[PATCH] D80485: [DAGCombiner][PowerPC][AArch64] Remove isMulhCheaperThanMulShift TLI hook. Use isOperationLegal directly instead.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: amyk, RKSimon, nemanjai, spatel, efriedma.
Herald added subscribers: ecnelises, danielkiss, shchenz, kbarton, hiraditya, kristof.beyls.
Herald added a project: LLVM.

MULH is often expanded on targets. So we can probably get by with
just using isOperationLegal instead of having a TLI hook.

I had to make i32 MULH Expand on AArch64 to prevent an accidental
reliance on DAGCombine promoting to i64 multiply.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80485

Files:
  llvm/include/llvm/CodeGen/TargetLowering.h
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.cpp
  llvm/lib/Target/PowerPC/PPCISelLowering.h


Index: llvm/lib/Target/PowerPC/PPCISelLowering.h
===================================================================
--- llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -950,11 +950,6 @@
     Register
     getExceptionSelectorRegister(const Constant *PersonalityFn) const override;
 
-    /// isMulhCheaperThanMulShift - Return true if a mulh[s|u] node for a
-    /// specific type is cheaper than a multiply followed by a shift.
-    /// This is true for words and doublewords on 64-bit PowerPC.
-    bool isMulhCheaperThanMulShift(EVT Type) const override;
-
     /// Override to support customized stack guard loading.
     bool useLoadStackGuardNode() const override;
     void insertSSPDeclarations(Module &M) const override;
Index: llvm/lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -1401,16 +1401,6 @@
   return VT.isScalarInteger();
 }
 
-/// isMulhCheaperThanMulShift - Return true if a mulh[s|u] node for a specific
-/// type is cheaper than a multiply followed by a shift.
-/// This is true for words and doublewords on 64-bit PowerPC.
-bool PPCTargetLowering::isMulhCheaperThanMulShift(EVT Type) const {
-  if (Subtarget.isPPC64() && (isOperationLegal(ISD::MULHS, Type) ||
-                              isOperationLegal(ISD::MULHU, Type)))
-    return true;
-  return TargetLowering::isMulhCheaperThanMulShift(Type);
-}
-
 const char *PPCTargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch ((PPCISD::NodeType)Opcode) {
   case PPCISD::FIRST_NUMBER:    break;
Index: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -354,6 +354,10 @@
     setOperationAction(ISD::ROTR, VT, Expand);
   }
 
+  // AArch64 doesn't have i32 MULH{S|U}.
+  setOperationAction(ISD::MULHU, MVT::i32, Expand);
+  setOperationAction(ISD::MULHS, MVT::i32, Expand);
+
   // AArch64 doesn't have {U|S}MUL_LOHI.
   setOperationAction(ISD::UMUL_LOHI, MVT::i64, Expand);
   setOperationAction(ISD::SMUL_LOHI, MVT::i64, Expand);
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4118,7 +4118,7 @@
 
   // If the type twice as wide is legal, transform the mulhs to a wider multiply
   // plus a shift.
-  if (!TLI.isMulhCheaperThanMulShift(VT) && VT.isSimple() && !VT.isVector()) {
+  if (!TLI.isOperationLegal(ISD::MULHS, VT)  && VT.isSimple() && !VT.isVector()) {
     MVT Simple = VT.getSimpleVT();
     unsigned SimpleSize = Simple.getSizeInBits();
     EVT NewVT = EVT::getIntegerVT(*DAG.getContext(), SimpleSize*2);
@@ -4174,7 +4174,7 @@
 
   // If the type twice as wide is legal, transform the mulhu to a wider multiply
   // plus a shift.
-  if (!TLI.isMulhCheaperThanMulShift(VT) && VT.isSimple() && !VT.isVector()) {
+  if (!TLI.isOperationLegal(ISD::MULHU, VT) && VT.isSimple() && !VT.isVector()) {
     MVT Simple = VT.getSimpleVT();
     unsigned SimpleSize = Simple.getSizeInBits();
     EVT NewVT = EVT::getIntegerVT(*DAG.getContext(), SimpleSize*2);
Index: llvm/include/llvm/CodeGen/TargetLowering.h
===================================================================
--- llvm/include/llvm/CodeGen/TargetLowering.h
+++ llvm/include/llvm/CodeGen/TargetLowering.h
@@ -1652,10 +1652,6 @@
 
   virtual bool isJumpTableRelative() const;
 
-  /// Return true if a mulh[s|u] node for a specific type is cheaper than
-  /// a multiply followed by a shift. This is false by default.
-  virtual bool isMulhCheaperThanMulShift(EVT Type) const { return false; }
-
   /// If a physical register, this specifies the register that
   /// llvm.savestack/llvm.restorestack should save and restore.
   unsigned getStackPointerRegisterToSaveRestore() const {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D80485.265903.patch
Type: text/x-patch
Size: 4103 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200524/8dcc750d/attachment-0001.bin>