[PATCH] D125272: [clang] Add -fcheck-new support

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added inline comments.


================
Comment at: clang/test/CodeGenCXX/fcheck-new.cpp:2
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1 -fcheck-new -triple x86_64-linux-gnu -S -disable-O0-optnone \
+// RUN: -emit-llvm -o - %s | opt -S -passes=mem2reg | FileCheck %s
----------------
heatd wrote:
> MaskRay wrote:
> > In this test, if I remove `-fcheck-new` , nothing will change. So this isn't a good test.
> > 
> > I think we need something like:
> > ```
> > struct A { A(); };
> > void *test0() { return A; }
> > ```
> It will change (the attributes of _Znwm).
> 
> From the test (with -fcheck-new):
> ```
> [[CALL:%.*]] = call noalias noundef ptr @_Znwm(i64 noundef 4) #[[ATTR2:[0-9]+]]
> ```
> The same test (but without -fcheck-new, tested locally):
> 
> ```
>   %1 = tail call noalias noundef nonnull dereferenceable(4) ptr @_Znwm(i64 noundef 4) #2
> ```
> 
> As you'll see, the non-fcheck-new has nonnull attached to _Znwm, while -fcheck-new doesn't. This is exactly the behavior we want to test for.
OK, you are right about `nonull`. I think my point still holds as with a constructor the effect will be more visible with a `new.notnull:` basic block.
You may want to add another function to do `A *test1() { return new A; }`

Also, with the simple IR, `opt -S -mem2reg ` is a no-op. You should remove it.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D125272/new/

https://reviews.llvm.org/D125272