llvm dev - Jan 2014 - [LLVMdev] Inlining native functions during JIT compilation

Let's say I'm using LLVM to JIT compile a function. Inside that function
I
make a call to a runtime method in a currently loaded library. Is there any
way to get LLVM to inline that function call?

As an example, let's say my jitted function calls memcpy, can I get
memcpy's body inlined somehow? Or can that only be done via lto and aot
compilation?

Thanks,

Timothy Baldridge
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llvm is capable of inlining some of the basic functions like that during
some of the optimization passes. How are you compiling?

On Mon Jan 06 2014 at 9:49:04 AM, Timothy Baldridge <tbaldridge at
gmail.com>
wrote:
> Let's say I'm using LLVM to JIT compile a function. Inside that
function I
> make a call to a runtime method in a currently loaded library. Is there any
> way to get LLVM to inline that function call?
>
> As an example, let's say my jitted function calls memcpy, can I get
> memcpy's body inlined somehow? Or can that only be done via lto and aot
> compilation?
>
> Thanks,
>
> Timothy Baldridge
>
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As long as the JIT knows about the IR for the functions, you should be 
able to use the standard inlining passes.  For standard c routines 
(memcpy,etc..) this knowledge is built in.  For language specific 
routines, you'll have to provide the IR.

Philip

On 1/6/14 9:46 AM, Timothy Baldridge wrote:
> Let's say I'm using LLVM to JIT compile a function. Inside that 
> function I make a call to a runtime method in a currently loaded 
> library. Is there any way to get LLVM to inline that function call?
>
> As an example, let's say my jitted function calls memcpy, can I get 
> memcpy's body inlined somehow? Or can that only be done via lto and 
> aot compilation?
>
> Thanks,
>
> Timothy Baldridge
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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If all your IR is in a single module, and you're willing to reoptimize the
entire module every time you want to do inlining, you can use the existing
machinery pretty easily.

But unless those are both true, the situation is more complicated: my
understanding is the inlining machinery (at least for non-builtins, not
sure how those work) assumes that 1) you're inlining functions from the
same module, and 2) you're optimizing an entire module at a time.  I ended
up writing a custom inlining FunctionPass: I initialize an
InlineCostAnalysis object (which ends up being quite hacky since it expects
to be part of a passmanager even though that's not what we want here), use
that to determine when to inline, call llvm::InlineFunction() when it says
I should, and then use a custom ValueMaterializer to remap references from
objects in the other module (ex global variables, function declarations,
etc) to the correct references in the current module.


On Mon, Jan 6, 2014 at 9:46 AM, Timothy Baldridge <tbaldridge at
gmail.com>wrote:
> Let's say I'm using LLVM to JIT compile a function. Inside that
function I
> make a call to a runtime method in a currently loaded library. Is there any
> way to get LLVM to inline that function call?
>
> As an example, let's say my jitted function calls memcpy, can I get
> memcpy's body inlined somehow? Or can that only be done via lto and aot
> compilation?
>
> Thanks,
>
> Timothy Baldridge
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
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