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[CSSPGO] Honor preinliner decision for ThinLTO importing 

When pre-inliner decision is used for CSSPGO, we should take that into account for ThinLTO importing as well, so post-link sample loader inliner can favor that decision. This is handled by a small tweak in this patch. It also includes a change to transfer preinliner decision when merging context.

Differential Revision: https://reviews.llvm.org/D109088
This commit is contained in:
Wenlei He 2021-09-01 13:47:19 -07:00
parent 2cfda6a691
commit 054487c5b2
3 changed files with 23 additions and 6 deletions
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2
llvm/lib/Transforms/IPO/SampleContextTracker.cpp
View File

@ -545,6 +545,8 @@ void SampleContextTracker::mergeContextNode(ContextTrieNode &FromNode,
ToSamples->merge(*FromSamples);
ToSamples->getContext().setState(SyntheticContext);
FromSamples->getContext().setState(MergedContext);
if (FromSamples->getContext().hasAttribute(ContextShouldBeInlined))
ToSamples->getContext().setAttribute(ContextShouldBeInlined);
} else if (FromSamples) {
// Transfer FromSamples from FromNode to ToNode
ToNode.setFunctionSamples(FromSamples);

22
llvm/lib/Transforms/IPO/SampleProfile.cpp
View File

@ -982,7 +982,14 @@ void SampleProfileLoader::findExternalInlineCandidate(
// For CSSPGO profile, retrieve candidate profile by walking over the
// trie built for context profile. Note that also take call targets
// even if callee doesn't have a corresponding context profile.
if (!CalleeSample || CalleeSample->getEntrySamples() < Threshold)
if (!CalleeSample)
continue;
// If pre-inliner decision is used, honor that for importing as well.
bool PreInline =
UsePreInlinerDecision &&
CalleeSample->getContext().hasAttribute(ContextShouldBeInlined);
if (!PreInline && CalleeSample->getEntrySamples() < Threshold)
continue;
StringRef Name = CalleeSample->getFuncName();
@ -1306,10 +1313,15 @@ SampleProfileLoader::shouldInlineCandidate(InlineCandidate &Candidate) {
// we replay that inline decision under `sample-profile-use-preinliner`.
// Note that we don't need to handle negative decision from preinliner as
// context profile for not inlined calls are merged by preinliner already.
if (UsePreInlinerDecision &&
Candidate.CalleeSamples->getContext().hasAttribute(
ContextShouldBeInlined))
return InlineCost::getAlways("preinliner");
if (UsePreInlinerDecision && Candidate.CalleeSamples) {
// Once two node are merged due to promotion, we're losing some context
// so the original context-sensitive preinliner decision should be ignored
// for SyntheticContext.
SampleContext &Context = Candidate.CalleeSamples->getContext();
if (!Context.hasState(SyntheticContext) &&
Context.hasAttribute(ContextShouldBeInlined))
return InlineCost::getAlways("preinliner");
}
// For old FDO inliner, we inline the call site as long as cost is not
// "Never". The cost-benefit check is done earlier.

5
llvm/test/Transforms/SampleProfile/csspgo-use-preinliner.ll
View File

@ -8,9 +8,12 @@
; DEFAULT-NOT: inlined into
; PREINLINE-NOT: inlined into
; `[main:3 @ _Z5funcAi]` does not have preinline decision, so it's up for loader inliner to decided.
; PREINLINE: '_Z5funcAi' inlined into 'main'
; `[main:3 @ _Z5funcAi:1 @ _Z8funcLeafi]` is inlined according to preinline decision.
; PREINLINE: '_Z8funcLeafi' inlined into 'main'
; PREINLINE: '_Z8funcLeafi' inlined into '_Z5funcBi'
; Even though `[main:3.1 @ _Z5funcBi]` context is marked should inline, `_Z5funcBi` is a noinline function, so we honor that and don't inline.
; When _Z5funcBi is promoted to be top level context-less profile, `[_Z5funcBi:1 @ _Z8funcLeafi]` becomes synthetic context, so preinline decision is ignored and we don't inline `_Z8funcLeafi`.
; PREINLINE-NOT: inlined into
@factor = dso_local global i32 3, align 4, !dbg !0