[PATCH] D25927: [cfi] Implement cfi-icall using inline assembly.

[Eric Christopher via llvm-commits]

On Wed, Oct 26, 2016 at 5:12 PM Peter Collingbourne <peter at pcc.me.uk> wrote:

> pcc added inline comments.
>
>
> ================
> Comment at: lib/Transforms/IPO/LowerTypeTests.cpp:669
> +  if (!Dest->hasLocalLinkage())
> +    OS << ".globl " << Dest->getName() << "\n";
> +  OS << ".type " << Dest->getName() << ", function\n";
> ----------------
> eugenis wrote:
> > eugenis wrote:
> > > pcc wrote:
> > > > I wonder whether we want to escape these names? This appears to be
> the escaping we'd need to use:
> > > > http://llvm-cs.pcc.me.uk/lib/MC/MCSymbol.cpp#53
> > > >
> > > > Maybe it's not necessary though since we pretty much expect all
> names we see to satisfy `MCAsmInfo::isValidUnquotedName`.
> > > Looks like we should escape the names.
> > > It's easy to call a function "\n" with __asm__ in the declaration, and
> that breaks the jumptable code.
> > >
> > It appears that neither llvm-mc nor gnu as support quoted identifier
> properly.
> > Gnu as allows  a quoted string in, for example, .globl directive.
> Llvm-mc does too, but it forgets to unescape it, so, say, "\n" turns into a
> 2-character string when saves as textual asm and read back.
> >
> > Neither support quoted strings in expressions we need to declare
> aliases, like
> >   "\n" = .jumptable + 4.
> >
> > I think I'll just make it a fatal error to apply cfi-icall to any name
> that requires escaping.
> >
> Makes sense, I suppose. Though I think you'll also need to apply IR
> mangling (`Mangler::getNameWithPrefix`).
>
>
This set of APIs is pretty bad. See my recent patches to try to unify it.
I'd appreciate trying to use TLOF->getNameWithPrefix if you can rather than
calling into the mangler specifically.


>
> ================
> Comment at: lib/Transforms/IPO/LowerTypeTests.cpp:693
>
> +static bool isValidUnquotedName(StringRef Name) {
> +  if (Name.empty())
> ----------------
> Maybe `isValidAsmUnquotedName` or something?
>
>
> ================
> Comment at: lib/Transforms/IPO/LowerTypeTests.cpp:709
>  /// for the functions, build the bit sets and lower the llvm.type.test
> calls.
> -void LowerTypeTestsModule::buildBitSetsFromFunctionsX86(
> +void LowerTypeTestsModule::buildBitSetsFromFunctionsNative(
>      ArrayRef<Metadata *> TypeIds, ArrayRef<Function *> Functions) {
> ----------------
> This function should have a FIXME to replace the inline asm with some
> better representation.
>
>
> ================
> Comment at: test/Transforms/LowerTypeTests/function.ll:1-4
> +; RUN: opt -S -lowertypetests -mtriple=i686-unknown-linux-gnu < %s |
> FileCheck --check-prefix=X86 %s
> +; RUN: opt -S -lowertypetests -mtriple=x86_64-unknown-linux-gnu < %s |
> FileCheck --check-prefix=X86 %s
> +; RUN: opt -S -lowertypetests -mtriple=arm-unknown-linux-gnu < %s |
> FileCheck --check-prefix=ARM %s
> +; RUN: opt -S -lowertypetests -mtriple=aarch64-unknown-linux-gnu < %s |
> FileCheck --check-prefix=ARM %s
> ----------------
> Maybe use `check-prefixes` here to reduce duplication below?
>
>
> Repository:
>   rL LLVM
>
> https://reviews.llvm.org/D25927
>
>
>
>
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