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When using -fsplit-lto-unit (explicitly specified or due to using -fsanitize=cfi/-fwhole-program-vtables), the emitted LLVM IR contains a module flag metadata `"EnableSplitLTOUnit"`. If a module contains both type metadata and `"EnableSplitLTOUnit"`, `ThinLTOBitcodeWriter.cpp` will write two modules into the bitcode file. Compiling the bitcode (not ThinLTO backend compilation) will lead to an error due to `parseIR` requiring a single module. ``` % clang -flto=thin a.cc -c -o a.bc % clang -c a.bc % clang -fsplit-lto-unit -flto=thin a.cc -c -o a.bc % clang -c a.bc error: Expected a single module 1 error generated. ``` There are multiple ways to have just one module in a bitcode file output: `-Xclang -fno-lto-unit`, not using features like `-fsanitize=cfi`, using `-fsanitize=cfi` with `-fno-split-lto-unit`. I think whether a bitcode input file contains 2 modules (internal implementation strategy) should not be a criterion to require an additional driver option when the user seek for a non-LTO compile action. Let's place the extra module (if present) into CodeGenOptions::LinkBitcodeFiles (originally for -cc1 -mlink-bitcode-file). Linker::linkModules will link the two modules together. This patch makes the following commands work: ``` clang -S -emit-llvm a.bc clang -S a.bc clang -c a.bc ``` Reviewed By: ormris Differential Revision: https://reviews.llvm.org/D154923
33 lines
1.0 KiB
C++
33 lines
1.0 KiB
C++
// REQUIRES: x86-registered-target
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/// When the input is a -fsplit-lto-unit bitcode file, link the regular LTO file like -mlink-bitcode-file.
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// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm-bc -flto=thin -flto-unit -fsplit-lto-unit %s -o %t.bc
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// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-obj %t.bc -o %t.o
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// RUN: llvm-nm %t.o | FileCheck %s
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// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm %t.bc -o - | FileCheck %s --check-prefix=CHECK-IR
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// CHECK: V _ZTI1A
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// CHECK-NEXT: V _ZTI1B
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// CHECK-NEXT: V _ZTS1A
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// CHECK-NEXT: V _ZTS1B
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// CHECK-NEXT: V _ZTV1A
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// CHECK-NEXT: V _ZTV1B
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// CHECK-IR-DAG: _ZTS1B = linkonce_odr constant
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// CHECK-IR-DAG: _ZTS1A = linkonce_odr constant
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// CHECK-IR-DAG: _ZTV1B = linkonce_odr unnamed_addr constant
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// CHECK-IR-DAG: _ZTI1A = linkonce_odr constant
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// CHECK-IR-DAG: _ZTI1B = linkonce_odr constant
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// CHECK-IR-DAG: _ZTV1A = linkonce_odr unnamed_addr constant
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struct A {
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virtual int c(int i) = 0;
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};
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struct B : A {
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virtual int c(int i) { return i; }
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};
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int use() {
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return (new B)->c(0);
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}
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