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[LTO] Add SelectionKind to IRSymtab and use it in ld.lld/LLVMgold
In PGO, a C++ external linkage function `foo` has a private counter `__profc_foo` and a private `__profd_foo` in a `comdat nodeduplicate`. A `__attribute__((weak))` function `foo` has a weak hidden counter `__profc_foo` and a private `__profd_foo` in a `comdat nodeduplicate`. In `ld.lld a.o b.o`, say a.o defines an external linkage `foo` and b.o defines a weak `foo`. Currently we treat `comdat nodeduplicate` as `comdat any`, ld.lld will incorrectly consider `b.o:__profc_foo` non-prevailing. In the worst case when `b.o:__profd_foo` is retained and `b.o:__profc_foo` isn't, there will be dangling reference causing an `undefined hidden symbol` error. Add SelectionKind to `Comdat` in IRSymtab and let linkers ignore nodeduplicate comdat. Differential Revision: https://reviews.llvm.org/D106228
This commit is contained in:
Fangrui Song
parent
afd2d1339a
commit
2174d3b961
@ -119,7 +119,7 @@ private:
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StringRef TargetTriple, SourceFileName, COFFLinkerOpts;
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std::vector<StringRef> DependentLibraries;
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std::vector<StringRef> ComdatTable;
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std::vector<std::pair<StringRef, Comdat::SelectionKind>> ComdatTable;
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public:
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~InputFile();
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@ -172,7 +172,9 @@ public:
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StringRef getSourceFileName() const { return SourceFileName; }
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// Returns a table with all the comdats used by this file.
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ArrayRef<StringRef> getComdatTable() const { return ComdatTable; }
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ArrayRef<std::pair<StringRef, Comdat::SelectionKind>> getComdatTable() const {
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return ComdatTable;
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}
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// Returns the only BitcodeModule from InputFile.
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BitcodeModule &getSingleBitcodeModule();
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@ -26,6 +26,7 @@
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/ADT/iterator_range.h"
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#include "llvm/IR/Comdat.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/Object/SymbolicFile.h"
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#include "llvm/Support/Allocator.h"
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@ -80,6 +81,9 @@ struct Module {
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/// This is equivalent to an IR comdat.
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struct Comdat {
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Str Name;
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// llvm::Comdat::SelectionKind
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Word SelectionKind;
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};
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/// Contains the information needed by linkers for symbol resolution, as well as
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@ -132,7 +136,7 @@ struct Header {
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/// when the format changes, but it does not need to be incremented if a
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/// change to LLVM would cause it to create a different symbol table.
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Word Version;
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enum { kCurrentVersion = 2 };
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enum { kCurrentVersion = 3 };
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/// The producer's version string (LLVM_VERSION_STRING " " LLVM_REVISION).
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/// Consumers should rebuild the symbol table from IR if the producer's
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@ -280,11 +284,13 @@ public:
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StringRef getSourceFileName() const { return str(header().SourceFileName); }
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/// Returns a table with all the comdats used by this file.
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std::vector<StringRef> getComdatTable() const {
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std::vector<StringRef> ComdatTable;
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std::vector<std::pair<StringRef, llvm::Comdat::SelectionKind>>
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getComdatTable() const {
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std::vector<std::pair<StringRef, llvm::Comdat::SelectionKind>> ComdatTable;
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ComdatTable.reserve(Comdats.size());
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for (auto C : Comdats)
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ComdatTable.push_back(str(C.Name));
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ComdatTable.push_back({str(C.Name), llvm::Comdat::SelectionKind(
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uint32_t(C.SelectionKind))});
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return ComdatTable;
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}
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@ -199,6 +199,7 @@ Expected<int> Builder::getComdatIndex(const Comdat *C, const Module *M) {
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storage::Comdat Comdat;
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setStr(Comdat.Name, Saver.save(Name));
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Comdat.SelectionKind = C->getSelectionKind();
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Comdats.push_back(Comdat);
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}
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@ -18,7 +18,7 @@ define i32 @fun() {
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}
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; CHECK: D------X @fun2@8
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; CHECK-NEXT: comdat @fun2@8
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; CHECK-NEXT: comdat any @fun2@8
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$fun2 = comdat any
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define x86_fastcallcc i32 @fun2(i32 inreg %a, i32 inreg %b) comdat {
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entry:
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@ -52,7 +52,7 @@ entry:
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@g8 = common global i32 0, align 8
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; CHECK: D------- _g9
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; CHECK-NEXT: comdat _g9
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; CHECK-NEXT: comdat any _g9
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$g9 = comdat any
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@g9 = global i32 0, comdat
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@ -64,7 +64,12 @@ $g10 = comdat any
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; CHECK-NOT: comdat
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@g11 = global i32 0, comdat($g10)
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; CHECK: D------- _g12
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; CHECK-NEXT: comdat nodeduplicate _g12
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$g12 = comdat nodeduplicate
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@g12 = global i32 0, comdat
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; CHECK: D--WI--- _a1
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; CHECK-NEXT: comdat _g9
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; CHECK-NEXT: comdat any _g9
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; CHECK-NEXT: fallback _g9
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@a1 = weak alias i32, i32* @g9
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@ -9,13 +9,13 @@
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; BCA: <SYMTAB_BLOCK
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; Version stored at offset 0.
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; BCA-NEXT: <BLOB abbrevid=4/> blob data = '\x02\x00\x00\x00\x06\x00\x00\x00\x08\x00\x00\x00L\x00\x00\x00\x01\x00\x00\x00X\x00\x00\x00\x00\x00\x00\x00X\x00\x00\x00\x02\x00\x00\x00\x88\x00\x00\x00\x00\x00\x00\x00\x0E\x00\x00\x00\x18\x00\x00\x00&\x00\x00\x00\x0B\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x88\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x00$\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x08$\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00'
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; BCA-NEXT: <BLOB abbrevid=4/> blob data = '\x03\x00\x00\x00\x06\x00\x00\x00\x08\x00\x00\x00L\x00\x00\x00\x01\x00\x00\x00X\x00\x00\x00\x00\x00\x00\x00X\x00\x00\x00\x02\x00\x00\x00\x88\x00\x00\x00\x00\x00\x00\x00\x0E\x00\x00\x00\x18\x00\x00\x00&\x00\x00\x00\x0B\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x88\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x00$\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\xFF\xFF\xFF\xFF\x08$\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00\x03\x00\x00\x00'
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; BCA-NEXT: </SYMTAB_BLOCK>
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; BCA-NEXT: <STRTAB_BLOCK
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; BCA-NEXT: <BLOB abbrevid=4/> blob data = 'foobarproducerx86_64-unknown-linux-gnuirsymtab.ll'
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; BCA-NEXT: </STRTAB_BLOCK>
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; SYMTAB: version: 2
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; SYMTAB: version: 3
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; SYMTAB-NEXT: producer: producer
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; SYMTAB-NEXT: target triple: x86_64-unknown-linux-gnu
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; SYMTAB-NEXT: source filename: irsymtab.ll
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100
test/tools/gold/X86/comdat-nodeduplicate.ll
Normal file
100
test/tools/gold/X86/comdat-nodeduplicate.ll
Normal file
@ -0,0 +1,100 @@
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;; Keep __profd_foo in a nodeduplicate comdat, despite a comdat of the same name
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;; in a previous object file.
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;; Regular LTO
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; RUN: rm -rf %t && split-file %s %t
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; RUN: llvm-as %t/a.ll -o %t/a.bc
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; RUN: llvm-as %t/b.ll -o %t/b.bc
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; RUN: llvm-as %t/c.ll -o %t/c.bc
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; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext --plugin-opt=save-temps \
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; RUN: -u foo %t/a.bc --start-lib %t/b.bc --end-lib -o %t/ab
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; RUN: FileCheck %s --check-prefix=RESOL_AB < %t/ab.resolution.txt
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; RUN: llvm-readelf -x .data %t/ab | FileCheck %s --check-prefix=DATA
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; RESOL_AB: -r={{.*}}b.bc,__profc_foo,pl{{$}}
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;; .data contains a.bc:data. b.bc:data and c.bc:data are discarded.
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; DATA: 0x[[#%x,]] 01000000 00000000 ........
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;; __profc_foo from c.bc is non-prevailing and thus discarded.
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; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext --plugin-opt=save-temps \
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; RUN: -u foo -u c %t/a.bc --start-lib %t/b.bc %t/c.bc --end-lib -o %t/abc
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; RUN: FileCheck %s --check-prefix=RESOL_ABC < %t/abc.resolution.txt
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; RUN: llvm-readelf -x .data %t/abc | FileCheck %s --check-prefix=DATA
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; RESOL_ABC: -r={{.*}}b.bc,__profc_foo,pl{{$}}
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; RESOL_ABC: -r={{.*}}c.bc,__profc_foo,l{{$}}
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;; ThinLTO
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; RUN: rm -rf %t && split-file %s %t
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; RUN: opt --module-summary %t/a.ll -o %t/a.bc
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; RUN: opt --module-summary %t/b.ll -o %t/b.bc
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; RUN: opt --module-summary %t/c.ll -o %t/c.bc
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; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext \
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; RUN: -u foo %t/a.bc --start-lib %t/b.bc %t/c.bc --end-lib -o %t/abc
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; RUN: llvm-readelf -x .data %t/abc | FileCheck %s --check-prefix=DATA
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;--- a.ll
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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$__profc_foo = comdat nodeduplicate
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@__profc_foo = private global i64 1, comdat, align 8
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@__profd_foo = private global i64* @__profc_foo, comdat($__profc_foo), align 8
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declare void @b()
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define i64 @foo() {
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%v = load i64, i64* @__profc_foo
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%inc = add i64 1, %v
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store i64 %inc, i64* @__profc_foo
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ret i64 %inc
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}
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define void @_start() {
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call void @b()
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ret void
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}
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;--- b.ll
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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$__profc_foo = comdat nodeduplicate
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@__profc_foo = weak hidden global i64 2, comdat, align 8
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@__profd_foo = private global i64* @__profc_foo, comdat($__profc_foo)
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define weak i64 @foo() {
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%v = load i64, i64* @__profc_foo
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%inc = add i64 1, %v
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store i64 %inc, i64* @__profc_foo
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ret i64 %inc
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}
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define void @b() {
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ret void
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}
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;--- c.ll
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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$__profc_foo = comdat nodeduplicate
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@__profc_foo = weak hidden global i64 3, comdat, align 8
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@__profd_foo = private global i64* @__profc_foo, comdat($__profc_foo)
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define weak i64 @foo() {
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%v = load i64, i64* @__profc_foo
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%inc = add i64 1, %v
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store i64 %inc, i64* @__profc_foo
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ret i64 %inc
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}
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define void @c() {
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ret void
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}
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@ -623,8 +623,10 @@ static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
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sym.comdat_key = nullptr;
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int CI = Sym.getComdatIndex();
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if (CI != -1) {
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StringRef C = Obj->getComdatTable()[CI];
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sym.comdat_key = strdup(C.str().c_str());
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// Not setting comdat_key for nodeduplicate ensuress we don't deduplicate.
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std::pair<StringRef, Comdat::SelectionKind> C = Obj->getComdatTable()[CI];
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if (C.second != Comdat::NoDeduplicate)
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sym.comdat_key = strdup(C.first.str().c_str());
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}
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sym.resolution = LDPR_UNKNOWN;
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@ -418,7 +418,8 @@ static int dumpSymtab(int argc, char **argv) {
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outs() << '\n';
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}
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std::vector<StringRef> ComdatTable = Input->getComdatTable();
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ArrayRef<std::pair<StringRef, Comdat::SelectionKind>> ComdatTable =
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Input->getComdatTable();
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for (const InputFile::Symbol &Sym : Input->symbols()) {
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switch (Sym.getVisibility()) {
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case GlobalValue::HiddenVisibility:
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@ -447,8 +448,27 @@ static int dumpSymtab(int argc, char **argv) {
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<< Sym.getCommonAlignment() << '\n';
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int Comdat = Sym.getComdatIndex();
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if (Comdat != -1)
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outs() << " comdat " << ComdatTable[Comdat] << '\n';
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if (Comdat != -1) {
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outs() << " comdat ";
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switch (ComdatTable[Comdat].second) {
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case Comdat::Any:
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outs() << "any";
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break;
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case Comdat::ExactMatch:
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outs() << "exactmatch";
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break;
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case Comdat::Largest:
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outs() << "largest";
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break;
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case Comdat::NoDeduplicate:
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outs() << "nodeduplicate";
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break;
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case Comdat::SameSize:
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outs() << "samesize";
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break;
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}
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outs() << ' ' << ComdatTable[Comdat].first << '\n';
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}
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if (TT.isOSBinFormatCOFF() && Sym.isWeak() && Sym.isIndirect())
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outs() << " fallback " << Sym.getCOFFWeakExternalFallback() << '\n';
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