enhance jump threading to preserve TBAA information when PRE'ing loads,
fixing rdar://11039258, an issue that came up when inspecting clang's
bootstrapped codegen.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152635 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/Loads.cpp b/lib/Analysis/Loads.cpp
index 0e6bcbf..873a275 100644
--- a/lib/Analysis/Loads.cpp
+++ b/lib/Analysis/Loads.cpp
@@ -17,6 +17,7 @@
#include "llvm/GlobalAlias.h"
#include "llvm/GlobalVariable.h"
#include "llvm/IntrinsicInst.h"
+#include "llvm/LLVMContext.h"
#include "llvm/Operator.h"
using namespace llvm;
@@ -160,10 +161,15 @@
/// MaxInstsToScan specifies the maximum instructions to scan in the block. If
/// it is set to 0, it will scan the whole block. You can also optionally
/// specify an alias analysis implementation, which makes this more precise.
+///
+/// If TBAATag is non-null and a load or store is found, the TBAA tag from the
+/// load or store is recorded there. If there is no TBAA tag or if no access
+/// is found, it is left unmodified.
Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
BasicBlock::iterator &ScanFrom,
unsigned MaxInstsToScan,
- AliasAnalysis *AA) {
+ AliasAnalysis *AA,
+ MDNode **TBAATag) {
if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
// If we're using alias analysis to disambiguate get the size of *Ptr.
@@ -191,15 +197,19 @@
// (This is true even if the load is volatile or atomic, although
// those cases are unlikely.)
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
- if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
+ if (AreEquivalentAddressValues(LI->getOperand(0), Ptr)) {
+ if (TBAATag) *TBAATag = LI->getMetadata(LLVMContext::MD_tbaa);
return LI;
+ }
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
// If this is a store through Ptr, the value is available!
// (This is true even if the store is volatile or atomic, although
// those cases are unlikely.)
- if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
+ if (AreEquivalentAddressValues(SI->getOperand(1), Ptr)) {
+ if (TBAATag) *TBAATag = SI->getMetadata(LLVMContext::MD_tbaa);
return SI->getOperand(0);
+ }
// If Ptr is an alloca and this is a store to a different alloca, ignore
// the store. This is a trivial form of alias analysis that is important