Optimize sext <4 x i8> and <4 x i16> to <4 x i64>.

Patch by Ahmad, Muhammad T <muhammad.t.ahmad@intel.com>

llvm-svn: 177421

2 files changed, 19 insertions, 4 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 10cf13f2aa9..5c2f6517eeb 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -11827,8 +11827,23 @@ SDValue X86TargetLowering::LowerSIGN_EXTEND_INREG(SDValue Op,
       // fall through
     case MVT::v4i32:
     case MVT::v8i16: {
-      SDValue Tmp1 = getTargetVShiftNode(X86ISD::VSHLI, dl, VT,
-                                         Op.getOperand(0), ShAmt, DAG);
+      // (sext (vzext x)) -> (vsext x)
+      SDValue Op0 = Op.getOperand(0);
+      SDValue Op00 = Op0.getOperand(0);
+      SDValue Tmp1;
+      // Hopefully, this VECTOR_SHUFFLE is just a VZEXT.
+      if (Op0.getOpcode() == ISD::BITCAST &&
+          Op00.getOpcode() == ISD::VECTOR_SHUFFLE)
+        Tmp1 = LowerVectorIntExtend(Op00, DAG);
+      if (Tmp1.getNode()) {
+        SDValue Tmp1Op0 = Tmp1.getOperand(0);
+        assert(Tmp1Op0.getOpcode() == X86ISD::VZEXT &&
+               "This optimization is invalid without a VZEXT.");
+        return DAG.getNode(X86ISD::VSEXT, dl, VT, Tmp1Op0.getOperand(0));
+      }
+
+      // If the above didn't work, then just use Shift-Left + Shift-Right.
+      Tmp1 = getTargetVShiftNode(X86ISD::VSHLI, dl, VT, Op0, ShAmt, DAG);
       return getTargetVShiftNode(X86ISD::VSRAI, dl, VT, Tmp1, ShAmt, DAG);
     }
   }
diff --git a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
index be2a997b8e0..777ef508ec3 100644
--- a/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
+++ b/llvm/lib/Target/X86/X86TargetTransformInfo.cpp
@@ -257,8 +257,8 @@ unsigned X86TTI::getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src) const {
     { ISD::ZERO_EXTEND, MVT::v8i32, MVT::v8i1,  6 },
     { ISD::SIGN_EXTEND, MVT::v8i32, MVT::v8i1,  9 },
     { ISD::SIGN_EXTEND, MVT::v4i64, MVT::v4i1,  8 },
-    { ISD::SIGN_EXTEND, MVT::v4i64, MVT::v4i8,  8 },
-    { ISD::SIGN_EXTEND, MVT::v4i64, MVT::v4i16, 8 },
+    { ISD::SIGN_EXTEND, MVT::v4i64, MVT::v4i8,  6 },
+    { ISD::SIGN_EXTEND, MVT::v4i64, MVT::v4i16, 6 },
     { ISD::TRUNCATE,    MVT::v8i32, MVT::v8i64, 3 },
   };