Add a thumb2 pass to insert IT blocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75218 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/Thumb2ITBlockPass.cpp

@@ -0,0 +1,108 @@
+//===-- Thumb2ITBlockPass.cpp - Insert Thumb IT blocks -----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "thumb2-it"
+#include "ARM.h"
+#include "ARMInstrInfo.h"
+#include "ARMMachineFunctionInfo.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/Statistic.h"
+using namespace llvm;
+
+STATISTIC(NumITs,     "Number of IT blocks inserted");
+
+namespace {
+  struct VISIBILITY_HIDDEN Thumb2ITBlockPass : public MachineFunctionPass {
+    static char ID;
+    Thumb2ITBlockPass() : MachineFunctionPass(&ID) {}
+
+    const ARMBaseInstrInfo *TII;
+    ARMFunctionInfo *AFI;
+
+    virtual bool runOnMachineFunction(MachineFunction &Fn);
+
+    virtual const char *getPassName() const {
+      return "Thumb IT blocks insertion pass";
+    }
+
+  private:
+    bool InsertITBlocks(MachineBasicBlock &MBB);
+  };
+  char Thumb2ITBlockPass::ID = 0;
+}
+
+bool Thumb2ITBlockPass::InsertITBlocks(MachineBasicBlock &MBB) {
+  bool Modified = false;
+
+  MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
+  while (MBBI != E) {
+    MachineInstr *MI = &*MBBI;
+    ARMCC::CondCodes CC = TII->getPredicate(MI);
+    if (CC == ARMCC::AL) {
+      ++MBBI;
+      continue;
+    }
+
+    // Insert an IT instruction.
+    DebugLoc dl = MI->getDebugLoc();
+    MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII->get(ARM::t2IT))
+      .addImm(CC);
+    ++MBBI;
+
+    // Finalize IT mask. If the following instruction is not predicated or it's
+    // predicated on a condition that's not the same or the opposite of CC, then
+    // the mask is 0x8.
+    ARMCC::CondCodes OCC = ARMCC::getOppositeCondition(CC);
+    unsigned Mask = 0x8;
+    while (MBBI != E || (Mask & 1)) {
+      ARMCC::CondCodes NCC = TII->getPredicate(&*MBBI);
+      if (NCC == CC) {
+        Mask >>= 1;
+        Mask |= 0x8;
+      } else if (NCC == OCC) {
+        Mask >>= 1;
+      } else {
+        break;
+      }
+      ++MBBI;
+    }
+    MIB.addImm(Mask);
+    Modified = true;
+    ++NumITs;
+  }
+
+  return Modified;
+}
+
+bool Thumb2ITBlockPass::runOnMachineFunction(MachineFunction &Fn) {
+  const TargetMachine &TM = Fn.getTarget();
+  AFI = Fn.getInfo<ARMFunctionInfo>();
+  TII = static_cast<const ARMBaseInstrInfo*>(TM.getInstrInfo());
+
+  if (!AFI->isThumbFunction())
+    return false;
+
+  bool Modified = false;
+  for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
+       ++MFI) {
+    MachineBasicBlock &MBB = *MFI;
+    Modified |= InsertITBlocks(MBB);
+  }
+
+  return Modified;
+}
+
+/// createThumb2ITBlockPass - returns and instance of the Thumb IT blocks
+/// insertion pass.
+FunctionPass *llvm::createThumb2ITBlockPass() {
+  return new Thumb2ITBlockPass();
+}