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[ELF] --warn-backrefs: save the referenced InputFile * 

For a diagnostic `A refers to B` where B refers to a bitcode file, if the
symbol gets optimized out, the user may see `A refers to <internal>`; if the
symbol is retained, the user may see `A refers to lto.tmp`.

Save the reference InputFile * in the DenseMap so that the original filename is
available in reportBackrefs().
This commit is contained in:
Fangrui Song 2020-10-22 15:26:52 -07:00
parent 3fbf9d10fd
commit ce3c5dae06
3 changed files with 40 additions and 5 deletions
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11
lld/ELF/Symbols.cpp
View File

@ -64,7 +64,8 @@ Defined *ElfSym::relaIpltStart;
Defined *ElfSym::relaIpltEnd;
Defined *ElfSym::riscvGlobalPointer;
Defined *ElfSym::tlsModuleBase;
DenseMap<const Symbol *, const InputFile *> elf::backwardReferences;
DenseMap<const Symbol *, std::pair<const InputFile *, const InputFile *>>
elf::backwardReferences;
static uint64_t getSymVA(const Symbol &sym, int64_t &addend) {
switch (sym.kind()) {
@ -377,7 +378,8 @@ void elf::reportBackrefs() {
for (auto &it : backwardReferences) {
const Symbol &sym = *it.first;
warn("backward reference detected: " + sym.getName() + " in " +
toString(it.second) + " refers to " + toString(sym.file));
toString(it.second.first) + " refers to " +
toString(it.second.second));
}
}
@ -532,9 +534,10 @@ void Symbol::resolveUndefined(const Undefined &other) {
// A traditional linker does not error for -ldef1 -lref -ldef2 (linking
// sandwich), where def2 may or may not be the same as def1. We don't want
// to warn for this case, so dismiss the warning if we see a subsequent lazy
// definition.
// definition. this->file needs to be saved because in the case of LTO it
// may be reset to nullptr or be replaced with a file named lto.tmp.
if (backref && !isWeak())
backwardReferences.try_emplace(this, other.file);
backwardReferences.try_emplace(this, std::make_pair(other.file, file));
return;
}

4
lld/ELF/Symbols.h
View File

@ -567,7 +567,9 @@ void reportBackrefs();
// A mapping from a symbol to an InputFile referencing it backward. Used by
// --warn-backrefs.
extern llvm::DenseMap<const Symbol *, const InputFile *> backwardReferences;
extern llvm::DenseMap<const Symbol *,
std::pair<const InputFile *, const InputFile *>>
backwardReferences;
} // namespace elf
} // namespace lld

30
lld/test/ELF/lto/warn-backrefs.ll Normal file
View File

@ -0,0 +1,30 @@
; REQUIRES: x86
;; Test that the referenced filename is correct (not <internal> or lto.tmp).
; RUN: split-file %s %t
; RUN: llvm-as %t/a.ll -o %ta.o
; RUN: llvm-as %t/b.ll -o %tb.o
; RUN: ld.lld --warn-backrefs --start-lib %tb.o --end-lib %ta.o 2>&1 | FileCheck %s
; CHECK: warning: backward reference detected: f in {{.*}}a.o refers to {{.*}}b.o
;--- a.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
declare void @f()
define void @_start() {
entry:
call void () @f()
ret void
}
;--- b.ll
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
define void @f() {
entry:
ret void
}