InstCombine: propagate nonNull through assume

[artagnon]

Summary

Make assume (load (call|invoke) != null) set nonNull return attribute
for the call and invoke. Also include tests.

[artagnon]

ping! (How) should I write a test for this?

[hfinkel]

In D7107#119587, @artagnon wrote:

ping! (How) should I write a test for this?

I think you'd add tests for the nonnull attribute in a similar way to how we test for the nonnull metadata in test/Transforms/InstCombine/assume.ll.

lib/Transforms/InstCombine/InstCombineCalls.cpp

1137

This does not seem right. dereferenceable needs a size.

[artagnon]

Drop the deref propagation, because it requires more work. Redo the
nonNull propagation so that it is correct (thanks to Hal for poking me
to test it properly).

[hfinkel]

LGTM.

lib/Transforms/InstCombine/InstCombineCalls.cpp

1078

Line too long?

lib/Transforms/InstCombine/InstCombineCalls.cpp

case Intrinsic::assume: {
     if (match(IIOperand, m_Not(m_Or(m_Value(A), m_Value(B))))) {
       Builder->CreateCall(AssumeIntrinsic, Builder->CreateNot(A),
                           II->getName());
       Builder->CreateCall(AssumeIntrinsic, Builder->CreateNot(B),
                           II->getName());
       return EraseInstFromFunction(*II);
     }
 
-    // assume( (load addr) != null ) -> add 'nonnull' metadata to load
-    // (if assume is valid at the load)
     if (ICmpInst* ICmp = dyn_cast<ICmpInst>(IIOperand)) {
       Value *LHS = ICmp->getOperand(0);
       Value *RHS = ICmp->getOperand(1);
       if (ICmpInst::ICMP_NE == ICmp->getPredicate() &&
-          isa<LoadInst>(LHS) &&
           isa<Constant>(RHS) &&
           RHS->getType()->isPointerTy() &&
           cast<Constant>(RHS)->isNullValue()) {
-        LoadInst* LI = cast<LoadInst>(LHS);
+        // assume( (load addr) != null ) -> add 'nonnull' metadata to load
+        // (if assume is valid at the load)
+        if (LoadInst* LI = dyn_cast<LoadInst>(LHS)) {
           if (isValidAssumeForContext(II, LI, DL, DT)) {
             MDNode *MD = MDNode::get(II->getContext(), None);
             LI->setMetadata(LLVMContext::MD_nonnull, MD);
             return EraseInstFromFunction(*II);
           }
         }
-      // TODO: apply nonnull return attributes to calls and invokes
+        else if (CallInst *I = dyn_cast<CallInst>(LHS)) {
+          // assume( (call|invoke) != null ) -> add 'nonnull' return attribute
+          if (isValidAssumeForContext(II, I, DL, DT))
+            I->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
+        } else if (InvokeInst *I = dyn_cast<InvokeInst>(LHS))
+          if (isValidAssumeForContext(II, I, DL, DT))
+            I->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
+      }
       // TODO: apply range metadata for range check patterns?
     }
     // If there is a dominating assume with the same condition as this one,
     // then this one is redundant, and should be removed.
     APInt KnownZero(1, 0), KnownOne(1, 0);
     computeKnownBits(IIOperand, KnownZero, KnownOne, 0, II);
     if (KnownOne.isAllOnesValue())
       return EraseInstFromFunction(*II);
case Intrinsic::experimental_gc_relocate: {
     // collector this property does not hold for.
     if (isa<ConstantPointerNull>(DerivedPtr))
       return ReplaceInstUsesWith(*II, DerivedPtr);
 
     // isKnownNonNull -> nonnull attribute
     if (isKnownNonNull(DerivedPtr))
       II->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
 
-    // TODO: dereferenceable -> deref attribute
+    // isDereferenceablePointer -> deref attribute
+    if (DerivedPtr->isDereferenceablePointer())
+      II->addAttribute(AttributeSet::ReturnIndex, Attribute::Dereferenceable);
 
     // TODO: bitcast(relocate(p)) -> relocate(bitcast(p))
     // Canonicalize on the type from the uses to the defs
     
     // TODO: relocate((gep p, C, C2, ...)) -> gep(relocate(p), C, C2, ...)
   }
   }