Teach the ConstantMerge pass about alignment. Fixes PR10514!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136250 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/ConstantMerge.cpp b/lib/Transforms/IPO/ConstantMerge.cpp
index a21efce..c3ecb7a 100644
--- a/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/lib/Transforms/IPO/ConstantMerge.cpp
@@ -23,7 +23,9 @@
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
+#include "llvm/Target/TargetData.h"
#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
@@ -37,10 +39,18 @@
initializeConstantMergePass(*PassRegistry::getPassRegistry());
}
- // run - For this pass, process all of the globals in the module,
- // eliminating duplicate constants.
- //
+ // For this pass, process all of the globals in the module, eliminating
+ // duplicate constants.
bool runOnModule(Module &M);
+
+ // Return true iff we can determine the alignment of this global variable.
+ bool hasKnownAlignment(GlobalVariable *GV) const;
+
+ // Return the alignment of the global, including converting the default
+ // alignment to a concrete value.
+ unsigned getAlignment(GlobalVariable *GV) const;
+
+ const TargetData *TD;
};
}
@@ -77,15 +87,28 @@
return A.hasUnnamedAddr();
}
+bool ConstantMerge::hasKnownAlignment(GlobalVariable *GV) const {
+ return TD || GV->getAlignment() != 0;
+}
+
+unsigned ConstantMerge::getAlignment(GlobalVariable *GV) const {
+ if (TD)
+ return TD->getPreferredAlignment(GV);
+ return GV->getAlignment();
+}
+
bool ConstantMerge::runOnModule(Module &M) {
+ TD = getAnalysisIfAvailable<TargetData>();
+
// Find all the globals that are marked "used". These cannot be merged.
SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
FindUsedValues(M.getGlobalVariable("llvm.used"), UsedGlobals);
FindUsedValues(M.getGlobalVariable("llvm.compiler.used"), UsedGlobals);
- // Map unique constant/section pairs to globals. We don't want to merge
- // globals in different sections.
- DenseMap<Constant*, GlobalVariable*> CMap;
+ // Map unique <constants, has-unknown-alignment> pairs to globals. We don't
+ // want to merge globals of unknown alignment with those of explicit
+ // alignment. If we have TargetData, we always know the alignment.
+ DenseMap<PointerIntPair<Constant*, 1, bool>, GlobalVariable*> CMap;
// Replacements - This vector contains a list of replacements to perform.
SmallVector<std::pair<GlobalVariable*, GlobalVariable*>, 32> Replacements;
@@ -120,7 +143,8 @@
Constant *Init = GV->getInitializer();
// Check to see if the initializer is already known.
- GlobalVariable *&Slot = CMap[Init];
+ PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
+ GlobalVariable *&Slot = CMap[Pair];
// If this is the first constant we find or if the old on is local,
// replace with the current one. It the current is externally visible
@@ -152,7 +176,8 @@
Constant *Init = GV->getInitializer();
// Check to see if the initializer is already known.
- GlobalVariable *Slot = CMap[Init];
+ PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
+ GlobalVariable *Slot = CMap[Pair];
if (!Slot || Slot == GV)
continue;
@@ -175,6 +200,14 @@
// now. This avoid invalidating the pointers in CMap, which are unneeded
// now.
for (unsigned i = 0, e = Replacements.size(); i != e; ++i) {
+ // Bump the alignment if necessary.
+ if (Replacements[i].first->getAlignment() ||
+ Replacements[i].second->getAlignment()) {
+ Replacements[i].second->setAlignment(std::max(
+ Replacements[i].first->getAlignment(),
+ Replacements[i].second->getAlignment()));
+ }
+
// Eliminate any uses of the dead global.
Replacements[i].first->replaceAllUsesWith(Replacements[i].second);