[ARMv8] Prevent generation of deprecated IT blocks on ARMv8 in Thumb mode.

IT blocks can only be one instruction lonf, and can only contain a subset of
the 16 instructions.

Patch by Artyom Skrobov!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190309 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 121 insertions, 36 deletions

diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 62e80632c7..696d039e74 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -513,6 +513,74 @@ bool ARMBaseInstrInfo::DefinesPredicate(MachineInstr *MI,
   return Found;
 }
 
+static bool isV8EligibleForIT(MachineInstr *MI) {
+  switch (MI->getOpcode()) {
+  default:
+    return false;
+  case ARM::tADC:
+  case ARM::tADDi3:
+  case ARM::tADDi8:
+  case ARM::tADDrSPi:
+  case ARM::tADDrr:
+  case ARM::tAND:
+  case ARM::tASRri:
+  case ARM::tASRrr:
+  case ARM::tBIC:
+  case ARM::tCMNz:
+  case ARM::tCMPi8:
+  case ARM::tCMPr:
+  case ARM::tEOR:
+  case ARM::tLDRBi:
+  case ARM::tLDRBr:
+  case ARM::tLDRHi:
+  case ARM::tLDRHr:
+  case ARM::tLDRSB:
+  case ARM::tLDRSH:
+  case ARM::tLDRi:
+  case ARM::tLDRr:
+  case ARM::tLDRspi:
+  case ARM::tLSLri:
+  case ARM::tLSLrr:
+  case ARM::tLSRri:
+  case ARM::tLSRrr:
+  case ARM::tMOVi8:
+  case ARM::tMUL:
+  case ARM::tMVN:
+  case ARM::tORR:
+  case ARM::tROR:
+  case ARM::tRSB:
+  case ARM::tSBC:
+  case ARM::tSTRBi:
+  case ARM::tSTRBr:
+  case ARM::tSTRHi:
+  case ARM::tSTRHr:
+  case ARM::tSTRi:
+  case ARM::tSTRr:
+  case ARM::tSTRspi:
+  case ARM::tSUBi3:
+  case ARM::tSUBi8:
+  case ARM::tSUBrr:
+  case ARM::tTST:
+    return true;
+// there are some "conditionally deprecated" opcodes
+  case ARM::tADDspr:
+    return MI->getOperand(2).getReg() != ARM::PC;
+  case ARM::tADDrSP:
+  case ARM::tBX:
+  case ARM::tBLXr:
+  // ADD PC, SP and BLX PC were always unpredictable,
+  // now on top of it they're deprecated
+    return MI->getOperand(0).getReg() != ARM::PC;
+  case ARM::tADDhirr:
+    return MI->getOperand(0).getReg() != ARM::PC &&
+           MI->getOperand(2).getReg() != ARM::PC;
+  case ARM::tCMPhir:
+  case ARM::tMOVr:
+    return MI->getOperand(0).getReg() != ARM::PC &&
+           MI->getOperand(1).getReg() != ARM::PC;
+  }
+}
+
 /// isPredicable - Return true if the specified instruction can be predicated.
 /// By default, this returns true for every instruction with a
 /// PredicateOperand.
@@ -520,11 +588,17 @@ bool ARMBaseInstrInfo::isPredicable(MachineInstr *MI) const {
   if (!MI->isPredicable())
     return false;
 
-  if ((MI->getDesc().TSFlags & ARMII::DomainMask) == ARMII::DomainNEON) {
-    ARMFunctionInfo *AFI =
-      MI->getParent()->getParent()->getInfo<ARMFunctionInfo>();
-    return AFI->isThumb2Function();
+  ARMFunctionInfo *AFI =
+    MI->getParent()->getParent()->getInfo<ARMFunctionInfo>();
+
+  if (AFI->isThumb2Function()) {
+    if (getSubtarget().hasV8Ops())
+      return isV8EligibleForIT(MI);
+  } else { // non-Thumb
+    if ((MI->getDesc().TSFlags & ARMII::DomainMask) == ARMII::DomainNEON)
+      return false;
   }
+
   return true;
 }
 
diff --git a/lib/Target/ARM/ARMFastISel.cpp b/lib/Target/ARM/ARMFastISel.cpp
index 3cbb9a8185..f3a74c7109 100644
--- a/lib/Target/ARM/ARMFastISel.cpp
+++ b/lib/Target/ARM/ARMFastISel.cpp
@@ -254,10 +254,10 @@ bool ARMFastISel::DefinesOptionalPredicate(MachineInstr *MI, bool *CPSR) {
 bool ARMFastISel::isARMNEONPred(const MachineInstr *MI) {
   const MCInstrDesc &MCID = MI->getDesc();
 
-  // If we're a thumb2 or not NEON function we were handled via isPredicable.
+  // If we're a thumb2 or not NEON function we'll be handled via isPredicable.
   if ((MCID.TSFlags & ARMII::DomainMask) != ARMII::DomainNEON ||
        AFI->isThumb2Function())
-    return false;
+    return MI->isPredicable();
 
   for (unsigned i = 0, e = MCID.getNumOperands(); i != e; ++i)
     if (MCID.OpInfo[i].isPredicate())
@@ -278,7 +278,7 @@ ARMFastISel::AddOptionalDefs(const MachineInstrBuilder &MIB) {
   // Do we use a predicate? or...
   // Are we NEON in ARM mode and have a predicate operand? If so, I know
   // we're not predicable but add it anyways.
-  if (TII.isPredicable(MI) || isARMNEONPred(MI))
+  if (isARMNEONPred(MI))
     AddDefaultPred(MIB);
 
   // Do we optionally set a predicate?  Preds is size > 0 iff the predicate
diff --git a/lib/Target/ARM/ARMTargetMachine.cpp b/lib/Target/ARM/ARMTargetMachine.cpp
index 1ba78e4a98..c78db54d8b 100644
--- a/lib/Target/ARM/ARMTargetMachine.cpp
+++ b/lib/Target/ARM/ARMTargetMachine.cpp
@@ -196,8 +196,13 @@ bool ARMPassConfig::addPreSched2() {
   addPass(createARMExpandPseudoPass());
 
   if (getOptLevel() != CodeGenOpt::None) {
-    if (!getARMSubtarget().isThumb1Only())
+    if (!getARMSubtarget().isThumb1Only()) {
+      // in v8, IfConversion depends on Thumb instruction widths
+      if (getARMSubtarget().hasV8Ops() &&
+          !getARMSubtarget().prefers32BitThumb())
+        addPass(createThumb2SizeReductionPass());
       addPass(&IfConverterID);
+    }
   }
   if (getARMSubtarget().isThumb2())
     addPass(createThumb2ITBlockPass());
diff --git a/lib/Target/ARM/Thumb2ITBlockPass.cpp b/lib/Target/ARM/Thumb2ITBlockPass.cpp
index d8596d7993..8f1ae2eaf8 100644
--- a/lib/Target/ARM/Thumb2ITBlockPass.cpp
+++ b/lib/Target/ARM/Thumb2ITBlockPass.cpp
@@ -28,6 +28,7 @@ namespace {
     static char ID;
     Thumb2ITBlockPass() : MachineFunctionPass(ID) {}
 
+    bool hasV8Ops;
     const Thumb2InstrInfo *TII;
     const TargetRegisterInfo *TRI;
     ARMFunctionInfo *AFI;
@@ -192,37 +193,41 @@ bool Thumb2ITBlockPass::InsertITInstructions(MachineBasicBlock &MBB) {
     // Form IT block.
     ARMCC::CondCodes OCC = ARMCC::getOppositeCondition(CC);
     unsigned Mask = 0, Pos = 3;
-    // Branches, including tricky ones like LDM_RET, need to end an IT
-    // block so check the instruction we just put in the block.
-    for (; MBBI != E && Pos &&
-           (!MI->isBranch() && !MI->isReturn()) ; ++MBBI) {
-      if (MBBI->isDebugValue())
-        continue;
-
-      MachineInstr *NMI = &*MBBI;
-      MI = NMI;
-
-      unsigned NPredReg = 0;
-      ARMCC::CondCodes NCC = getITInstrPredicate(NMI, NPredReg);
-      if (NCC == CC || NCC == OCC) {
-        Mask |= (NCC & 1) << Pos;
-        // Add implicit use of ITSTATE.
-        NMI->addOperand(MachineOperand::CreateReg(ARM::ITSTATE, false/*ifDef*/,
-                                               true/*isImp*/, false/*isKill*/));
-        LastITMI = NMI;
-      } else {
-        if (NCC == ARMCC::AL &&
-            MoveCopyOutOfITBlock(NMI, CC, OCC, Defs, Uses)) {
-          --MBBI;
-          MBB.remove(NMI);
-          MBB.insert(InsertPos, NMI);
-          ++NumMovedInsts;
+
+    // v8 IT blocks are limited to one conditional op: skip the loop
+    if (!hasV8Ops) {
+      // Branches, including tricky ones like LDM_RET, need to end an IT
+      // block so check the instruction we just put in the block.
+      for (; MBBI != E && Pos &&
+             (!MI->isBranch() && !MI->isReturn()) ; ++MBBI) {
+        if (MBBI->isDebugValue())
           continue;
+
+        MachineInstr *NMI = &*MBBI;
+        MI = NMI;
+
+        unsigned NPredReg = 0;
+        ARMCC::CondCodes NCC = getITInstrPredicate(NMI, NPredReg);
+        if (NCC == CC || NCC == OCC) {
+          Mask |= (NCC & 1) << Pos;
+          // Add implicit use of ITSTATE.
+          NMI->addOperand(MachineOperand::CreateReg(ARM::ITSTATE, false/*ifDef*/,
+                                                 true/*isImp*/, false/*isKill*/));
+          LastITMI = NMI;
+        } else {
+          if (NCC == ARMCC::AL &&
+              MoveCopyOutOfITBlock(NMI, CC, OCC, Defs, Uses)) {
+            --MBBI;
+            MBB.remove(NMI);
+            MBB.insert(InsertPos, NMI);
+            ++NumMovedInsts;
+            continue;
+          }
+          break;
         }
-        break;
+        TrackDefUses(NMI, Defs, Uses, TRI);
+        --Pos;
       }
-      TrackDefUses(NMI, Defs, Uses, TRI);
-      --Pos;
     }
 
     // Finalize IT mask.
@@ -250,6 +255,7 @@ bool Thumb2ITBlockPass::runOnMachineFunction(MachineFunction &Fn) {
   AFI = Fn.getInfo<ARMFunctionInfo>();
   TII = static_cast<const Thumb2InstrInfo*>(TM.getInstrInfo());
   TRI = TM.getRegisterInfo();
+  hasV8Ops = TM.getSubtarget<ARMSubtarget>().hasV8Ops();
 
   if (!AFI->isThumbFunction())
     return false;