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Don't upgrade global constructors when reading bitcode

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An optional third field was added to `llvm.global_ctors` (and
`llvm.global_dtors`) in r209015.  Most of the code has been changed to
deal with both versions of the variables.  Users of the C API might
create either version, the helper functions in LLVM create the two-field
version, and clang now creates the three-field version.

However, the BitcodeReader was changed to always upgrade to the
three-field version.  This created an unnecessary inconsistency in the
IR before/after serializing to bitcode.

This commit resolves the inconsistency by making the third field truly
optional (and not upgrading in the bitcode reader).  Since `llvm-link`
was relying on this upgrade code, rather than deleting it I've moved it
into `ModuleLinker`, where it upgrades these arrays as necessary to
resolve inconsistencies between modules.

The ideal resolution would be to remove the 2-field version and make the
third field required.  I filed PR20506 to track that.

I changed `test/Bitcode/upgrade-global-ctors.ll` to a negative test and
duplicated the `llvm-link` check in `test/Linker/global_ctors.ll` to
check both upgrade directions.

Since I came across this as part of PR5680 (serializing use-list order),
I've also added the missing `verify-uselistorder` RUN line to
`test/Bitcode/metadata-2.ll`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215457 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith
2014-08-12 16:46:37 +00:00
parent 01c6ad07d2
commit 49135bb76c
5 changed files with 87 additions and 56 deletions
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1
test/Bitcode/metadata-2.ll
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@@ -1,4 +1,5 @@
; RUN: llvm-as < %s | llvm-dis -disable-output
; RUN: verify-uselistorder < %s -preserve-bc-use-list-order
%0 = type { %object.ModuleInfo.__vtbl*, i8*, %"byte[]", %1, %"ClassInfo[]", i32, void ()*, void ()*, void ()*, i8*, void ()* } ; type %0
%1 = type { i64, %object.ModuleInfo* } ; type %1
%2 = type { i32, void ()* } ; type %2

3
test/Bitcode/upgrade-global-ctors.ll
View File

@@ -1,4 +1,5 @@
; RUN: llvm-dis < %s.bc| FileCheck %s
; RUN: verify-uselistorder < %s.bc -preserve-bc-use-list-order
; CHECK: @llvm.global_ctors = appending global [0 x { i32, void ()*, i8* }] zeroinitializer
; Global constructors should no longer be upgraded when reading bitcode.
; CHECK: @llvm.global_ctors = appending global [0 x { i32, void ()* }] zeroinitializer