[llvm] [X86] Resolve TODO: Use Tokenfactor rather than the whole chain (PR #87002)

[via llvm-commits]

https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/87002

>From 5c4e9e996d4c910350d7956a53b6295251d45146 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Thu, 28 Mar 2024 15:34:14 -0400
Subject: [PATCH 1/2] [X86] Resolve TODO: Use Tokenfactor rather than the whole
 chain

---
 llvm/lib/Target/X86/X86SelectionDAGInfo.cpp | 43 +++++++++++----------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp b/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
index 7c630a2b0da080..0f46110f22dc93 100644
--- a/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
+++ b/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
@@ -67,7 +67,7 @@ SDValue X86SelectionDAGInfo::EmitTargetCodeForMemset(
   // The libc version is likely to be faster for these cases. It can use the
   // address value and run time information about the CPU.
   if (Alignment < Align(4) || !ConstantSize ||
-      ConstantSize->getZExtValue() > Subtarget.getMaxInlineSizeThreshold()) 
+      ConstantSize->getZExtValue() > Subtarget.getMaxInlineSizeThreshold())
     return SDValue();
 
   uint64_t SizeVal = ConstantSize->getZExtValue();
@@ -128,26 +128,29 @@ SDValue X86SelectionDAGInfo::EmitTargetCodeForMemset(
   InGlue = Chain.getValue(1);
 
   SDVTList Tys = DAG.getVTList(MVT::Other, MVT::Glue);
-  SDValue Ops[] = { Chain, DAG.getValueType(AVT), InGlue };
-  Chain = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops);
-
-  if (BytesLeft) {
-    // Handle the last 1 - 7 bytes.
-    unsigned Offset = SizeVal - BytesLeft;
-    EVT AddrVT = Dst.getValueType();
-    EVT SizeVT = Size.getValueType();
-
-    Chain =
-        DAG.getMemset(Chain, dl,
-                      DAG.getNode(ISD::ADD, dl, AddrVT, Dst,
-                                  DAG.getConstant(Offset, dl, AddrVT)),
-                      Val, DAG.getConstant(BytesLeft, dl, SizeVT), Alignment,
-                      isVolatile, AlwaysInline,
-                      /* isTailCall */ false, DstPtrInfo.getWithOffset(Offset));
-  }
+  SDValue Ops[] = {Chain, DAG.getValueType(AVT), InGlue};
+  SDValue RepStos = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops);
+
+  /// RepStos can process the whole length.
+  if (BytesLeft == 0)
+    return RepStos;
 
-  // TODO: Use a Tokenfactor, as in memcpy, instead of a single chain.
-  return Chain;
+  // Handle the last 1 - 7 bytes.
+  SmallVector<SDValue, 4> Results;
+  Results.push_back(RepStos);
+  unsigned Offset = SizeVal - BytesLeft;
+  EVT AddrVT = Dst.getValueType();
+  EVT SizeVT = Size.getValueType();
+
+  Results.push_back(
+      DAG.getMemset(Chain, dl,
+                    DAG.getNode(ISD::ADD, dl, AddrVT, Dst,
+                                DAG.getConstant(Offset, dl, AddrVT)),
+                    Val, DAG.getConstant(BytesLeft, dl, SizeVT), Alignment,
+                    isVolatile, AlwaysInline,
+                    /* isTailCall */ false, DstPtrInfo.getWithOffset(Offset)));
+
+  return DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Results);
 }
 
 /// Emit a single REP MOVS{B,W,D,Q} instruction.

>From 0596ef7106328fe7219aa946ade85b730e47a11b Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Thu, 28 Mar 2024 17:23:10 -0400
Subject: [PATCH 2/2] Update X86SelectionDAGInfo.cpp

---
 llvm/lib/Target/X86/X86SelectionDAGInfo.cpp | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp b/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
index 0f46110f22dc93..8b2d6316560863 100644
--- a/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
+++ b/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
@@ -48,19 +48,18 @@ SDValue X86SelectionDAGInfo::EmitTargetCodeForMemset(
     SelectionDAG &DAG, const SDLoc &dl, SDValue Chain, SDValue Dst, SDValue Val,
     SDValue Size, Align Alignment, bool isVolatile, bool AlwaysInline,
     MachinePointerInfo DstPtrInfo) const {
+  // If to a segment-relative address space, use the default lowering.
+  if (DstPtrInfo.getAddrSpace() >= 256)
+    return SDValue();
+
   ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);
   const X86Subtarget &Subtarget =
       DAG.getMachineFunction().getSubtarget<X86Subtarget>();
 
-#ifndef NDEBUG
   // If the base register might conflict with our physical registers, bail out.
   const MCPhysReg ClobberSet[] = {X86::RCX, X86::RAX, X86::RDI,
                                   X86::ECX, X86::EAX, X86::EDI};
-  assert(!isBaseRegConflictPossible(DAG, ClobberSet));
-#endif
-
-  // If to a segment-relative address space, use the default lowering.
-  if (DstPtrInfo.getAddrSpace() >= 256)
+  if (isBaseRegConflictPossible(DAG, ClobberSet))
     return SDValue();
 
   // If not DWORD aligned or size is more than the threshold, call the library.