[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 363499.
jrtc27 added a comment.

Fixed copy paste error in comment


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
@@ -161,8 +161,8 @@
 ; 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
@@ -520,7 +520,8 @@
                          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;
Index: llvm/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -2700,7 +2700,7 @@
 
 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());
 
@@ -2730,10 +2730,16 @@
     return SDValue(DAG.getMachineNode(RISCV::ADDI, DL, Ty, MNHi, AddrLo), 0);
   }
   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))).
+      return SDValue(DAG.getMachineNode(RISCV::PseudoLGA, DL, Ty, Addr), 0);
+
     // 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 SDValue(DAG.getMachineNode(RISCV::PseudoLLA, DL, Ty, Addr), 0);
   }
   }
@@ -2749,7 +2755,8 @@
 
   const GlobalValue *GV = N->getGlobal();
   bool IsLocal = getTargetMachine().shouldAssumeDSOLocal(*GV->getParent(), GV);
-  SDValue Addr = getAddr(N, DAG, IsLocal);
+  bool IsExternWeak = GV->hasExternalWeakLinkage();
+  SDValue Addr = getAddr(N, DAG, IsLocal, IsExternWeak);
 
   // In order to maximise the opportunity for common subexpression elimination,
   // emit a separate ADD node for the global address offset instead of folding


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