[llvm] [X86] Don't fold loads from non-fixed stack objects into tail calls (PR #221243)

[Akash Manna via llvm-commits]

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@@ -3682,7 +3683,40 @@ static bool mayUseCarryFlag(X86::CondCode CC) {
   return true;
 }
 
+/// Return true if \p Addr may be matched with a non-fixed frame index as base.
+static bool addrMayUseNonFixedFrameIndex(SDValue Addr,
+                                         const MachineFrameInfo &MFI,
+                                         unsigned Depth = 0) {
+  if (auto *FI = dyn_cast<FrameIndexSDNode>(Addr))
+    return !MFI.isFixedObjectIndex(FI->getIndex());
+  // Assume the worst if we can't see the whole address expression.
+  if (Depth >= SelectionDAG::MaxRecursionDepth)
+    return true;
+  switch (Addr.getOpcode()) {
+  case ISD::ADD:
+  case ISD::OR:
+  case ISD::XOR:
+    return addrMayUseNonFixedFrameIndex(Addr.getOperand(0), MFI, Depth + 1) ||
+           addrMayUseNonFixedFrameIndex(Addr.getOperand(1), MFI, Depth + 1);
+  case ISD::SUB:
+    return addrMayUseNonFixedFrameIndex(Addr.getOperand(0), MFI, Depth + 1);
+  default:
+    // Only add-like nodes and the LHS of a SUB can fold a frame index into the
+    // base; anything else is matched as a register or symbol base.
+    return false;
+  }
+}
+
 bool X86DAGToDAGISel::checkTCRetEnoughRegs(SDNode *N) const {
+  assert(N->getOpcode() == X86ISD::TC_RETURN);
+  // X86tcret args: (*chain, ptr, imm, regs..., glue)
+  auto *Load = cast<LoadSDNode>(N->getOperand(1));
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akash-manna-sky wrote:

moved the original `BasePtr` line up and dropped the `Load` temporary.


https://github.com/llvm/llvm-project/pull/221243