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The current state of this patch looks good to me, but I do not have
commit rights. Nick, could you take a look and check this in if
you're okay with it?<br>
<br>
Philip<br>
<br>
<div class="moz-cite-prefix">On 05/19/2014 10:53 AM, Luqman Aden
wrote:<br>
</div>
<blockquote
cite="mid:CADRTvEC1B=eST0eVo8YpLAZ6c8Yd+D84f1epSXyB-q1nVBbxnQ@mail.gmail.com"
type="cite">
<div dir="ltr">ping</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Mon, May 12, 2014 at 1:46 PM, Nick
Lewycky <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:nicholas@mxc.ca" target="_blank">nicholas@mxc.ca</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Luqman
Aden wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
ping<br>
</blockquote>
<br>
``nonnull``<br>
This indicates that the parameter or return
pointer is not null.<br>
This is an optimization hint to the code generator
allowing it to possibly<br>
omit some null checks. This is not checked or
enforced and thus the pointer<br>
must be guaranteed by the caller to be non-null.
This parameter may only be<br>
applied to pointer types.<br>
<br>
This is fine as is, but I'd rather you put the correctness
information up front, making it:<br>
<br>
``nonnull``<br>
This indicates that the parameter or return
pointer is not null. This attribute may only be applied to
pointer typed parameters. This is not checked or enforced by
LLVM, the caller must ensure that the pointer passed in is
non-null, or the callee must ensure that the returned
pointer is non-null.<br>
<br>
Something like that.<br>
<br>
In ValueTracking.cpp:<br>
<br>
// Is it marked not null?<br>
if (const Argument *A =
dyn_cast<Argument>(V))<br>
return A->hasNonNullAttr();<br>
<br>
// A byval or inalloca argument is never null.<br>
if (const Argument *A =
dyn_cast<Argument>(V))<br>
return A->hasByValOrInAllocaAttr();<br>
<br>
<br>
Fine as is, but I'd prefer if you'd fold the two
if-statements into one, and get:<br>
<br>
if (const Argument *A = dyn_cast<Argument>(V))<br>
return A->hasByValOrInAllocaAttr() ||
A->hasNonNullAttr();<br>
<br>
It should only matter in unoptimized builds.<br>
<br>
There's more you can do in instcombine, this:<br>
<br>
declare void @callee(i8* nonnull)<br>
define void @test() {<br>
call @callee(i8* null)<br>
ret void<br>
}<br>
<br>
can be optimized away to unreachable. You don't need to
include that in this patch.<br>
<br>
<br>
You need to add your attribute to the commented-out block
inside the definition of LLVMAttribute in
include/llvm-c/Core.h .<br>
<br>
With that done, please submit.<br>
<br>
Nick<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="">
On Tue, Apr 22, 2014 at 1:09 PM, Luqman Aden <<a
moz-do-not-send="true"
href="mailto:me%2Bllvm@luqman.ca" target="_blank">me+llvm@luqman.ca</a><br>
</div>
<div class="">
<mailto:<a moz-do-not-send="true"
href="mailto:me%2Bllvm@luqman.ca" target="_blank">me+llvm@luqman.ca</a>>>
wrote:<br>
<br>
ping<br>
<br>
<br>
On Fri, Apr 18, 2014 at 9:12 PM, Philip Reames<br>
</div>
<div class="">
<<a moz-do-not-send="true"
href="mailto:listmail@philipreames.com"
target="_blank">listmail@philipreames.com</a>
<mailto:<a moz-do-not-send="true"
href="mailto:listmail@philipreames.com"
target="_blank">listmail@philipreames.com</a>>>
wrote:<br>
<br>
Good catch. This is a real corner case in the
attribute<br>
specification. Possibly we should document the
distinction<br>
somewhere?<br>
<br>
Which reminds me, we'll need doc changes
(LangRef) to describe<br>
the new attribute.<br>
<br>
Philip<br>
<br>
<br>
On 04/17/2014 10:43 PM, Hal Finkel wrote:<br>
<br>
----- Original Message -----<br>
<br>
From: "Nick Lewycky" <<a
moz-do-not-send="true" href="mailto:nicholas@mxc.ca"
target="_blank">nicholas@mxc.ca</a><br>
</div>
<mailto:<a moz-do-not-send="true"
href="mailto:nicholas@mxc.ca" target="_blank">nicholas@mxc.ca</a>>><br>
To: reviews+D3389+public+
<a class="moz-txt-link-abbreviated" href="mailto:a85d4f162cd7a6e0@reviews.llvm">a85d4f162cd7a6e0@reviews.llvm</a>.<br>
org<br>
<mailto:<a moz-do-not-send="true"
href="mailto:reviews%252BD3389%252Bpublic%252Ba85d4f162cd7a6e0@reviews.llvm.org"
target="_blank">reviews%2BD3389%2Bpublic%2Ba85d4f162cd7a6e0@reviews.llvm.org</a>><br>
Cc: <a moz-do-not-send="true"
href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">llvm-commits@cs.uiuc.edu</a><br>
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<div>
<div class="h5"><br>
Sent: Thursday, April 17, 2014
10:52:35 PM<br>
Subject: Re: [PATCH] `nonnull`
argument attribute.<br>
<br>
Your change to lib/IR/Value.cpp is
wrong, a nonnull<br>
pointer is not<br>
necessarily dereferenceable.<br>
<br>
%a = inttoptr i32 123456 to i32*<br>
call void @foo(i32* %a nonnull)<br>
<br>
It's nonnull, but not dereferenceable.<br>
<br>
I'll add that we really should have a
dereferenceable<br>
attribute, IMHO, but as Nick said, it
needs to be a separate<br>
from notnull. I think that for
dereferenceable we'll want to<br>
have a more involved discussion because
we'll need to decide<br>
if it affects derived pointers, should it
have a size<br>
parameter, etc.<br>
<br>
-Hal<br>
<br>
Nick<br>
<br>
Luqman Aden wrote:<br>
<br>
Added test.<br>
<br>
<a moz-do-not-send="true"
href="http://reviews.llvm.org/D3389" target="_blank">http://reviews.llvm.org/D3389</a><br>
<br>
CHANGE SINCE LAST DIFF<br>
<a moz-do-not-send="true"
href="http://reviews.llvm.org/D3389" target="_blank">http://reviews.llvm.org/D3389</a>?
vs=8552&id=8553#toc<br>
<<a moz-do-not-send="true"
href="http://reviews.llvm.org/D3389?vs=8552&id=8553#toc"
target="_blank">http://reviews.llvm.org/D3389?vs=8552&id=8553#toc</a>><br>
<br>
Files:<br>
lib/AsmParser/LLToken.h<br>
lib/AsmParser/LLParser.cpp<br>
lib/AsmParser/LLLexer.cpp<br>
lib/Bitcode/Writer/
BitcodeWriter.cpp<br>
lib/Bitcode/Reader/
BitcodeReader.cpp<br>
lib/IR/Function.cpp<br>
lib/IR/Attributes.cpp<br>
lib/Analysis/ValueTracking.cpp<br>
test/Bitcode/attributes.ll<br>
test/Analysis/BasicAA/nonnull. ll<br>
include/llvm/Bitcode/
LLVMBitCodes.h<br>
include/llvm/IR/Attributes.h<br>
include/llvm/IR/Argument.h<br>
<br>
<br>
<br>
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