[SystemZ] Handle DBG_VALUE instructions in two places in backend.

Two backend optimizations failed to handle cases when compiled with -g, due
to failing to consider DBG_VALUE instructions. This was in
SystemZTargetLowering::emitSelect() and
SystemZElimCompare::getRegReferences().

This patch makes sure that DBG_VALUEs are recognized so that they do not
affect these optimizations.

Tests for branch-on-count, load-and-trap and consecutive selects.

Review: Ulrich Weigand
https://reviews.llvm.org/D57048

llvm-svn: 351928

2 files changed, 10 insertions, 6 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp b/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
index 0028ae7eb6f..4c13cd6bfca 100644
--- a/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZElimCompare.cpp
@@ -146,6 +146,9 @@ static bool resultTests(MachineInstr &MI, unsigned Reg) {
 // Describe the references to Reg or any of its aliases in MI.
 Reference SystemZElimCompare::getRegReferences(MachineInstr &MI, unsigned Reg) {
   Reference Ref;
+  if (MI.isDebugInstr())
+    return Ref;
+
   for (unsigned I = 0, E = MI.getNumOperands(); I != E; ++I) {
     const MachineOperand &MO = MI.getOperand(I);
     if (MO.isReg()) {
diff --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
index 0b814ccac3a..0c41f38554f 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -6212,7 +6212,8 @@ static void createPHIsForSelects(MachineBasicBlock::iterator MIItBegin,
   // destination registers, and the registers that went into the PHI.
   DenseMap<unsigned, std::pair<unsigned, unsigned>> RegRewriteTable;
 
-  for (MachineBasicBlock::iterator MIIt = MIItBegin; MIIt != MIItEnd; ++MIIt) {
+  for (MachineBasicBlock::iterator MIIt = MIItBegin; MIIt != MIItEnd;
+       MIIt = skipDebugInstructionsForward(++MIIt, MIItEnd)) {
     unsigned DestReg = MIIt->getOperand(0).getReg();
     unsigned TrueReg = MIIt->getOperand(1).getReg();
     unsigned FalseReg = MIIt->getOperand(2).getReg();
@@ -6253,8 +6254,8 @@ SystemZTargetLowering::emitSelect(MachineInstr &MI,
   // same condition code value, we want to expand all of them into
   // a single pair of basic blocks using the same condition.
   MachineInstr *LastMI = &MI;
-  MachineBasicBlock::iterator NextMIIt =
-      std::next(MachineBasicBlock::iterator(MI));
+  MachineBasicBlock::iterator NextMIIt = skipDebugInstructionsForward(
+      std::next(MachineBasicBlock::iterator(MI)), MBB->end());
 
   if (isSelectPseudo(MI))
     while (NextMIIt != MBB->end() && isSelectPseudo(*NextMIIt) &&
@@ -6262,7 +6263,7 @@ SystemZTargetLowering::emitSelect(MachineInstr &MI,
            (NextMIIt->getOperand(4).getImm() == CCMask ||
             NextMIIt->getOperand(4).getImm() == (CCValid ^ CCMask))) {
       LastMI = &*NextMIIt;
-      ++NextMIIt;
+      NextMIIt = skipDebugInstructionsForward(++NextMIIt, MBB->end());
     }
 
   MachineBasicBlock *StartMBB = MBB;
@@ -6295,8 +6296,8 @@ SystemZTargetLowering::emitSelect(MachineInstr &MI,
   //  ...
   MBB = JoinMBB;
   MachineBasicBlock::iterator MIItBegin = MachineBasicBlock::iterator(MI);
-  MachineBasicBlock::iterator MIItEnd =
-      std::next(MachineBasicBlock::iterator(LastMI));
+  MachineBasicBlock::iterator MIItEnd = skipDebugInstructionsForward(
+      std::next(MachineBasicBlock::iterator(LastMI)), MBB->end());
   createPHIsForSelects(MIItBegin, MIItEnd, StartMBB, FalseMBB, MBB);
 
   StartMBB->erase(MIItBegin, MIItEnd);