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[lld][WebAssembly] Allow relocations against non-live global symbols

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Just like the in case for function and data symbols this is needed to
support relocations in debug info sections which are allowed contains
relocations against non-live symbols.

The motivating use case is an object file that contains debug info that
references `__stack_pointer` (a local symbol) but does not actually
contain any uses of `__stack_pointer`.

Fixes: https://github.com/emscripten-core/emscripten/issues/14025

Differential Revision: https://reviews.llvm.org/D101399
This commit is contained in:
Sam Clegg 2021-04-27 13:45:10 -07:00
parent bf72f6bacc
commit 3e7bc0da57
3 changed files with 25 additions and 2 deletions
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23
lld/test/wasm/debuginfo-undefined-global.s Normal file
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@ -0,0 +1,23 @@
# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
# RUN: wasm-ld -o %t.wasm %t.o
# RUN: obj2yaml %t.wasm | FileCheck %s
# Debug sections are allowed to contains references to non-live symbols that
# then get GC'd. In this test the .debug_info seciton contains a reference to
# foo which is not otherwise used and will not be marked a live in the output.
# Verify the tombstone value is written to debug_info section.
.globl _start
_start:
.functype _start () -> ()
end_function
.section .debug_info,"",@
.int32 foo
.globaltype foo, i32
foo:
# CHECK: - Type: CUSTOM
# CHECK-NEXT: Name: .debug_info
# CHECK-NEXT: Payload: FFFFFFFF

2
lld/test/wasm/globals.s
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@ -1,4 +1,4 @@
# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
mm# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
# RUN: wasm-ld %t.o -o %t.wasm
# RUN: obj2yaml %t.wasm | FileCheck %s

2
lld/wasm/InputFiles.cpp
View File

@ -212,7 +212,7 @@ uint64_t ObjFile::calcNewValue(const WasmRelocation &reloc, uint64_t tombstone,
// so this will not produce a valid range conflicting with ranges of actual
// code. In other sections we return reloc.Addend.
if ((isa<FunctionSymbol>(sym) || isa<DataSymbol>(sym)) && !sym->isLive())
if (!isa<SectionSymbol>(sym) && !sym->isLive())
return tombstone ? tombstone : reloc.Addend;
}