[ValueTracking] Look through constant Int2Ptr/Ptr2Int expressions

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

Reviewers: fhahn, efriedma, spatel, nlopes, sanjoy, lebedev.ri

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64708

llvm-svn: 366036

llvm/lib/Analysis/ValueTracking.cpp

@@ -1998,6 +1998,15 @@ bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q) {
       // 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())) {

llvm/test/Transforms/FunctionAttrs/nonnull.ll

@@ -237,4 +237,14 @@ define i32 addrspace(3)* @gep2(i32 addrspace(3)* %p) {
   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" }