Make tBX_RET and tBX_RET_vararg predicable.

The normal tBX instruction is predicable, so there's no reason the
pseudos for using it as a return shouldn't be. Gives us some nice code-gen
improvements as can be seen by the test changes. In particular, several
tests now have to disable if-conversion because it works too well and defeats
the test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134746 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 10 insertions, 7 deletions

diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp
index 309caee42b..f45ebdc535 100644
--- a/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -1538,7 +1538,10 @@ bool ARMConstantIslands::UndoLRSpillRestore() {
     if (MI->getOpcode() == ARM::tPOP_RET &&
         MI->getOperand(2).getReg() == ARM::PC &&
         MI->getNumExplicitOperands() == 3) {
-      BuildMI(MI->getParent(), MI->getDebugLoc(), TII->get(ARM::tBX_RET));
+      // Create the new insn and copy the predicate from the old.
+      BuildMI(MI->getParent(), MI->getDebugLoc(), TII->get(ARM::tBX_RET))
+        .addOperand(MI->getOperand(0))
+        .addOperand(MI->getOperand(1));
       MI->eraseFromParent();
       MadeChange = true;
     }
diff --git a/lib/Target/ARM/ARMInstrThumb.td b/lib/Target/ARM/ARMInstrThumb.td
index 9a96dc7fda..bba0ab6450 100644
--- a/lib/Target/ARM/ARMInstrThumb.td
+++ b/lib/Target/ARM/ARMInstrThumb.td
@@ -385,13 +385,13 @@ let isBranch = 1, isTerminator = 1, isBarrier = 1, isIndirectBranch = 1 in {
 }
 
 let isReturn = 1, isTerminator = 1, isBarrier = 1 in {
-  def tBX_RET : tPseudoExpand<(outs), (ins), Size2Bytes, IIC_Br,
-                   [(ARMretflag)], (tBX LR, (ops 14, zero_reg))>;
+  def tBX_RET : tPseudoExpand<(outs), (ins pred:$p), Size2Bytes, IIC_Br,
+                   [(ARMretflag)], (tBX LR, pred:$p)>;
 
   // Alternative return instruction used by vararg functions.
-  def tBX_RET_vararg : tPseudoExpand<(outs), (ins tGPR:$Rm),
+  def tBX_RET_vararg : tPseudoExpand<(outs), (ins tGPR:$Rm, pred:$p),
                    Size2Bytes, IIC_Br, [],
-                   (tBX GPR:$Rm, (ops 14, zero_reg))>;
+                   (tBX GPR:$Rm, pred:$p)>;
 }
 
 // All calls clobber the non-callee saved registers. SP is marked as a use to
diff --git a/lib/Target/ARM/Thumb1FrameLowering.cpp b/lib/Target/ARM/Thumb1FrameLowering.cpp
index 48211d852f..c258870e48 100644
--- a/lib/Target/ARM/Thumb1FrameLowering.cpp
+++ b/lib/Target/ARM/Thumb1FrameLowering.cpp
@@ -273,8 +273,8 @@ void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF,
 
     emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, VARegSaveSize);
 
-    BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX_RET_vararg))
-      .addReg(ARM::R3, RegState::Kill);
+    AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX_RET_vararg))
+      .addReg(ARM::R3, RegState::Kill));
     // erase the old tBX_RET instruction
     MBB.erase(MBBI);
   }