[aarch64] move custom isel of extract_vector_elt to td file - NFC

In preparation for def-pat selection of dot product instructions,
this patch moves the custom instruction selection of extract_vector_elt
to the td file. Without this change it is impossible to catch a pattern that
starts with an extract_vector_elt: the custom cpp code is executed first
ahead of the patterns in the td files that are only executed at the end of
the switch statement in SelectCode(Node).

With this patch applied, it becomes possible to select a different pattern
that starts with extract_vector_elt by selecting a higher complexity than
this pattern.

The patch has been tested on aarch64-linux with make check-all.

Differential Revision: https://reviews.llvm.org/D67497

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371887 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp b/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
index cd7e927ac80cae950ad4126602e71cb4bce54b40..dba34a96304b4d6a90b06d1811528fbb031fa98c 100644 (file)
--- a/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
+++ b/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
@@ -2913,49 +2913,6 @@ void AArch64DAGToDAGISel::Select(SDNode *Node) {
       return;
     break;
 
-  case ISD::EXTRACT_VECTOR_ELT: {
-    // Extracting lane zero is a special case where we can just use a plain
-    // EXTRACT_SUBREG instruction, which will become FMOV. This is easier for
-    // the rest of the compiler, especially the register allocator and copyi
-    // propagation, to reason about, so is preferred when it's possible to
-    // use it.
-    ConstantSDNode *LaneNode = cast<ConstantSDNode>(Node->getOperand(1));
-    // Bail and use the default Select() for non-zero lanes.
-    if (LaneNode->getZExtValue() != 0)
-      break;
-    // If the element type is not the same as the result type, likewise
-    // bail and use the default Select(), as there's more to do than just
-    // a cross-class COPY. This catches extracts of i8 and i16 elements
-    // since they will need an explicit zext.
-    if (VT != Node->getOperand(0).getValueType().getVectorElementType())
-      break;
-    unsigned SubReg;
-    switch (Node->getOperand(0)
-                .getValueType()
-                .getVectorElementType()
-                .getSizeInBits()) {
-    default:
-      llvm_unreachable("Unexpected vector element type!");
-    case 64:
-      SubReg = AArch64::dsub;
-      break;
-    case 32:
-      SubReg = AArch64::ssub;
-      break;
-    case 16:
-      SubReg = AArch64::hsub;
-      break;
-    case 8:
-      llvm_unreachable("unexpected zext-requiring extract element!");
-    }
-    SDValue Extract = CurDAG->getTargetExtractSubreg(SubReg, SDLoc(Node), VT,
-                                                     Node->getOperand(0));
-    LLVM_DEBUG(dbgs() << "ISEL: Custom selection!\n=> ");
-    LLVM_DEBUG(Extract->dumpr(CurDAG));
-    LLVM_DEBUG(dbgs() << "\n");
-    ReplaceNode(Node, Extract.getNode());
-    return;
-  }
   case ISD::Constant: {
     // Materialize zero constants as copies from WZR/XZR.  This allows
     // the coalescer to propagate these into other instructions.

diff --git a/lib/Target/AArch64/AArch64InstrInfo.td b/lib/Target/AArch64/AArch64InstrInfo.td
index 7123ba043c325e5b7a33f619f7faab25f517655c..541b7ce80e30c673c54862dfe886c32c9e3d7b37 100644 (file)
--- a/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/lib/Target/AArch64/AArch64InstrInfo.td
@@ -6973,5 +6973,15 @@ def : Pat<(AArch64tcret texternalsym:$dst, (i32 timm:$FPDiff)),
 def MOVMCSym : Pseudo<(outs GPR64:$dst), (ins i64imm:$sym), []>, Sched<[]>;
 def : Pat<(i64 (AArch64LocalRecover mcsym:$sym)), (MOVMCSym mcsym:$sym)>;
 
+// Extracting lane zero is a special case where we can just use a plain
+// EXTRACT_SUBREG instruction, which will become FMOV. This is easier for the
+// rest of the compiler, especially the register allocator and copy propagation,
+// to reason about, so is preferred when it's possible to use it.
+let AddedComplexity = 10 in {
+  def : Pat<(i64 (extractelt (v2i64 V128:$V), (i64 0))), (EXTRACT_SUBREG V128:$V, dsub)>;
+  def : Pat<(i32 (extractelt (v4i32 V128:$V), (i64 0))), (EXTRACT_SUBREG V128:$V, ssub)>;
+  def : Pat<(i32 (extractelt (v2i32 V64:$V), (i64 0))), (EXTRACT_SUBREG V64:$V, ssub)>;
+}
+
 include "AArch64InstrAtomics.td"
 include "AArch64SVEInstrInfo.td"