[PATCH] D107280: [RISCV] Lower extern_weak symbols using the GOT for the medany model

[Jessica Clarke via Phabricator via llvm-commits]

jrtc27 updated this revision to Diff 447492.
jrtc27 added a comment.

Rebased, including to use riscv_lga ISD node instead and create a memop like for la


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107280/new/

https://reviews.llvm.org/D107280

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/lib/Target/RISCV/RISCVISelLowering.h
  llvm/test/CodeGen/RISCV/codemodel-lowering.ll


Index: llvm/test/CodeGen/RISCV/codemodel-lowering.ll
===================================================================
--- llvm/test/CodeGen/RISCV/codemodel-lowering.ll
+++ llvm/test/CodeGen/RISCV/codemodel-lowering.ll
@@ -157,8 +157,8 @@
 ; RV32I-MEDIUM-LABEL: lower_extern_weak:
 ; RV32I-MEDIUM:       # %bb.0:
 ; RV32I-MEDIUM-NEXT:  .LBB4_1: # Label of block must be emitted
-; RV32I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(W)
-; RV32I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.LBB4_1)
+; RV32I-MEDIUM-NEXT:    auipc a0, %got_pcrel_hi(W)
+; RV32I-MEDIUM-NEXT:    lw a0, %pcrel_lo(.LBB4_1)(a0)
 ; RV32I-MEDIUM-NEXT:    lw a0, 0(a0)
 ; RV32I-MEDIUM-NEXT:    ret
   %1 = load volatile i32, i32* @W
Index: llvm/lib/Target/RISCV/RISCVISelLowering.h
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.h
+++ llvm/lib/Target/RISCV/RISCVISelLowering.h
@@ -623,7 +623,8 @@
                          RISCVCCAssignFn Fn) const;
 
   template <class NodeTy>
-  SDValue getAddr(NodeTy *N, SelectionDAG &DAG, bool IsLocal = true) const;
+  SDValue getAddr(NodeTy *N, SelectionDAG &DAG, bool IsLocal = true,
+                  bool IsExternWeak = false) const;
   SDValue getStaticTLSAddr(GlobalAddressSDNode *N, SelectionDAG &DAG,
                            bool UseGOT) const;
   SDValue getDynamicTLSAddr(GlobalAddressSDNode *N, SelectionDAG &DAG) const;
Index: llvm/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -3686,7 +3686,7 @@
 
 template <class NodeTy>
 SDValue RISCVTargetLowering::getAddr(NodeTy *N, SelectionDAG &DAG,
-                                     bool IsLocal) const {
+                                     bool IsLocal, bool IsExternWeak) const {
   SDLoc DL(N);
   EVT Ty = getPointerTy(DAG.getDataLayout());
 
@@ -3725,10 +3725,27 @@
     return DAG.getNode(RISCVISD::ADD_LO, DL, Ty, MNHi, AddrLo);
   }
   case CodeModel::Medium: {
+    SDValue Addr = getTargetNode(N, DL, Ty, DAG, 0);
+    if (IsExternWeak) {
+      // Extern weak symbols must be addressed indirectly as 0 may not be
+      // within 2GiB of PC. This generates the pattern (PseudoLGA sym), which
+      // expands to (ld (addi (auipc %got_pcrel_hi(sym)) %pcrel_lo(auipc))).
+      MachineFunction &MF = DAG.getMachineFunction();
+      MachineMemOperand *MemOp = MF.getMachineMemOperand(
+          MachinePointerInfo::getGOT(MF),
+          MachineMemOperand::MOLoad | MachineMemOperand::MODereferenceable |
+              MachineMemOperand::MOInvariant,
+          LLT(Ty.getSimpleVT()), Align(Ty.getFixedSizeInBits() / 8));
+      SDValue Load =
+          DAG.getMemIntrinsicNode(RISCVISD::LGA, DL,
+                                  DAG.getVTList(Ty, MVT::Other),
+                                  {DAG.getEntryNode(), Addr}, Ty, MemOp);
+      return Load;
+    }
+
     // Generate a sequence for accessing addresses within any 2GiB range within
     // the address space. This generates the pattern (PseudoLLA sym), which
     // expands to (addi (auipc %pcrel_hi(sym)) %pcrel_lo(auipc)).
-    SDValue Addr = getTargetNode(N, DL, Ty, DAG, 0);
     return DAG.getNode(RISCVISD::LLA, DL, Ty, Addr);
   }
   }
@@ -3739,7 +3756,8 @@
   SDLoc DL(Op);
   GlobalAddressSDNode *N = cast<GlobalAddressSDNode>(Op);
   assert(N->getOffset() == 0 && "unexpected offset in global node");
-  return getAddr(N, DAG, N->getGlobal()->isDSOLocal());
+  const GlobalValue *GV = N->getGlobal();
+  return getAddr(N, DAG, GV->isDSOLocal(), GV->hasExternalWeakLinkage());
 }
 
 SDValue RISCVTargetLowering::lowerBlockAddress(SDValue Op,


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