[ConstantFolding] Support ptrtoadd in IsConstantOffsetFromGlobal()

Handle ptrtoaddr the same way as ptrtoint. This code is already
working on the index size (= address size) of the pointer only.

Author: nikic

llvm/lib/Analysis/ConstantFolding.cpp

@@ -329,6 +329,7 @@ bool llvm::IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
 
   // Look through ptr->int and ptr->ptr casts.
   if (CE->getOpcode() == Instruction::PtrToInt ||
+      CE->getOpcode() == Instruction::PtrToAddr ||
       CE->getOpcode() == Instruction::BitCast)
     return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, DL,
                                       DSOEquiv);

llvm/test/Transforms/InstCombine/ptrtoaddr.ll

@@ -109,3 +109,24 @@ define ptr @inttoptr_of_ptrtoaddr() {
 ;
   ret ptr inttoptr (i64 ptrtoaddr (ptr @g to i64) to ptr)
 }
+
+define i64 @ptrtoaddr_sub_consts_unrelated() {
+; CHECK-LABEL: define i64 @ptrtoaddr_sub_consts_unrelated() {
+; CHECK-NEXT:    ret i64 sub (i64 ptrtoaddr (ptr @g to i64), i64 ptrtoaddr (ptr @g2 to i64))
+;
+  ret i64 sub (i64 ptrtoaddr (ptr @g to i64), i64 ptrtoaddr (ptr @g2 to i64))
+}
+
+define i64 @ptrtoaddr_sub_consts_offset() {
+; CHECK-LABEL: define i64 @ptrtoaddr_sub_consts_offset() {
+; CHECK-NEXT:    ret i64 42
+;
+  ret i64 sub (i64 ptrtoaddr (ptr getelementptr (i8, ptr @g, i64 42) to i64), i64 ptrtoaddr (ptr @g to i64))
+}
+
+define i32 @ptrtoaddr_sub_consts_offset_addrsize() {
+; CHECK-LABEL: define i32 @ptrtoaddr_sub_consts_offset_addrsize() {
+; CHECK-NEXT:    ret i32 42
+;
+  ret i32 sub (i32 ptrtoaddr (ptr addrspace(1) getelementptr (i8, ptr addrspace(1) @g.as1, i32 42) to i32), i32 ptrtoaddr (ptr addrspace(1) @g.as1 to i32))
+}