // it modifies some kill markers after the check.
       assert(TI->isIdenticalTo(*FI, MachineInstr::CheckDefs) &&
@@ -2111,6 +2144,7 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
       ++FI;
     }
   }
+
   FBB->erase(FBB->begin(), FIB);
 
   if (UpdateLiveIns)