[InstSimplify] Support ptrtoaddr in simplifyCastInst()

Handle ptrtoaddr the same way as ptrtoint. The fold already only
operates on the index/address bits.

Author: nikic

llvm/lib/Analysis/InstructionSimplify.cpp

@@ -5440,9 +5440,10 @@ static Value *simplifyCastInst(unsigned CastOpc, Value *Op, Type *Ty,
 
   // ptrtoint (ptradd (Ptr, X - ptrtoint(Ptr))) -> X
   Value *Ptr, *X;
-  if (CastOpc == Instruction::PtrToInt &&
-      match(Op, m_PtrAdd(m_Value(Ptr),
-                         m_Sub(m_Value(X), m_PtrToInt(m_Deferred(Ptr))))) &&
+  if ((CastOpc == Instruction::PtrToInt || CastOpc == Instruction::PtrToAddr) &&
+      match(Op,
+            m_PtrAdd(m_Value(Ptr),
+                     m_Sub(m_Value(X), m_PtrToIntOrAddr(m_Deferred(Ptr))))) &&
       X->getType() == Ty && Ty == Q.DL.getIndexType(Ptr->getType()))
     return X;
 

llvm/test/Transforms/InstCombine/ptrtoaddr.ll

@@ -161,3 +161,27 @@ define i32 @ptrtoaddr_sub_known_offset_addrsize(ptr addrspace(1) %p) {
   %sub = sub i32 %p2.addr, %p.addr
   ret i32 %sub
 }
+
+define i64 @ptrtoaddr_of_ptradd_of_sub(i64 %x, ptr %p) {
+; CHECK-LABEL: define i64 @ptrtoaddr_of_ptradd_of_sub(
+; CHECK-SAME: i64 [[X:%.*]], ptr [[P:%.*]]) {
+; CHECK-NEXT:    ret i64 [[X]]
+;
+  %p.addr = ptrtoaddr ptr %p to i64
+  %sub = sub i64 %x, %p.addr
+  %ptradd = getelementptr i8, ptr %p, i64 %sub
+  %ptradd.addr = ptrtoaddr ptr %ptradd to i64
+  ret i64 %ptradd.addr
+}
+
+define i32 @ptrtoaddr_of_ptradd_of_sub_addrsize(i32 %x, ptr addrspace(1) %p) {
+; CHECK-LABEL: define i32 @ptrtoaddr_of_ptradd_of_sub_addrsize(
+; CHECK-SAME: i32 [[X:%.*]], ptr addrspace(1) [[P:%.*]]) {
+; CHECK-NEXT:    ret i32 [[X]]
+;
+  %p.addr = ptrtoaddr ptr addrspace(1) %p to i32
+  %sub = sub i32 %x, %p.addr
+  %ptradd = getelementptr i8, ptr addrspace(1) %p, i32 %sub
+  %ptradd.addr = ptrtoaddr ptr addrspace(1) %ptradd to i32
+  ret i32 %ptradd.addr
+}