[llvm] r206429 - Inline a function when the always_inline attribute

[Eric Christopher]

Wait, are we sure this is a good idea then? I'm pretty sure this is
why we'd turned it off in the first place.

Also, what happened to the rest of the discussion?

-eric

On Wed, Apr 16, 2014 at 5:21 PM, Gerolf Hoflehner <ghoflehner at apple.com> wrote:
> Author: ghoflehner
> Date: Wed Apr 16 19:21:52 2014
> New Revision: 206429
>
> URL: http://llvm.org/viewvc/llvm-project?rev=206429&view=rev
> Log:
> Inline a function when the always_inline attribute
> is set even when it contains a indirect branch.
> The attribute overrules correctness concerns
> like the escape of a local block address.
>
> This is for rdar://16501761
>
>
>
> Added:
>     llvm/trunk/test/Transforms/Inline/always-inline-attribute.ll
> Modified:
>     llvm/trunk/lib/Analysis/IPA/InlineCost.cpp
>     llvm/trunk/test/Transforms/Inline/always-inline.ll
>
> Modified: llvm/trunk/lib/Analysis/IPA/InlineCost.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/IPA/InlineCost.cpp?rev=206429&r1=206428&r2=206429&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/IPA/InlineCost.cpp (original)
> +++ llvm/trunk/lib/Analysis/IPA/InlineCost.cpp Wed Apr 16 19:21:52 2014
> @@ -1300,8 +1300,14 @@ bool InlineCostAnalysis::isInlineViable(
>      F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
>                                     Attribute::ReturnsTwice);
>    for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
> -    // Disallow inlining of functions which contain an indirect branch.
> -    if (isa<IndirectBrInst>(BI->getTerminator()))
> +    // Disallow inlining of functions which contain an indirect branch,
> +    // unless the always_inline attribute is set.
> +    // The attribute serves as a assertion that no local address
> +    // like a block label can escpape the function.
> +    // Revisit enabling inlining for functions with indirect branches
> +    // when a more sophisticated espape/points-to analysis becomes available.
> +    if (isa<IndirectBrInst>(BI->getTerminator()) &&
> +        !F.hasFnAttribute(Attribute::AlwaysInline))
>        return false;
>
>      for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
>
> Added: llvm/trunk/test/Transforms/Inline/always-inline-attribute.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/Inline/always-inline-attribute.ll?rev=206429&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/Inline/always-inline-attribute.ll (added)
> +++ llvm/trunk/test/Transforms/Inline/always-inline-attribute.ll Wed Apr 16 19:21:52 2014
> @@ -0,0 +1,26 @@
> +; RUN: opt < %s -O3 -S | FileCheck %s
> + at gv = external global i32
> +
> +define i32 @main() nounwind {
> +; CHECK-NOT: call i32 @foo
> +  %1 = load i32* @gv, align 4
> +  %2 = tail call i32 @foo(i32 %1)
> +  unreachable
> +}
> +
> +define internal i32 @foo(i32) alwaysinline {
> +  br label %2
> +
> +; <label>:2                                       ; preds = %8, %1
> +  %3 = phi i32 [ %0, %1 ], [ %10, %8 ]
> +  %4 = phi i8* [ blockaddress(@foo, %2), %1 ], [ %6, %8 ]
> +  %5 = icmp eq i32 %3, 1
> +  %6 = select i1 %5, i8* blockaddress(@foo, %8), i8* %4
> +  %7 = add nsw i32 %3, -1
> +  br label %8
> +
> +; <label>:8                                       ; preds = %8, %2
> +  %9 = phi i32 [ %7, %2 ], [ %10, %8 ]
> +  %10 = add nsw i32 %9, -1
> +  indirectbr i8* %6, [label %2, label %8]
> +}
>
> 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=206429&r1=206428&r2=206429&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/Inline/always-inline.ll (original)
> +++ llvm/trunk/test/Transforms/Inline/always-inline.ll Wed Apr 16 19:21:52 2014
> @@ -78,7 +78,7 @@ entry:
>    ret i32 %add
>  }
>
> -define i32 @inner5(i8* %addr) alwaysinline {
> +define i32 @inner5(i8* %addr) {
>  entry:
>    indirectbr i8* %addr, [ label %one, label %two ]
>
>
>
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