[llvm] r350456 - [Inliner] Optimize shouldBeDeferred
Easwaran Raman via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 9 11:34:50 PST 2019
r350751 adds an assert that the threshold cannot be negative. With this
change, the commit description no longer applies.
On Sun, Jan 6, 2019 at 9:56 PM David Blaikie <dblaikie at gmail.com> wrote:
> Could you add a test case for the negative cost situation you mentioned in
> the commit description?
>
> On Sat, Jan 5, 2019 at 1:30 PM Easwaran Raman via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: eraman
>> Date: Fri Jan 4 18:26:29 2019
>> New Revision: 350456
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=350456&view=rev
>> Log:
>> [Inliner] Optimize shouldBeDeferred
>>
>> This has some minor optimizations to shouldBeDeferred. This is not
>> strictly NFC because the early exit inside the loop assumes
>> TotalSecondaryCost is monotonically non-decreasing, which is not true if
>> the threshold used by CostAnalyzer is negative. AFAICT the thresholds do
>> not go below 0 for the default values of the various options we use.
>>
>> Modified:
>> llvm/trunk/lib/Transforms/IPO/Inliner.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/IPO/Inliner.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/Inliner.cpp?rev=350456&r1=350455&r2=350456&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/IPO/Inliner.cpp (original)
>> +++ llvm/trunk/lib/Transforms/IPO/Inliner.cpp Fri Jan 4 18:26:29 2019
>> @@ -311,6 +311,11 @@ shouldBeDeferred(Function *Caller, CallS
>> // For now we only handle local or inline functions.
>> if (!Caller->hasLocalLinkage() && !Caller->hasLinkOnceODRLinkage())
>> return false;
>> + // If the cost of inlining CS is non-positive, it is not going to
>> prevent the
>> + // caller from being inlined into its callers and hence we don't need
>> to
>> + // defer.
>> + if (IC.getCost() <= 0)
>> + return false;
>> // Try to detect the case where the current inlining candidate caller
>> (call
>> // it B) is a static or linkonce-ODR function and is an inlining
>> candidate
>> // elsewhere, and the current candidate callee (call it C) is large
>> enough
>> @@ -330,25 +335,31 @@ shouldBeDeferred(Function *Caller, CallS
>> TotalSecondaryCost = 0;
>> // The candidate cost to be imposed upon the current function.
>> int CandidateCost = IC.getCost() - 1;
>> - // This bool tracks what happens if we do NOT inline C into B.
>> - bool callerWillBeRemoved = Caller->hasLocalLinkage();
>> + // If the caller has local linkage and can be inlined to all its
>> callers, we
>> + // can apply a huge negative bonus to TotalSecondaryCost.
>> + bool ApplyLastCallBonus = Caller->hasLocalLinkage() &&
>> !Caller->hasOneUse();
>> // This bool tracks what happens if we DO inline C into B.
>> bool inliningPreventsSomeOuterInline = false;
>> for (User *U : Caller->users()) {
>> + // If the caller will not be removed (either because it does not
>> have a
>> + // local linkage or because the LastCallToStaticBonus has been
>> already
>> + // applied), then we can exit the loop early.
>> + if (!ApplyLastCallBonus && TotalSecondaryCost >= IC.getCost())
>> + return false;
>> CallSite CS2(U);
>>
>> // If this isn't a call to Caller (it could be some other sort
>> // of reference) skip it. Such references will prevent the caller
>> // from being removed.
>> if (!CS2 || CS2.getCalledFunction() != Caller) {
>> - callerWillBeRemoved = false;
>> + ApplyLastCallBonus = false;
>> continue;
>> }
>>
>> InlineCost IC2 = GetInlineCost(CS2);
>> ++NumCallerCallersAnalyzed;
>> if (!IC2) {
>> - callerWillBeRemoved = false;
>> + ApplyLastCallBonus = false;
>> continue;
>> }
>> if (IC2.isAlways())
>> @@ -366,7 +377,7 @@ shouldBeDeferred(Function *Caller, CallS
>> // one is set very low by getInlineCost, in anticipation that Caller
>> will
>> // be removed entirely. We did not account for this above unless there
>> // is only one caller of Caller.
>> - if (callerWillBeRemoved && !Caller->hasOneUse())
>> + if (ApplyLastCallBonus)
>> TotalSecondaryCost -= InlineConstants::LastCallToStaticBonus;
>>
>> if (inliningPreventsSomeOuterInline && TotalSecondaryCost <
>> IC.getCost())
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190109/131bf50d/attachment.html>
More information about the llvm-commits
mailing list