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[lld][WebAssembly] LTO: Use PIC reloc model with dynamic imports #165342

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Oct 28, 2025
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[lld][WebAssembly] LTO: Use PIC reloc model with dynamic imports #165342

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5 changes: 5 additions & 0 deletions lld/test/wasm/lto/relocation-model.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,11 @@
; RUN: wasm-ld %t.o -o %t_static.wasm -save-temps -r -mllvm -relocation-model=static
; RUN: llvm-readobj -r %t_static.wasm.lto.o | FileCheck %s --check-prefix=STATIC

;; Linking with --unresolved-symbols=import-dynamic should also generate PIC
;; code for external references.
; RUN: wasm-ld %t.o -o %t_import.wasm -save-temps --experimental-pic --unresolved-symbols=import-dynamic
; RUN: llvm-readobj -r %t_import.wasm.lto.o | FileCheck %s --check-prefix=PIC

; PIC: R_WASM_GLOBAL_INDEX_LEB foo
; STATIC: R_WASM_MEMORY_ADDR_LEB foo

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6 changes: 6 additions & 0 deletions lld/wasm/LTO.cpp
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Expand Up @@ -63,6 +63,12 @@ static lto::Config createConfig() {
c.RelocModel = std::nullopt;
else if (ctx.isPic)
c.RelocModel = Reloc::PIC_;
else if (ctx.arg.unresolvedSymbols == UnresolvedPolicy::ImportDynamic)
// With ImportDynamic we also need to use the PIC relocation model so that
// external symbols are references via the GOT.
// TODO(sbc): This should probably be Reloc::DynamicNoPIC, but the backend
// doesn't currently support that.
c.RelocModel = Reloc::PIC_;
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Do the docs for import-dynamic need to be updated?

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The documentatio already talks about how the input file need to be PIC.. so this is really just a bugfix I think. The code better matches the docs now.

else
c.RelocModel = Reloc::Static;

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