Let each target determines whether a machine instruction is dead. If true, that allows late codeine passes to delete it.

This is considered a workaround. The problem is some targets are not modeling side effects correctly. PPC is apparently one of those. This patch allows ppc llvm-gcc to bootstrap on Darwin. Once we find out which instruction definitions are wrong, we can remove the PPCInstrInfo workaround.

llvm-svn: 76703

1 files changed, 2 insertions, 25 deletions

diff --git a/llvm/lib/CodeGen/VirtRegRewriter.cpp b/llvm/lib/CodeGen/VirtRegRewriter.cpp
index 83224cc4742..745bfca9f26 100644
--- a/llvm/lib/CodeGen/VirtRegRewriter.cpp
+++ b/llvm/lib/CodeGen/VirtRegRewriter.cpp
@@ -1349,29 +1349,6 @@ private:
     ++NumStores;
   }
 
-  /// isSafeToDelete - Return true if this instruction doesn't produce any side
-  /// effect and all of its defs are dead.
-  static bool isSafeToDelete(MachineInstr &MI) {
-    const TargetInstrDesc &TID = MI.getDesc();
-    if (TID.mayLoad() || TID.mayStore() || TID.isCall() || TID.isTerminator() ||
-        TID.isCall() || TID.isBarrier() || TID.isReturn() ||
-        TID.hasUnmodeledSideEffects())
-      return false;
-    for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
-      MachineOperand &MO = MI.getOperand(i);
-      if (!MO.isReg() || !MO.getReg())
-        continue;
-      if (MO.isDef() && !MO.isDead())
-        return false;
-      if (MO.isUse() && MO.isKill())
-        // FIXME: We can't remove kill markers or else the scavenger will assert.
-        // An alternative is to add a ADD pseudo instruction to replace kill
-        // markers.
-        return false;
-    }
-    return true;
-  }
-
   /// TransferDeadness - A identity copy definition is dead and it's being
   /// removed. Find the last def or use and mark it as dead / kill.
   void TransferDeadness(MachineBasicBlock *MBB, unsigned CurDist,
@@ -1413,7 +1390,7 @@ private:
       if (LastUD->isDef()) {
         // If the instruction has no side effect, delete it and propagate
         // backward further. Otherwise, mark is dead and we are done.
-        if (!isSafeToDelete(*LastUDMI)) {
+        if (!TII->isDeadInstruction(LastUDMI)) {
           LastUD->setIsDead();
           break;
         }
@@ -2198,7 +2175,7 @@ private:
       }
     ProcessNextInst:
       // Delete dead instructions without side effects.
-      if (!Erased && !BackTracked && isSafeToDelete(MI)) {
+      if (!Erased && !BackTracked && TII->isDeadInstruction(&MI)) {
         InvalidateKills(MI, TRI, RegKills, KillOps);
         VRM.RemoveMachineInstrFromMaps(&MI);
         MBB.erase(&MI);