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Bill Wendling a20689fd7e It's possible for two types, which are isomorphic, to be added to the
destination module, but one of them isn't used in the destination module. If
another module comes along and the uses the unused type, there could be type
conflicts when the modules are finally linked together. (This happened when
building LLVM.)

The test that was reduced is:

Module A:

%Z = type { %A }
%A = type { %B.1, [7 x x86_fp80] }
%B.1 = type { %C }
%C = type { i8* }

declare void @func_x(%C*, i64, i64)
declare void @func_z(%Z* nocapture)

Module B:

%B = type { %C.1 }
%C.1 = type { i8* }
%A.2 = type { %B.3, [5 x x86_fp80] }
%B.3 = type { %C.1 }

define void @func_z() {
  %x = alloca %A.2, align 16
  %y = getelementptr inbounds %A.2* %x, i64 0, i32 0, i32 0
  call void @func_x(%C.1* %y, i64 37, i64 927) nounwind
  ret void
}

declare void @func_x(%C.1*, i64, i64)
declare void @func_y(%B* nocapture)

(Unfortunately, this test doesn't fail under llvm-link, only during an LTO
linking.) The '%C' and '%C.1' clash. The destination module gets the '%C'
declaration. When merging Module B, it looks at the '%C.1' subtype of the '%B'
structure. It adds that in, because that's cool. And when '%B.3' is processed,
it uses the '%C.1'. But the '%B' has used '%C' and we prefer to use '%C'. So the
'@func_x' type is changed to 'void (%C*, i64, i64)', but the type of '%x' in
'@func_z' remains '%A.2'. The GEP resolves to a '%C.1', which conflicts with the
'@func_x' signature.

We can resolve this situation by making sure that the type is used in the
destination before saying that it should be used in the module being merged in.

With this fix, LLVM and Clang both compile under LTO.
<rdar://problem/10913281>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153351 91177308-0d34-0410-b5e6-96231b3b80d8
2012-03-23 23:17:38 +00:00
autoconf Remove the C backend. 2012-03-23 05:50:46 +00:00
bindings [python] Add negative MemoryBuffer testcase 2012-03-22 11:23:52 +00:00
cmake Minimal changes for LLVM to compile under VS11. 2012-03-01 22:42:52 +00:00
docs Remove the C backend. 2012-03-23 05:50:46 +00:00
examples Switch to a more idiomatic way of silencing unused variable warnings in 2012-02-20 00:02:49 +00:00
include Add a hook in MCELFObjectTargetWriter to allow targets to sort relocation 2012-03-23 23:06:45 +00:00
lib It's possible for two types, which are isomorphic, to be added to the 2012-03-23 23:17:38 +00:00
projects Remove the C backend. 2012-03-23 05:50:46 +00:00
runtime Fixing a warning in MSVC (this is also a test commit) 2012-02-05 19:43:39 +00:00
test Don't convert objc_retainAutoreleasedReturnValue to objc_retain if it 2012-03-23 18:09:00 +00:00
tools Include cctype for std::isprint. 2012-03-23 11:49:32 +00:00
unittests Revert a series of commits to MCJIT to get the build working in CMake 2012-03-22 05:44:06 +00:00
utils Include cstdio in a few place that depended on getting it transitively through StringExtras.h 2012-03-23 11:35:30 +00:00
.gitignore git: Add tools/lldb to the ignore list. 2011-11-10 22:55:50 +00:00
CMakeLists.txt Remove the C backend. 2012-03-23 05:50:46 +00:00
configure Remove the C backend. 2012-03-23 05:50:46 +00:00
CREDITS.TXT sort by alpha. 2012-03-12 21:12:59 +00:00
LICENSE.TXT Happy new year 2012! 2012-01-01 08:16:56 +00:00
llvm.spec.in Tidy up. s/Low Level Virtual Machine/LLVM/. 2012-01-25 22:00:23 +00:00
LLVMBuild.txt LLVMBuild: Introduce a common section which currently has a list of the 2011-12-12 22:45:54 +00:00
Makefile Makefile: add missing files to FilesToConfig 2012-01-17 02:56:49 +00:00
Makefile.common Removed trailing whitespace from Makefiles. 2009-01-09 16:44:42 +00:00
Makefile.config.in Add profiling support for Intel Parallel Amplifier XE (VTune) for JITted code in LLVM. 2012-03-13 08:33:15 +00:00
Makefile.rules Use a posix compliant regexp in export file construction. 2012-03-12 20:58:14 +00:00
README.txt test commit 2012-03-20 13:12:38 +00:00

Low Level Virtual Machine (LLVM)
================================

This directory and its subdirectories contain source code for the Low Level
Virtual Machine, a toolkit for the construction of highly optimized compilers,
optimizers, and runtime environments.

LLVM is open source software. You may freely distribute it under the terms of
the license agreement found in LICENSE.txt.

Please see the HTML documentation provided in docs/index.html for further
assistance with LLVM.

If you're writing a package for LLVM, see docs/Packaging.html for our
suggestions.