diff options
author | David Majnemer <david.majnemer@gmail.com> | 2014-06-27 18:19:56 +0000 |
---|---|---|
committer | David Majnemer <david.majnemer@gmail.com> | 2014-06-27 18:19:56 +0000 |
commit | c8a1169c935ad9d3dfbdd4f72d80abf8f5acb03c (patch) | |
tree | ba02374e6ebac3aeaa3c234be27d92c6224cf34f /lib/Transforms/IPO/GlobalOpt.cpp | |
parent | 4a295dfbf9c5e8a71b8345484eff200058522b4e (diff) | |
download | llvm-c8a1169c935ad9d3dfbdd4f72d80abf8f5acb03c.tar.gz llvm-c8a1169c935ad9d3dfbdd4f72d80abf8f5acb03c.tar.bz2 llvm-c8a1169c935ad9d3dfbdd4f72d80abf8f5acb03c.tar.xz |
IR: Add COMDATs to the IR
This new IR facility allows us to represent the object-file semantic of
a COMDAT group.
COMDATs allow us to tie together sections and make the inclusion of one
dependent on another. This is required to implement features like MS
ABI VFTables and optimizing away certain kinds of initialization in C++.
This functionality is only representable in COFF and ELF, Mach-O has no
similar mechanism.
Differential Revision: http://reviews.llvm.org/D4178
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211920 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/IPO/GlobalOpt.cpp')
-rw-r--r-- | lib/Transforms/IPO/GlobalOpt.cpp | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp index 36c04f092b..dc9b2a8105 100644 --- a/lib/Transforms/IPO/GlobalOpt.cpp +++ b/lib/Transforms/IPO/GlobalOpt.cpp @@ -17,6 +17,7 @@ #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" #include "llvm/Analysis/ConstantFolding.h" @@ -1699,9 +1700,6 @@ static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { /// possible. If we make a change, return true. bool GlobalOpt::ProcessGlobal(GlobalVariable *GV, Module::global_iterator &GVI) { - if (!GV->isDiscardableIfUnused()) - return false; - // Do more involved optimizations if the global is internal. GV->removeDeadConstantUsers(); @@ -1944,6 +1942,13 @@ bool GlobalOpt::OptimizeFunctions(Module &M) { bool GlobalOpt::OptimizeGlobalVars(Module &M) { bool Changed = false; + + SmallSet<const Comdat *, 8> NotDiscardableComdats; + for (const GlobalVariable &GV : M.globals()) + if (const Comdat *C = GV.getComdat()) + if (!GV.isDiscardableIfUnused()) + NotDiscardableComdats.insert(C); + for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); GVI != E; ) { GlobalVariable *GV = GVI++; @@ -1958,7 +1963,12 @@ bool GlobalOpt::OptimizeGlobalVars(Module &M) { GV->setInitializer(New); } - Changed |= ProcessGlobal(GV, GVI); + if (GV->isDiscardableIfUnused()) { + if (const Comdat *C = GV->getComdat()) + if (NotDiscardableComdats.count(C)) + continue; + Changed |= ProcessGlobal(GV, GVI); + } } return Changed; } |