[WebAssembly] vNxM.load_splat instructions

Summary:
Adds the new load_splat instructions as specified at
https://github.com/WebAssembly/simd/blob/master/proposals/simd/SIMD.md#load-and-splat.

DAGISel does not allow matching multiple copies of the same load in a
single pattern, so we use a new node in WebAssemblyISD to wrap loads
that should be splatted.

Depends on D67783.

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67784

llvm-svn: 372655

1 files changed, 10 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index 49a9fb0c619..8528d930d21 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -1358,7 +1358,16 @@ SDValue WebAssemblyTargetLowering::LowerBUILD_VECTOR(SDValue Op,
     }
   }
   // Use a splat for the initial vector
-  SDValue Result = DAG.getSplatBuildVector(VecT, DL, SplatValue);
+  SDValue Result;
+  // Possibly a load_splat
+  LoadSDNode *SplattedLoad;
+  if (Subtarget->hasUnimplementedSIMD128() &&
+      (SplattedLoad = dyn_cast<LoadSDNode>(SplatValue)) &&
+      SplattedLoad->getMemoryVT() == VecT.getVectorElementType()) {
+    Result = DAG.getNode(WebAssemblyISD::LOAD_SPLAT, DL, VecT, SplatValue);
+  } else {
+    Result = DAG.getSplatBuildVector(VecT, DL, SplatValue);
+  }
   // Add replace_lane instructions for other values
   for (size_t I = 0; I < Lanes; ++I) {
     const SDValue &Lane = Op->getOperand(I);