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

1138

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

1084

Line too long?

lib/Transforms/InstCombine/InstCombineCalls.cpp

if (ICmpInst* ICmp = dyn_cast<ICmpInst>(IIOperand)) {
       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);
         if (isValidAssumeForContext(II, LI, DL, DT)) {
+          // assume( load (call|invoke) != null ) -> add 'nonnull' return attribute
+          Value *LIOperand = LI->getOperand(0);
+          if (CallInst *I = dyn_cast<CallInst>(LIOperand))
+            I->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
+          else if (InvokeInst *I = dyn_cast<InvokeInst>(LIOperand))
+            I->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
+
           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
       // 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);
if (isa<ConstantPointerNull>(DerivedPtr))
       return ReplaceInstUsesWith(*II, DerivedPtr);
 
     // isKnownNonNull -> nonnull attribute
     if (isKnownNonNull(DerivedPtr))
       II->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
 
     // TODO: dereferenceable -> deref attribute
 
     // 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, ...)
   }
   }
 
   return visitCallSite(II);
 }

test/Transforms/InstCombine/assume.ll

entry:
   %rval = icmp eq i32* %load, null
   ret i1 %rval
 
 ; CHECK-LABEL: @nonnull4
 ; CHECK-NOT: !nonnull
 ; CHECK: call void @llvm.assume
 }
 
+declare i32** @id(i32** %a)
 
+; Check that nonnull return attribute is applied to call
+define i1 @nonnull5(i32** %a) {
+entry:
+  %idr = call i32** @id(i32** %a)
+  %load = load i32** %idr
+  %cmp = icmp ne i32* %load, null
+  tail call void @llvm.assume(i1 %cmp)
+  %rval = icmp eq i32* %load, null
+  ret i1 %rval
+
+; CHECK-LABEL: @nonnull5
+; CHECK: call nonnull
+; CHECK-NOT: call void @llvm.assume
+; CHECK: ret i1 false
+}
+
+declare i32 @__personality0(...)
 
+; Check that nonnull return attribute is applied to invoke
+define i1 @nonnull6(i32** %a) {
+entry:
+  %idr = invoke i32** @id(i32** %a) to label %norm unwind label %lpad
+norm:
+  %load = load i32** %idr
+  %cmp = icmp ne i32* %load, null
+  tail call void @llvm.assume(i1 %cmp)
+  %rval = icmp eq i32* %load, null
+  ret i1 %rval
+lpad:
+  %res = landingpad { i8*, i32 } personality i32 (...)* @__personality0 cleanup
+  resume { i8*, i32 } undef
+
+; CHECK-LABEL: @nonnull6
+; CHECK: invoke nonnull
+; CHECK-NOT: call void @llvm.assume
+; CHECK: ret i1 false
+}
 
 attributes #0 = { nounwind uwtable }
 attributes #1 = { nounwind }