rjmccall added inline comments.
================
Comment at: lib/CodeGen/CGStmt.cpp:525
@@ +524,3 @@
+void CodeGenFunction::LexicalNoAliasInfo::addNoAliasMD() {
+ if (MemoryInsts.empty() || NoAliasScopes.empty())
+ return;
----------------
It's much more likely that NoAliasScopes will be empty than that MemoryInsts
will be empty. You should probably fast-path using that, or better yet, with
the RecordMemoryInsts bit.
================
Comment at: lib/CodeGen/CGStmt.cpp:537
@@ +536,3 @@
+ llvm::LLVMContext::MD_noalias),
+ NewScopeList));
+
----------------
hfinkel wrote:
> rjmccall wrote:
> > This is a very strange representation. Every memory operation in the
> > lexical block is annotated with a list of all of the scopes that were
> > entered within the block, even if they were entered after the operation.
> > But for some reason, not with nested scopes?
> >
> > What's the right patch for me to read about this representation?
> Perhaps unfortunately, this is an artifact of the way that restrict is
> defined in C. It applies to all accesses in the block in which the variable
> is declared, even those before the declaration of the restrict-qualified
> local itself.
>
> It should work with nested scopes, in the sense that we add these things as
> we complete each scope. So we add things to the inner scope, and then when we
> complete the outer scope, we go back over the instructions (including those
> in the inner scope because the scope recording recurses up the scope
> hierarchy), and adds the outer scopes - it concatenates them to any added by
> the inner (nested) scopes.
>
> The noalias intrinsic's LangRef updates are in D9375.
Ah, I see the recursion now. Please add a comment explaining that expectation
here.
================
Comment at: lib/CodeGen/CodeGenFunction.cpp:1900
@@ +1899,3 @@
+
+ if (I->mayReadOrWriteMemory())
+ recordMemoryInstruction(I);
----------------
Is it intentional that this includes calls and invokes? If so, please leave a
comment describing which instructions we want to apply this to and why.
In general, this entire patch is really light on comments.
================
Comment at: lib/CodeGen/CodeGenFunction.h:541
@@ +540,3 @@
+
+ LexicalNoAliasInfo(bool RMI = false) : RecordMemoryInsts(RMI) {}
+
----------------
Why this is defaultable?
https://reviews.llvm.org/D9403
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