[ValueTracking] Look through constant Int2Ptr/Ptr2Int expressions

[jdoerfert]

Summary

This is analogous to the int2ptr/ptr2int instruction handling introduced
in D54956.

[lebedev.ri]

Looks good to me.

llvm/trunk/lib/Analysis/ValueTracking.cpp

 bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q) {
   if (auto *C = dyn_cast<Constant>(V)) {
     if (C->isNullValue())
       return false;
     if (isa<ConstantInt>(C))
       // Must be non-zero due to null test above.
       return true;
 
+    if (auto *CE = dyn_cast<ConstantExpr>(C)) {
+      // See the comment for IntToPtr/PtrToInt instructions below.
+      if (CE->getOpcode() == Instruction::IntToPtr ||
+          CE->getOpcode() == Instruction::PtrToInt)
+        if (Q.DL.getTypeSizeInBits(CE->getOperand(0)->getType()) <=
+            Q.DL.getTypeSizeInBits(CE->getType()))
+          return isKnownNonZero(CE->getOperand(0), Depth, Q);
+    }
+
     // For constant vectors, check that all elements are undefined or known
     // non-zero to determine that the whole vector is known non-zero.
     if (auto *VecTy = dyn_cast<VectorType>(C->getType())) {
       for (unsigned i = 0, e = VecTy->getNumElements(); i != e; ++i) {
         Constant *Elt = C->getAggregateElement(i);
         if (!Elt || Elt->isNullValue())
           return false;
         if (!isa<UndefValue>(Elt) && !isa<ConstantInt>(Elt))

llvm/trunk/test/Transforms/FunctionAttrs/nonnull.ll

 }
 
 ; CHECK: define i32 addrspace(3)* @gep2(
 define i32 addrspace(3)* @gep2(i32 addrspace(3)* %p) {
   %q = getelementptr inbounds i32, i32 addrspace(3)* %p, i32 1
   ret i32 addrspace(3)* %q
 }
 
+; CHECK: define internal nonnull i32* @f2()
+define internal i32* @f2() {
+  ret i32* inttoptr (i64 4 to i32*)
+}
+
+define  i32* @f1() {
+ %c = call i32* @f2()
+  ret i32* %c
+}
+
 attributes #0 = { "null-pointer-is-valid"="true" }