[X86] Fix tls variable lowering issue with large code model

Summary:
The problem here is the lowering for tls variable. Below is the DAG for the code.
SelectionDAG has 11 nodes:

t0: ch = EntryToken
      t8: i64,ch = load<(load 8 from `i8 addrspace(257)* null`, addrspace 257)> t0, Constant:i64<0>, undef:i64
        t10: i64 = X86ISD::WrapperRIP TargetGlobalTLSAddress:i64<i32* @x> 0 [TF=10]
      t11: i64,ch = load<(load 8 from got)> t0, t10, undef:i64
    t12: i64 = add t8, t11
  t4: i32,ch = load<(dereferenceable load 4 from @x)> t0, t12, undef:i64
t6: ch = CopyToReg t0, Register:i32 %0, t4
And when mcmodel is large, below instruction can NOT be folded.

  t10: i64 = X86ISD::WrapperRIP TargetGlobalTLSAddress:i64<i32* @x> 0 [TF=10]
t11: i64,ch = load<(load 8 from got)> t0, t10, undef:i64
So "t11: i64,ch = load<(load 8 from got)> t0, t10, undef:i64" is lowered to " Morphed node: t11: i64,ch = MOV64rm<Mem:(load 8 from got)> t10, TargetConstant:i8<1>, Register:i64 $noreg, TargetConstant:i32<0>, Register:i32 $noreg, t0"

When llvm start to lower "t10: i64 = X86ISD::WrapperRIP TargetGlobalTLSAddress:i64<i32* @x> 0 [TF=10]", it fails.

The patch is to fold the load and X86ISD::WrapperRIP.

Fixes PR26906

Patch by LuoYuanke

Reviewers: craig.topper, rnk, annita.zhang, wxiao3

Reviewed By: rnk

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58336

llvm-svn: 354756

1 files changed, 13 insertions, 5 deletions

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 25fb5d74698..5f051b39cd5 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1137,15 +1137,23 @@ bool X86DAGToDAGISel::matchWrapper(SDValue N, X86ISelAddressMode &AM) {
   if (AM.hasSymbolicDisplacement())
     return true;
 
+  bool IsRIPRelTLS = false;
   bool IsRIPRel = N.getOpcode() == X86ISD::WrapperRIP;
+  if (IsRIPRel) {
+    SDValue Val = N.getOperand(0);
+    if (Val.getOpcode() == ISD::TargetGlobalTLSAddress)
+      IsRIPRelTLS = true;
+  }
 
-  // We can't use an addressing mode in the 64-bit large code model. In the
-  // medium code model, we use can use an mode when RIP wrappers are present.
-  // That signifies access to globals that are known to be "near", such as the
-  // GOT itself.
+  // We can't use an addressing mode in the 64-bit large code model.
+  // Global TLS addressing is an exception. In the medium code model,
+  // we use can use a mode when RIP wrappers are present.
+  // That signifies access to globals that are known to be "near",
+  // such as the GOT itself.
   CodeModel::Model M = TM.getCodeModel();
   if (Subtarget->is64Bit() &&
-      (M == CodeModel::Large || (M == CodeModel::Medium && !IsRIPRel)))
+      ((M == CodeModel::Large && !IsRIPRelTLS) ||
+       (M == CodeModel::Medium && !IsRIPRel)))
     return true;
 
   // Base and index reg must be 0 in order to use %rip as base.