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[llvm][EmbedBitcodePass] Prevent modifying the module with ThinLTO #139999

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Merged
merged 1 commit into from
May 29, 2025
Merged

[llvm][EmbedBitcodePass] Prevent modifying the module with ThinLTO #139999

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6 changes: 5 additions & 1 deletion llvm/lib/Transforms/IPO/EmbedBitcodePass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
#include "llvm/Support/raw_ostream.h"
#include "llvm/TargetParser/Triple.h"
#include "llvm/Transforms/IPO/ThinLTOBitcodeWriter.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"

#include <string>
Expand All @@ -33,8 +34,11 @@ PreservedAnalyses EmbedBitcodePass::run(Module &M, ModuleAnalysisManager &AM) {

std::string Data;
raw_string_ostream OS(Data);
// Clone the module with Thin LTO, since ThinLTOBitcodeWriterPass changes
// vtable linkage that would break the non-lto object code for FatLTO.
if (IsThinLTO)
ThinLTOBitcodeWriterPass(OS, /*ThinLinkOS=*/nullptr).run(M, AM);
ThinLTOBitcodeWriterPass(OS, /*ThinLinkOS=*/nullptr)
.run(*llvm::CloneModule(M), AM);
else
BitcodeWriterPass(OS, /*ShouldPreserveUseListOrder=*/false, EmitLTOSummary)
.run(M, AM);
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7 changes: 4 additions & 3 deletions llvm/test/Transforms/EmbedBitcode/embed-wpd.ll
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@@ -1,12 +1,13 @@
; RUN: opt --mtriple x86_64-unknown-linux-gnu < %s -passes="embed-bitcode<thinlto>" -S | FileCheck %s

; CHECK-NOT: $_ZTV3Foo = comdat any
; CHECK: $_ZTV3Foo = comdat any
$_ZTV3Foo = comdat any

$_ZTI3Foo = comdat any

; CHECK: @_ZTV3Foo = external hidden unnamed_addr constant { [5 x ptr] }, align 8
; CHECK: @_ZTI3Foo = linkonce_odr hidden constant { ptr, ptr, ptr } { ptr getelementptr inbounds (ptr, ptr @_ZTVN10__cxxabiv120__si_class_type_infoE, i64 2), ptr @_ZTS3Foo, ptr @_ZTISt13runtime_error }, comdat, align 8
;; ThinLTOBitcodeWriter will remove the vtable for Foo, and make it an external symbol
; CHECK: @_ZTV3Foo = linkonce_odr hidden unnamed_addr constant { [5 x ptr] } { [5 x ptr] [ptr null, ptr @_ZTI3Foo, ptr @_ZN3FooD2Ev, ptr @_ZN3FooD0Ev, ptr @_ZNKSt13runtime_error4whatEv] }, comdat, align 8, !type !0, !type !1, !type !2, !type !3, !type !4, !type !5
; CHECK-NOT: @foo = external unnamed_addr constant { [5 x ptr] }, align 8
; CHECK: @llvm.embedded.object = private constant {{.*}}, section ".llvm.lto", align 1
; CHECK: @llvm.compiler.used = appending global [1 x ptr] [ptr @llvm.embedded.object], section "llvm.metadata"
@_ZTV3Foo = linkonce_odr hidden unnamed_addr constant { [5 x ptr] } { [5 x ptr] [ptr null, ptr @_ZTI3Foo, ptr @_ZN3FooD2Ev, ptr @_ZN3FooD0Ev, ptr @_ZNKSt13runtime_error4whatEv] }, comdat, align 8, !type !0, !type !1, !type !2, !type !3, !type !4, !type !5
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