[ARM] Use just ARM::t2B in ARMBlockPlacementPass

The ARMConstantIsland pass will convert any t2B to tB if they are within
range after it has added or moved any constant pools. They don't need to
be deliberately converted beforehand, and it doesn't deal with needing
to convert tB to t2B very well.

Author: davemgreen

llvm/lib/Target/ARM/ARMBlockPlacement.cpp

@@ -145,8 +145,7 @@ bool ARMBlockPlacement::runOnMachineFunction(MachineFunction &MF) {
              It++) {
           MachineBasicBlock *MBB = &*It;
           for (auto &Terminator : MBB->terminators()) {
-            if (Terminator.getOpcode() != ARM::t2LoopEnd &&
-                Terminator.getOpcode() != ARM::t2LoopEndDec)
+            if (Terminator.getOpcode() != ARM::t2LoopEndDec)
               continue;
             MachineBasicBlock *LETarget = Terminator.getOperand(2).getMBB();
             // The LE will become forwards branching if it branches to LoopExit
@@ -204,10 +203,8 @@ void ARMBlockPlacement::moveBasicBlock(MachineBasicBlock *BB,
     if (!Terminator.isUnconditionalBranch()) {
       // The BB doesn't have an unconditional branch so it relied on
       // fall-through. Fix by adding an unconditional branch to the moved BB.
-      unsigned BrOpc =
-          BBUtils->isBBInRange(&Terminator, To, 254) ? ARM::tB : ARM::t2B;
       MachineInstrBuilder MIB =
-          BuildMI(From, Terminator.getDebugLoc(), TII->get(BrOpc));
+          BuildMI(From, Terminator.getDebugLoc(), TII->get(ARM::t2B));
       MIB.addMBB(To);
       MIB.addImm(ARMCC::CondCodes::AL);
       MIB.addReg(ARM::NoRegister);

llvm/test/CodeGen/Thumb2/block-placement.mir

@@ -48,7 +48,7 @@ body:             |
   ; CHECK: bb.2:
   ; CHECK:   successors: %bb.3(0x80000000)
   ; CHECK:   t2WhileLoopStart killed renamable $r0, %bb.1, implicit-def dead $cpsr
-  ; CHECK:   tB %bb.3, 14 /* CC::al */, $noreg
+  ; CHECK:   t2B %bb.3, 14 /* CC::al */, $noreg
   ; CHECK: bb.1:
   ; CHECK:   frame-destroy tPOP_RET 14 /* CC::al */, $noreg, def $r7, def $pc
   ; CHECK: bb.3:
@@ -145,7 +145,7 @@ body:             |
   ; CHECK:   $lr = tMOVr $r0, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r0 = t2ADDrs killed renamable $r2, killed $r0, 18, 14 /* CC::al */, $noreg, $noreg
   ; CHECK:   t2WhileLoopStart killed renamable $lr, %bb.1, implicit-def dead $cpsr
-  ; CHECK:   tB %bb.3, 14 /* CC::al */, $noreg
+  ; CHECK:   t2B %bb.3, 14 /* CC::al */, $noreg
   ; CHECK: bb.1:
   ; CHECK:   successors: %bb.4(0x80000000)
   ; CHECK:   tCMPi8 renamable $r1, 1, 14 /* CC::al */, $noreg, implicit-def $cpsr