[PATCH] D14207: [AArch64] Handle extract_subvector(..., 0) in ISel.

[Charlie Turner via llvm-commits]

chatur01 created this revision.
chatur01 added a reviewer: t.p.northover.
chatur01 added a subscriber: llvm-commits.
chatur01 set the repository for this revision to rL LLVM.
Herald added subscribers: rengolin, aemerson.

Lowering this pattern early to an `EXTRACT_SUBREG` was making it impossible to match larger patterns in tblgen that use `extract_subvector(..., 0)` as part of the their input pattern.

It seems like there will exist somewhere a better way of specifying this pattern over all relevant register value types, but I didn't manage to find it.

Repository:
  rL LLVM

http://reviews.llvm.org/D14207

Files:
  lib/Target/AArch64/AArch64ISelLowering.cpp
  lib/Target/AArch64/AArch64InstrInfo.td

Index: lib/Target/AArch64/AArch64InstrInfo.td
===================================================================
--- lib/Target/AArch64/AArch64InstrInfo.td
+++ lib/Target/AArch64/AArch64InstrInfo.td
@@ -5788,6 +5788,21 @@
                              (v16i8 (REV16v16i8 FPR128:$src))>;
 }
 
+def : Pat<(v4i16 (extract_subvector V128:$Rn, (i64 0))),
+           (EXTRACT_SUBREG V128:$Rn, dsub)>;
+def : Pat<(v8i8 (extract_subvector V128:$Rn, (i64 0))),
+           (EXTRACT_SUBREG V128:$Rn, dsub)>;
+def : Pat<(v2f32 (extract_subvector V128:$Rn, (i64 0))),
+           (EXTRACT_SUBREG V128:$Rn, dsub)>;
+def : Pat<(v4f16 (extract_subvector V128:$Rn, (i64 0))),
+           (EXTRACT_SUBREG V128:$Rn, dsub)>;
+def : Pat<(v2i32 (extract_subvector V128:$Rn, (i64 0))),
+           (EXTRACT_SUBREG V128:$Rn, dsub)>;
+def : Pat<(v1i64 (extract_subvector V128:$Rn, (i64 0))),
+           (EXTRACT_SUBREG V128:$Rn, dsub)>;
+def : Pat<(v1f64 (extract_subvector V128:$Rn, (i64 0))),
+           (EXTRACT_SUBREG V128:$Rn, dsub)>;
+
 def : Pat<(v8i8 (extract_subvector (v16i8 FPR128:$Rn), (i64 1))),
           (EXTRACT_SUBREG (DUPv2i64lane FPR128:$Rn, 1), dsub)>;
 def : Pat<(v4i16 (extract_subvector (v8i16 FPR128:$Rn), (i64 1))),
Index: lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- lib/Target/AArch64/AArch64ISelLowering.cpp
+++ lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -6400,24 +6400,11 @@
   unsigned Val = Cst->getZExtValue();
 
   unsigned Size = Op.getValueType().getSizeInBits();
-  if (Val == 0) {
-    switch (Size) {
-    case 8:
-      return DAG.getTargetExtractSubreg(AArch64::bsub, dl, Op.getValueType(),
-                                        Op.getOperand(0));
-    case 16:
-      return DAG.getTargetExtractSubreg(AArch64::hsub, dl, Op.getValueType(),
-                                        Op.getOperand(0));
-    case 32:
-      return DAG.getTargetExtractSubreg(AArch64::ssub, dl, Op.getValueType(),
-                                        Op.getOperand(0));
-    case 64:
-      return DAG.getTargetExtractSubreg(AArch64::dsub, dl, Op.getValueType(),
-                                        Op.getOperand(0));
-    default:
-      llvm_unreachable("Unexpected vector type in extract_subvector!");
-    }
-  }
+
+  // This will get lowered to an appropriate EXTRACT_SUBREG in ISel.
+  if (Val == 0)
+    return Op;
+
   // If this is extracting the upper 64-bits of a 128-bit vector, we match
   // that directly.
   if (Size == 64 && Val * VT.getVectorElementType().getSizeInBits() == 64)


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