Revert "Stop increasing alignment of externally-visible globals on ELF platforms."

This reverts commit r257719, due to PR26144.

llvm-svn: 257775

1 files changed, 13 insertions, 7 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 91b3499407c..d2793e5ecb5 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -944,31 +944,37 @@ bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
 static unsigned enforceKnownAlignment(Value *V, unsigned Align,
                                       unsigned PrefAlign,
                                       const DataLayout &DL) {
-  assert(PrefAlign > Align);
-
   V = V->stripPointerCasts();
 
   if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
-    assert(AI->getAlignment() <= Align);
     // If the preferred alignment is greater than the natural stack alignment
     // then don't round up. This avoids dynamic stack realignment.
     if (DL.exceedsNaturalStackAlignment(PrefAlign))
       return Align;
+    // If there is a requested alignment and if this is an alloca, round up.
+    if (AI->getAlignment() >= PrefAlign)
+      return AI->getAlignment();
     AI->setAlignment(PrefAlign);
     return PrefAlign;
   }
 
   if (auto *GO = dyn_cast<GlobalObject>(V)) {
-    assert(GO->getAlignment() <= Align);
     // If there is a large requested alignment and we can, bump up the alignment
     // of the global.  If the memory we set aside for the global may not be the
     // memory used by the final program then it is impossible for us to reliably
     // enforce the preferred alignment.
-    if (!GO->canIncreaseAlignment())
+    if (!GO->isStrongDefinitionForLinker())
       return Align;
 
-    GO->setAlignment(PrefAlign);
-    return PrefAlign;
+    if (GO->getAlignment() >= PrefAlign)
+      return GO->getAlignment();
+    // We can only increase the alignment of the global if it has no alignment
+    // specified or if it is not assigned a section.  If it is assigned a
+    // section, the global could be densely packed with other objects in the
+    // section, increasing the alignment could cause padding issues.
+    if (!GO->hasSection() || GO->getAlignment() == 0)
+      GO->setAlignment(PrefAlign);
+    return GO->getAlignment();
   }
 
   return Align;