[llvm] r305245 - Inliner: Don't remove calls to readnone+nounwind (but not always_inline) functions in the AlwaysInliner

[David Blaikie via llvm-commits]

Hey Chandler - wouldn't mind a touch of post-commit review here (just in
case this wouldn't've otherwise crossed your dashboard).

Specifically this moves the shouldInline call in the non-trivial case to
before the InlineHistory lookup. I'm wondering if that could have a
significant performance impact such that it'd be worth consulting the
InlineHistory before the shouldInline test.

(similarly, I don't have a great sense for whether shouldInline might be
substantially more expensive than 'isInstructionTriviallyDead' in case it'd
be better for those to be in the opposite order)

This is currently the tidiest way to write this - but if those orderings
are likely to be important I'm happy to refactor it to address them.

- Dave

On Mon, Jun 12, 2017 at 4:01 PM David Blaikie via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: dblaikie
> Date: Mon Jun 12 18:01:17 2017
> New Revision: 305245
>
> URL: http://llvm.org/viewvc/llvm-project?rev=305245&view=rev
> Log:
> Inliner: Don't remove calls to readnone+nounwind (but not always_inline)
> functions in the AlwaysInliner
>
> Modified:
>     llvm/trunk/lib/Transforms/IPO/Inliner.cpp
>     llvm/trunk/test/Transforms/Inline/always-inline.ll
>
> Modified: llvm/trunk/lib/Transforms/IPO/Inliner.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/Inliner.cpp?rev=305245&r1=305244&r2=305245&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/IPO/Inliner.cpp (original)
> +++ llvm/trunk/lib/Transforms/IPO/Inliner.cpp Mon Jun 12 18:01:17 2017
> @@ -523,6 +523,16 @@ inlineCallsImpl(CallGraphSCC &SCC, CallG
>        if (!Callee || Callee->isDeclaration())
>          continue;
>
> +      // FIXME for new PM: because of the old PM we currently generate
> ORE and
> +      // in turn BFI on demand.  With the new PM, the ORE dependency
> should
> +      // just become a regular analysis dependency.
> +      OptimizationRemarkEmitter ORE(Caller);
> +
> +      // If the policy determines that we should inline this function,
> +      // delete the call instead.
> +      if (!shouldInline(CS, GetInlineCost, ORE))
> +        continue;
> +
>        // If this call site is dead and it is to a readonly function, we
> should
>        // just delete the call instead of trying to inline it, regardless
> of
>        // size.  This happens because IPSCCP propagates the result out of
> the
> @@ -548,15 +558,6 @@ inlineCallsImpl(CallGraphSCC &SCC, CallG
>          // Get DebugLoc to report. CS will be invalid after Inliner.
>          DebugLoc DLoc = CS.getInstruction()->getDebugLoc();
>          BasicBlock *Block = CS.getParent();
> -        // FIXME for new PM: because of the old PM we currently generate
> ORE and
> -        // in turn BFI on demand.  With the new PM, the ORE dependency
> should
> -        // just become a regular analysis dependency.
> -        OptimizationRemarkEmitter ORE(Caller);
> -
> -        // If the policy determines that we should inline this function,
> -        // try to do so.
> -        if (!shouldInline(CS, GetInlineCost, ORE))
> -          continue;
>
>          // Attempt to inline the function.
>          using namespace ore;
>
> Modified: llvm/trunk/test/Transforms/Inline/always-inline.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/always-inline.ll?rev=305245&r1=305244&r2=305245&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/Inline/always-inline.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/always-inline.ll Mon Jun 12 18:01:17
> 2017
> @@ -305,3 +305,14 @@ entry:
>    ret void
>  ; CHECK: ret void
>  }
> +
> +define void @inner14() readnone nounwind {
> +; CHECK: define void @inner14
> +  ret void
> +}
> +
> +define void @outer14() {
> +; CHECK: call void @inner14
> +  call void @inner14()
> +  ret void
> +}
>
>
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