[PATCH] D159278: [AArch64] Improve vector multiply by constant

[Priyanshi Agarwal via Phabricator via llvm-commits]

ipriyanshi1708 created this revision.
Herald added subscribers: sunshaoce, hiraditya, kristof.beyls.
Herald added a project: All.
ipriyanshi1708 requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Issue: https://github.com/llvm/llvm-project/issues/54651


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159278

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.h


Index: llvm/lib/Target/AArch64/AArch64ISelLowering.h
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -1201,7 +1201,8 @@
                                          unsigned Depth) const override;
 
   bool isTargetCanonicalConstantNode(SDValue Op) const override;
-
+  bool decomposeMulByConstant(LLVMContext &Context, EVT VT,
+                            SDValue C) const override;
   // With the exception of data-predicate transitions, no instructions are
   // required to cast between legal scalable vector types. However:
   //  1. Packed and unpacked types have different bit lengths, meaning BITCAST
Index: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -24327,6 +24327,19 @@
   return Ty1 == Ty2 && (Ty1 == LLT::scalar(32) || Ty1 == LLT::scalar(64));
 }
 
+bool AArch64TargetLowering::decomposeMulByConstant(LLVMContext &Context, EVT VT,
+                                               SDValue C) const {
+  if (VT == MVT::v2i64)
+    return true;
+
+  APInt MulC;
+  if (!ISD::isConstantSplatVector(C.getNode(), MulC))
+    return false;
+
+  return (MulC + 1).isPowerOf2() || (MulC - 1).isPowerOf2() ||
+         (1 - MulC).isPowerOf2() || (-(MulC + 1)).isPowerOf2();
+}
+
 bool AArch64TargetLowering::isComplexDeinterleavingSupported() const {
   return Subtarget->hasComplxNum();
 }


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