ARM: implement allowTruncateForTailCall

Now that it's in place, it seems silly not to let ARM make use of the extra
tail call opportunities.

llvm-svn: 187795

2 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 61c5bd14c95..caec11e108f 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -9993,6 +9993,21 @@ bool ARMTargetLowering::isZExtFree(SDValue Val, EVT VT2) const {
   return false;
 }
 
+bool ARMTargetLowering::allowTruncateForTailCall(Type *Ty1, Type *Ty2) const {
+  if (!Ty1->isIntegerTy() || !Ty2->isIntegerTy())
+    return false;
+
+  if (!isTypeLegal(EVT::getEVT(Ty1)))
+    return false;
+
+  assert(Ty1->getPrimitiveSizeInBits() <= 64 && "i128 is probably not a noop");
+
+  // Assuming the caller doesn't have a zeroext or signext return parameter,
+  // truncation all the way down to i1 is valid.
+  return true;
+}
+
+
 static bool isLegalT1AddressImmediate(int64_t V, EVT VT) {
   if (V < 0)
     return false;
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index beba5ce7715..44c769f8221 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -298,6 +298,9 @@ namespace llvm {
     using TargetLowering::isZExtFree;
     virtual bool isZExtFree(SDValue Val, EVT VT2) const;
 
+    virtual bool allowTruncateForTailCall(Type *Ty1, Type *Ty2) const;
+
+
     /// isLegalAddressingMode - Return true if the addressing mode represented
     /// by AM is legal for this target, for a load/store of the specified type.
     virtual bool isLegalAddressingMode(const AddrMode &AM, Type *Ty)const;