From 6f4f46cf112567e273504b41b47301f922347577 Mon Sep 17 00:00:00 2001
From: Adam Nemet <anemet@apple.com>
Date: Tue, 25 Mar 2014 17:47:06 +0000
Subject: [PATCH] [X86] Generate VPSHUFB for in-place v16i16 shuffles

This used to resort to splitting the 256-bit operation into two 128-bit
shuffles and then recombining the results.

Fixes <rdar://problem/16167303>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204735 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 25 +++++++++++++++++++++++++
 test/CodeGen/X86/vec_shuffle-40.ll | 22 ++++++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 test/CodeGen/X86/vec_shuffle-40.ll

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 14d7be31306..ec923ba7aa2 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -6576,6 +6576,25 @@ LowerVECTOR_SHUFFLEv8i16(SDValue Op, const X86Subtarget *Subtarget,
   return NewV;
 }
 
+/// \brief v16i16 shuffles
+///
+/// FIXME: We only support generation of a single pshufb currently.  We can
+/// generalize the other applicable cases from LowerVECTOR_SHUFFLEv8i16 as
+/// well (e.g 2 x pshufb + 1 x por).
+static SDValue
+LowerVECTOR_SHUFFLEv16i16(SDValue Op, SelectionDAG &DAG) {
+  ShuffleVectorSDNode *SVOp = cast<ShuffleVectorSDNode>(Op);
+  SDValue V1 = SVOp->getOperand(0);
+  SDValue V2 = SVOp->getOperand(1);
+  SDLoc dl(SVOp);
+
+  if (V2.getOpcode() != ISD::UNDEF)
+    return SDValue();
+
+  SmallVector<int, 16> MaskVals(SVOp->getMask().begin(), SVOp->getMask().end());
+  return getPSHUFB(MaskVals, V1, dl, DAG);
+}
+
 // v16i8 shuffles - Prefer shuffles in the following order:
 // 1. [ssse3] 1 x pshufb
 // 2. [ssse3] 2 x pshufb + 1 x por
@@ -7635,6 +7654,12 @@ X86TargetLowering::LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) const {
       return NewOp;
   }
 
+  if (VT == MVT::v16i16 && Subtarget->hasInt256()) {
+    SDValue NewOp = LowerVECTOR_SHUFFLEv16i16(Op, DAG);
+    if (NewOp.getNode())
+      return NewOp;
+  }
+
   if (VT == MVT::v16i8) {
     SDValue NewOp = LowerVECTOR_SHUFFLEv16i8(SVOp, Subtarget, DAG);
     if (NewOp.getNode())
diff --git a/test/CodeGen/X86/vec_shuffle-40.ll b/test/CodeGen/X86/vec_shuffle-40.ll
new file mode 100644
index 00000000000..75b45e3df11
--- /dev/null
+++ b/test/CodeGen/X86/vec_shuffle-40.ll
@@ -0,0 +1,22 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin -mcpu=core-avx2 | FileCheck %s
+
+define void @shuffle_v16i16(<16 x i16>* %a) {
+; CHECK-LABEL: shuffle_v16i16:
+; CHECK: vpshufb {{.*}}%ymm
+; CHECK-NOT: vpshufb {{.*}}%xmm
+entry:
+  %0 = load <16 x i16>* %a, align 32
+  %shuffle = shufflevector <16 x i16> %0, <16 x i16> undef, <16 x i32> <i32 1, i32 1, i32 3, i32 3, i32 5, i32 5, i32 7, i32 7, i32 9, i32 9, i32 11, i32 11, i32 13, i32 13, i32 15, i32 15>
+  store <16 x i16> %shuffle, <16 x i16>* %a, align 32
+  ret void
+}
+
+define void @shuffle_v16i16_lanecrossing(<16 x i16>* %a) {
+; CHECK-LABEL: shuffle_v16i16_lanecrossing:
+; CHECK-NOT: vpshufb {{.*}}%ymm
+entry:
+  %0 = load <16 x i16>* %a, align 32
+  %shuffle = shufflevector <16 x i16> %0, <16 x i16> undef, <16 x i32> <i32 1, i32 1, i32 3, i32 3, i32 5, i32 13, i32 7, i32 7, i32 9, i32 9, i32 11, i32 11, i32 13, i32 13, i32 15, i32 15>
+  store <16 x i16> %shuffle, <16 x i16>* %a, align 32
+  ret void
+}