[llvm] r179071 - c++ new operators are not malloc-like functions because they do not return uninitialized memory.

[Nick Lewycky]

On 04/08/2013 04:40 PM, Nadav Rotem wrote:
> Author: nadav
> Date: Mon Apr  8 18:40:47 2013
> New Revision: 179071
>
> URL: http://llvm.org/viewvc/llvm-project?rev=179071&view=rev
> Log:
> c++ new operators are not malloc-like functions because they do not return uninitialized memory.
> Users may overide new-operators and implement any function that they like.

Please revert. Technically true, but this was discussed in advance: if 
people want non-standard new/new[] then they need to specify 
-fno-builtin just as they need for non-standard malloc (even though 
replacing new/new[] is part of the language spec and replacing malloc 
isn't (well, except that it also is but you have to replace the rest of 
the standard library with it.))

Nick

> Added:
>      llvm/trunk/test/Transforms/GVN/newoperator.ll
> Modified:
>      llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
>      llvm/trunk/test/Transforms/InstCombine/invoke.ll
>      llvm/trunk/test/Transforms/InstCombine/objsize-64.ll
>
> Modified: llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemoryBuiltins.cpp?rev=179071&r1=179070&r2=179071&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/MemoryBuiltins.cpp (original)
> +++ llvm/trunk/lib/Analysis/MemoryBuiltins.cpp Mon Apr  8 18:40:47 2013
> @@ -52,14 +52,6 @@ struct AllocFnsTy {
>   static const AllocFnsTy AllocationFnData[] = {
>     {LibFunc::malloc,              MallocLike,  1, 0,  -1},
>     {LibFunc::valloc,              MallocLike,  1, 0,  -1},
> -  {LibFunc::Znwj,                MallocLike,  1, 0,  -1}, // new(unsigned int)
> -  {LibFunc::ZnwjRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned int, nothrow)
> -  {LibFunc::Znwm,                MallocLike,  1, 0,  -1}, // new(unsigned long)
> -  {LibFunc::ZnwmRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned long, nothrow)
> -  {LibFunc::Znaj,                MallocLike,  1, 0,  -1}, // new[](unsigned int)
> -  {LibFunc::ZnajRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned int, nothrow)
> -  {LibFunc::Znam,                MallocLike,  1, 0,  -1}, // new[](unsigned long)
> -  {LibFunc::ZnamRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned long, nothrow)
>     {LibFunc::posix_memalign,      MallocLike,  3, 2,  -1},
>     {LibFunc::calloc,              CallocLike,  2, 0,   1},
>     {LibFunc::realloc,             ReallocLike, 2, 1,  -1},
>
> Added: llvm/trunk/test/Transforms/GVN/newoperator.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/newoperator.ll?rev=179071&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/GVN/newoperator.ll (added)
> +++ llvm/trunk/test/Transforms/GVN/newoperator.ll Mon Apr  8 18:40:47 2013
> @@ -0,0 +1,20 @@
> +; RUN: opt<  %s -basicaa -gvn -S | FileCheck %s
> +
> +; We can't remove the load because new operators are overideable and can return non-undefined memory.
> +;CHECK: main
> +;CHECK: load
> +;CHECK: ret
> +define i32 @main(i32 %argc, i8** nocapture %argv) ssp uwtable {
> +  %1 = tail call noalias i8* @_Znam(i64 800)
> +  %2 = bitcast i8* %1 to i32**
> +  %3 = load i32** %2, align 8, !tbaa !0
> +  %4 = icmp eq i32* %3, null
> +  %5 = zext i1 %4 to i32
> +  ret i32 %5
> +}
> +
> +declare noalias i8* @_Znam(i64)
> +
> +!0 = metadata !{metadata !"any pointer", metadata !1}
> +!1 = metadata !{metadata !"omnipotent char", metadata !2}
> +!2 = metadata !{metadata !"Simple C/C++ TBAA"}
>
> Modified: llvm/trunk/test/Transforms/InstCombine/invoke.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/invoke.ll?rev=179071&r1=179070&r2=179071&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/invoke.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/invoke.ll Mon Apr  8 18:40:47 2013
> @@ -47,19 +47,3 @@ lpad:
>     unreachable
>   }
>
> -; CHECK: @f3
> -define void @f3() nounwind uwtable ssp {
> -; CHECK: invoke void @llvm.donothing()
> -  %call = invoke noalias i8* @_Znwm(i64 13)
> -          to label %invoke.cont unwind label %lpad
> -
> -invoke.cont:
> -  ret void
> -
> -lpad:
> -  %1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
> -          filter [0 x i8*] zeroinitializer
> -  %2 = extractvalue { i8*, i32 } %1, 0
> -  tail call void @__cxa_call_unexpected(i8* %2) noreturn nounwind
> -  unreachable
> -}
>
> Modified: llvm/trunk/test/Transforms/InstCombine/objsize-64.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/objsize-64.ll?rev=179071&r1=179070&r2=179071&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/objsize-64.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/objsize-64.ll Mon Apr  8 18:40:47 2013
> @@ -25,7 +25,7 @@ entry:
>             to label %invoke.cont unwind label %lpad
>
>   invoke.cont:
> -; CHECK: ret i64 13
> +; CHECK: ret i64 %0
>     store i8* %call, i8** %esc
>     %0 = tail call i64 @llvm.objectsize.i64(i8* %call, i1 false)
>     ret i64 %0
>
>
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