[PATCH]: -fno-inline doesnt prevent inlining

[Reid Kleckner]

I find the LTO argument compellingly in favor of using the NoInline
attribute.

On Tue, Jan 14, 2014 at 3:31 PM, Chandler Carruth <chandlerc at google.com>wrote:

> Are there strong reasons to do this by adding attributes rather than
> changing the optimizer's behavior? I'm uncertain.
>
> On one hand, it would be more efficient in the optimizer to just switch to
> the always-inliner pass.
>
> On the other hand, if we are doing an LTO build, adding attributes ensures
> that even the link-top inline step doesn't inline those functions.
>
> On the other other hand, if we are doing an LTO build, we might want to
> only prevent inlining during the per-TU optimization run, not during the
> LTO optimization run.
>
> Thoughts?
>
>
> On Tue, Jan 14, 2014 at 11:58 AM, Roman Divacky <rdivacky at freebsd.org>wrote:
>
>> Hi,
>>
>> Currently -fno-inline doesnt do much, it just prevents adding InlineHint
>> attributes. This means that we differ from gcc which prevents all
>> functions (except always_inline) from inlining. This simple patch
>> implements that behaviour, is that ok?
>>
>> Index: lib/CodeGen/CodeGenFunction.cpp
>> ===================================================================
>> --- lib/CodeGen/CodeGenFunction.cpp     (revision 199224)
>> +++ lib/CodeGen/CodeGenFunction.cpp     (working copy)
>> @@ -510,7 +510,7 @@
>>
>>    // Pass inline keyword to optimizer if it appears explicitly on any
>>    // declaration.
>> -  if (!CGM.getCodeGenOpts().NoInline)
>> +  if (!CGM.getCodeGenOpts().NoInline) {
>>      if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D))
>>        for (FunctionDecl::redecl_iterator RI = FD->redecls_begin(),
>>               RE = FD->redecls_end(); RI != RE; ++RI)
>> @@ -518,6 +518,10 @@
>>            Fn->addFnAttr(llvm::Attribute::InlineHint);
>>            break;
>>          }
>> +  } else if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D))
>> +    if (!FD->hasAttr<AlwaysInlineAttr>() &&
>> +        !FD->hasAttr<ForceInlineAttr>())
>> +      Fn->addFnAttr(llvm::Attribute::NoInline);
>>
>>    if (getLangOpts().OpenCL) {
>>      // Add metadata for a kernel function.
>> Index: test/CodeGen/noinline.c
>> ===================================================================
>> --- test/CodeGen/noinline.c     (revision 199224)
>> +++ test/CodeGen/noinline.c     (working copy)
>> @@ -7,6 +7,7 @@
>>
>>  volatile int *pa = (int*) 0x1000;
>>  void foo() {
>> +// NOINLINE: Function Attrs: noinline
>>  // NOINLINE: @foo
>>  // NOINLINE: dont_inline_me
>>  // NOINLINE-NOT: inlinehint
>>
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>
>
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