[MachineCopyPropagation] Fix a bug with undef handling when the value is actualy...

[oota-llvm.git] / lib / CodeGen / MachineCopyPropagation.cpp

diff --git a/lib/CodeGen/MachineCopyPropagation.cpp b/lib/CodeGen/MachineCopyPropagation.cpp
index 712e7414337de3889776b0d811035296be09d2f3..602c1fa8d00fd0ca15621509dfbec4b6e5be3936 100644 (file)
--- a/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/lib/CodeGen/MachineCopyPropagation.cpp
@@ -11,23 +11,25 @@
 //
 //===----------------------------------------------------------------------===//
 
-#define DEBUG_TYPE "codegen-cp"
 #include "llvm/CodeGen/Passes.h"
-#include "llvm/Pass.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Pass.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
 using namespace llvm;
 
+#define DEBUG_TYPE "codegen-cp"
+
 STATISTIC(NumDeletes, "Number of dead copies deleted");
 
 namespace {
@@ -42,7 +44,7 @@ namespace {
      initializeMachineCopyPropagationPass(*PassRegistry::getPassRegistry());
     }
 
-    virtual bool runOnMachineFunction(MachineFunction &MF);
+    bool runOnMachineFunction(MachineFunction &MF) override;
 
   private:
     typedef SmallVector<unsigned, 4> DestList;
@@ -73,10 +75,9 @@ MachineCopyPropagation::SourceNoLongerAvailable(unsigned Reg,
            I != E; ++I) {
         unsigned MappedDef = *I;
         // Source of copy is no longer available for propagation.
-        if (AvailCopyMap.erase(MappedDef)) {
-          for (MCSubRegIterator SR(MappedDef, TRI); SR.isValid(); ++SR)
-            AvailCopyMap.erase(*SR);
-        }
+        AvailCopyMap.erase(MappedDef);
+        for (MCSubRegIterator SR(MappedDef, TRI); SR.isValid(); ++SR)
+          AvailCopyMap.erase(*SR);
       }
     }
   }
@@ -127,13 +128,10 @@ static bool isNopCopy(MachineInstr *CopyMI, unsigned Def, unsigned Src,
 }
 
 // Remove MI from the function because it has been determined it is dead.
-// Turn it into a noop KILL instruction if it has super-register liveness
-// adjustments.
+// Turn it into a noop KILL instruction as opposed to removing it to
+// maintain imp-use/imp-def chains.
 void MachineCopyPropagation::removeCopy(MachineInstr *MI) {
-  if (MI->getNumOperands() == 2)
-    MI->eraseFromParent();
-  else
-    MI->setDesc(TII->get(TargetOpcode::KILL));
+  MI->setDesc(TII->get(TargetOpcode::KILL));
 }
 
 bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
@@ -142,6 +140,8 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
   DenseMap<unsigned, MachineInstr*> CopyMap;         // Def -> copies map
   SourceMap SrcMap; // Src -> Def map
 
+  DEBUG(dbgs() << "MCP: CopyPropagateBlock " << MBB.getName() << "\n");
+
   bool Changed = false;
   for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); I != E; ) {
     MachineInstr *MI = &*I;
@@ -176,6 +176,8 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
           // CALL
           // %RAX<def> = COPY %RSP
 
+          DEBUG(dbgs() << "MCP: copy is a NOP, removing: "; MI->dump());
+
           // Clear any kills of Def between CopyMI and MI. This extends the
           // live range.
           for (MachineBasicBlock::iterator I = CopyMI, E = MI; I != E; ++I)
@@ -191,10 +193,14 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
       // If Src is defined by a previous copy, it cannot be eliminated.
       for (MCRegAliasIterator AI(Src, TRI, true); AI.isValid(); ++AI) {
         CI = CopyMap.find(*AI);
-        if (CI != CopyMap.end())
+        if (CI != CopyMap.end()) {
+          DEBUG(dbgs() << "MCP: Copy is no longer dead: "; CI->second->dump());
           MaybeDeadCopies.remove(CI->second);
+        }
       }
 
+      DEBUG(dbgs() << "MCP: Copy is a deletion candidate: "; MI->dump());
+
       // Copy is now a candidate for deletion.
       MaybeDeadCopies.insert(MI);
 
@@ -213,9 +219,8 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
         CopyMap.erase(*AI);
         AvailCopyMap.erase(*AI);
       }
-      CopyMap[Def] = MI;
-      AvailCopyMap[Def] = MI;
-      for (MCSubRegIterator SR(Def, TRI); SR.isValid(); ++SR) {
+      for (MCSubRegIterator SR(Def, TRI, /*IncludeSelf=*/true); SR.isValid();
+           ++SR) {
         CopyMap[*SR] = MI;
         AvailCopyMap[*SR] = MI;
       }
@@ -256,9 +261,19 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
       // for elimination.
       for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
         DenseMap<unsigned, MachineInstr*>::iterator CI = CopyMap.find(*AI);
-        if (CI != CopyMap.end())
+        if (CI != CopyMap.end()) {
+          DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());
           MaybeDeadCopies.remove(CI->second);
+        }
       }
+      // Treat undef use like defs for copy propagation but not for
+      // dead copy. We would need to do a liveness check to be sure the copy
+      // is dead for undef uses.
+      // The backends are allowed to do whatever they want with undef value
+      // and we cannot be sure this register will not be rewritten to break
+      // some false dependencies for the hardware for instance.
+      if (MO.isUndef())
+        Defs.push_back(Reg);
     }
 
     // The instruction has a register mask operand which means that it clobbers
@@ -274,6 +289,8 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
         unsigned Reg = (*DI)->getOperand(0).getReg();
         if (MRI->isReserved(Reg) || !MaskMO.clobbersPhysReg(Reg))
           continue;
+        DEBUG(dbgs() << "MCP: Removing copy due to regmask clobbering: ";
+              (*DI)->dump());
         removeCopy(*DI);
         Changed = true;
         ++NumDeletes;
@@ -321,10 +338,13 @@ bool MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
 }
 
 bool MachineCopyPropagation::runOnMachineFunction(MachineFunction &MF) {
+  if (skipOptnoneFunction(*MF.getFunction()))
+    return false;
+
   bool Changed = false;
 
-  TRI = MF.getTarget().getRegisterInfo();
-  TII = MF.getTarget().getInstrInfo();
+  TRI = MF.getSubtarget().getRegisterInfo();
+  TII = MF.getSubtarget().getInstrInfo();
   MRI = &MF.getRegInfo();
 
   for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)