Introduce !align metadata for load instruction

Reviewed By: hfinkel

Differential Revision: http://reviews.llvm.org/D12853

llvm-svn: 248721

2 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 736077dc477..5481e722e53 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2979,6 +2979,11 @@ static bool isAligned(const Value *Base, APInt Offset, unsigned Align,
     BaseAlign = A->getParamAlignment();
   else if (auto CS = ImmutableCallSite(Base))
     BaseAlign = CS.getAttributes().getParamAlignment(AttributeSet::ReturnIndex);
+  else if (const LoadInst *LI = dyn_cast<LoadInst>(Base))
+    if (MDNode *MD = LI->getMetadata(LLVMContext::MD_align)) {
+      ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(0));
+      BaseAlign = CI->getLimitedValue();
+    }
 
   if (!BaseAlign) {
     Type *Ty = Base->getType()->getPointerElementType();
diff --git a/llvm/lib/IR/LLVMContext.cpp b/llvm/lib/IR/LLVMContext.cpp
index ee971c1be19..cecc6335ef1 100644
--- a/llvm/lib/IR/LLVMContext.cpp
+++ b/llvm/lib/IR/LLVMContext.cpp
@@ -123,6 +123,10 @@ LLVMContext::LLVMContext() : pImpl(new LLVMContextImpl(*this)) {
          "invariant.group kind id drifted");
   (void)InvariantGroupId;
 
+  // Create the 'align' metadata kind.
+  unsigned AlignID = getMDKindID("align");
+  assert(AlignID == MD_align && "align kind id drifted");
+  (void)AlignID;
 }
 LLVMContext::~LLVMContext() { delete pImpl; }