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LowerBitSets: Ignore bitset entries that do not directly refer to a global.

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It is possible for a global to be substituted with another global of a
different type or a different kind (i.e. an alias) at IR link time. One
example of this scenario is when a Microsoft ABI vtable is substituted with
an alias referring to a larger vtable containing an RTTI reference.

This will cause the global to be RAUW'd with a possibly bitcasted reference
to the other global. This will of course also affect any references to the
global in bitset metadata.

The right way to handle such metadata is simply to ignore it. This is sound
because the linked module should contain another copy of the bitset entries as
applied to the new global.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240866 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne
2015-06-27 00:17:51 +00:00
parent 4f95bcc836
commit e92934e078
2 changed files with 26 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
lib/Transforms/IPO/LowerBitSets.cpp
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@@ -271,8 +271,10 @@ BitSetInfo LowerBitSets::buildBitSet(
for (MDNode *Op : BitSetNM->operands()) {
if (Op->getOperand(0) != BitSet || !Op->getOperand(1))
continue;
auto OpGlobal = cast<GlobalVariable>(
auto OpGlobal = dyn_cast<GlobalVariable>(
cast<ConstantAsMetadata>(Op->getOperand(1))->getValue());
if (!OpGlobal)
continue;
uint64_t Offset =
cast<ConstantInt>(cast<ConstantAsMetadata>(Op->getOperand(2))
->getValue())->getZExtValue();
@@ -621,7 +623,7 @@ bool LowerBitSets::buildBitSets() {
report_fatal_error("Bit set element must be a constant");
auto OpGlobal = dyn_cast<GlobalVariable>(OpConstMD->getValue());
if (!OpGlobal)
report_fatal_error("Bit set element must refer to global");
continue;
auto OffsetConstMD = dyn_cast<ConstantAsMetadata>(Op->getOperand(2));
if (!OffsetConstMD)
@@ -675,8 +677,10 @@ bool LowerBitSets::buildBitSets() {
if (I == BitSetIndices.end())
continue;
auto OpGlobal = cast<GlobalVariable>(
auto OpGlobal = dyn_cast<GlobalVariable>(
cast<ConstantAsMetadata>(Op->getOperand(1))->getValue());
if (!OpGlobal)
continue;
BitSetMembers[I->second].insert(GlobalIndices[OpGlobal]);
}
}