[AArch64] Implement the isZExtFree APIs.

llvm-svn: 205926

2 files changed, 40 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 7accadc6a0f..589734d80fe 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -5389,3 +5389,39 @@ bool AArch64TargetLowering::isTruncateFree(EVT VT1, EVT VT2) const {
     return false;
   return true;
 }
+
+// All 32-bit GPR operations implicitly zero the high-half of the corresponding
+// 64-bit GPR.
+bool AArch64TargetLowering::isZExtFree(Type *Ty1, Type *Ty2) const {
+  if (!Ty1->isIntegerTy() || !Ty2->isIntegerTy())
+    return false;
+  unsigned NumBits1 = Ty1->getPrimitiveSizeInBits();
+  unsigned NumBits2 = Ty2->getPrimitiveSizeInBits();
+  if (NumBits1 == 32 && NumBits2 == 64)
+    return true;
+  return false;
+}
+
+bool AArch64TargetLowering::isZExtFree(EVT VT1, EVT VT2) const {
+  if (!VT1.isInteger() || !VT2.isInteger())
+    return false;
+  unsigned NumBits1 = VT1.getSizeInBits();
+  unsigned NumBits2 = VT2.getSizeInBits();
+  if (NumBits1 == 32 && NumBits2 == 64)
+    return true;
+  return false;
+}
+
+bool AArch64TargetLowering::isZExtFree(SDValue Val, EVT VT2) const {
+  EVT VT1 = Val.getValueType();
+  if (isZExtFree(VT1, VT2)) {
+    return true;
+  }
+
+  if (Val.getOpcode() != ISD::LOAD)
+    return false;
+
+  // 8-, 16-, and 32-bit integer loads all implicitly zero-extend.
+  return (VT1.isSimple() && VT1.isInteger() && VT2.isSimple() &&
+          VT2.isInteger() && VT1.getSizeInBits() <= 32);
+}
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.h b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
index 6a4b0c791fe..5932e1d1fe5 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -281,6 +281,10 @@ public:
   bool isTruncateFree(Type *Ty1, Type *Ty2) const override;
   bool isTruncateFree(EVT VT1, EVT VT2) const override;
 
+  bool isZExtFree(Type *Ty1, Type *Ty2) const override;
+  bool isZExtFree(EVT VT1, EVT VT2) const override;
+  bool isZExtFree(SDValue Val, EVT VT2) const override;
+
   SDValue getSelectableIntSetCC(SDValue LHS, SDValue RHS, ISD::CondCode CC,
                          SDValue &A64cc, SelectionDAG &DAG, SDLoc &dl) const;