[llvm-dev] [RFC] Enable Partial Inliner by default (original) (raw)
Graham Yiu via llvm-dev llvm-dev at lists.llvm.org
Tue Nov 7 08:19:35 PST 2017
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Hi Evgeny,
When you think the experiments on armv7m and armv6m targets will be complete? We're looking to turn this on sooner rather than later, if there aren't objections from folks running on other platforms.
Cheers,
Graham Yiu LLVM Compiler Development IBM Toronto Software Lab Office: (905) 413-4077 C2-707/8200/Markham Email: gyiu at ca.ibm.com
From: Graham Yiu/Toronto/IBM To: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com> Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>, "llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>, Tobias Grosser <tobias.grosser at inf.ethz.ch> Date: 11/03/2017 12:40 PM Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default
Hi Evgeny,
Yes, please do. It was our hope that folks would verify the impact of the partial inliner on the platforms they're currently working on.
Cheers,
Graham Yiu LLVM Compiler Development IBM Toronto Software Lab Office: (905) 413-4077 C2-707/8200/Markham Email: gyiu at ca.ibm.com
From: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com> To: Tobias Grosser <tobias.grosser at inf.ethz.ch>, Graham Yiu <gyiu at ca.ibm.com> Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>, "llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com> Date: 11/03/2017 12:18 PM Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default
Hi,
We'd like to check impact on armv7m and armv6m targets, especially code size. We have not tried the partial inliner on them.
Could a decision to turn it on by default wait for results?
Thanks,
Evgeny Astigeevich
The Arm Compiler Optimization team
-----Original Message-----
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Tobias Grosser via llvm-dev <llvm-dev at lists.llvm.org>
Reply-To: Tobias Grosser <tobias.grosser at inf.ethz.ch>
Date: Thursday, 2 November 2017 at 23:32
To: Graham Yiu <gyiu at ca.ibm.com>, "llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default
Hi Graham,
I think this is a good idea. It is also useful for libquantum, where
together with some other changes, it enables Polly to perform libfusion.
The ARM people also played with the partial inliner and might have
feedback.
Best,
Tobias
On Thu, Nov 2, 2017, at 23:05, Graham Yiu via llvm-dev wrote:
Forgot to add that all experiments were done with '-O3 -m64
-fexperimental-new-pass-manager'.
Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077 C2-707/8200/Markham
Email: gyiu at ca.ibm.com
From: Graham Yiu/Toronto/IBM
Date: 11/02/2017 05:26 PM
Subject: [RFC] Enable Partial Inliner by default
Hello,
I'd like to propose turning on the partial inliner
(-enable-partial-inlining) by default.
We've seen small gains on SPEC2006/2017 runtimes as well as lnt
compile-times with a 2nd stage bootstrap of LLVM. We also saw positive
gains on our internal workloads.
-------------------------------------
Brief description of Partial Inlining
-------------------------------------
A pass in opt that runs after the normal inlining pass. Looks for
branches
to a return block in the entry and immediate successor blocks of a
function. If found, it outlines the rest of the function using the
CodeExtractor. It then attempts to inline the leftover entry block (and
possibly one or more of its successors) to all its callers. This
effectively peels the early return block(s) into the caller, which could
be
executed without incurring the call overhead of the function just to
return
immediately. Inlining and call overhead cost, as well as branch
probabilities of the return block(s) are taken into account before
inlining
is done. If inlining is not successful, then the changes are discarded.
eg.
void foo() {
bar();
// rest of the code in foo
}
void bar() {
if (X)
return;
// rest of code (to be outlined)
}
After Partial Inlining:
void foo() {
if (!X)
bar.outlined();
// rest of the code in foo
}
void bar.outlined() {
// rest of the code in bar
}
Here are the numbers on a Power8 PPCLE running Ubuntu 15.04 in ST-mode
----------------------------------------------
Runtime performance (speed)
----------------------------------------------
Workload Improvement
-------- -----------
SPEC2006(C/C++) 0.06% (geomean)
SPEC2017(C/C++) 0.10% (geomean)
----------------------------------------------
Compile time performance for Bootstrapped LLVM
----------------------------------------------
Workload Improvement
-------- -----------
SPEC2006(C/C++) 0.41% (cumulative)
SPEC2017(C/C++) -0.16% (cumulative)
lnt 0.61% (geomean)
----------------------------------------------
Compile time performance
----------------------------------------------
Workload Increase
-------- --------
SPEC2006(C/C++) 1.31% (cumulative)
SPEC2017(C/C++) 0.25% (cumulative)
----------------------------------------------
Code size
----------------------------------------------
Workload Increase
-------- --------
SPEC2006(C/C++) 3.90% (geomean)
SPEC2017(C/C++) 1.05% (geomean)
NOTE1: Code size increase in SPEC2006 was mainly attributed to benchmark
"astar", which increased by 86%. Removing this outlier, we get a more
reasonable increase of 0.58%.
NOTE2: There is a patch up for review on Phabricator to enhance the
partial
inliner with the presence of profiling information (
Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077 C2-707/8200/Markham
Email: gyiu at ca.ibm.com
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