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[thinlto] Don't decay threshold for hot callsites 

Summary:
We don't want to decay hot callsites to import chains of hot
callsites. The same mechanism is used in LIPO.

Reviewers: tejohnson, eraman, mehdi_amini

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D24976

llvm-svn: 282833
This commit is contained in:
Piotr Padlewski 2016-09-30 03:01:17 +00:00
parent 5d8eb25e78
commit d28694739c
3 changed files with 100 additions and 24 deletions
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27
llvm/lib/Transforms/IPO/FunctionImport.cpp
View File

@ -49,6 +49,13 @@ static cl::opt<float>
"`import-instr-limit` threshold by this factor "
"before processing newly imported functions"));
static cl::opt<float> ImportHotInstrFactor(
"import-hot-evolution-factor", cl::init(1.0), cl::Hidden,
cl::value_desc("x"),
cl::desc("As we import functions called from hot callsite, multiply the "
"`import-instr-limit` threshold by this factor "
"before processing newly imported functions"));
static cl::opt<float> ImportHotMultiplier(
"import-hot-multiplier", cl::init(3.0), cl::Hidden, cl::value_desc("x"),
cl::desc("Multiply the `import-instr-limit` threshold for hot callsites"));
@ -300,6 +307,7 @@ static void computeImportForFunction(
const auto NewThreshold =
Threshold * GetBonusMultiplier(Edge.second.Hotness);
auto *CalleeSummary = selectCallee(GUID, NewThreshold, Index);
if (!CalleeSummary) {
DEBUG(dbgs() << "ignored! No qualifying callee with summary found.\n");
@ -348,8 +356,20 @@ static void computeImportForFunction(
}
}
auto GetAdjustedThreshold = [](unsigned Threshold, bool IsHotCallsite) {
// Adjust the threshold for next level of imported functions.
// The threshold is different for hot callsites because we can then
// inline chains of hot calls.
if (IsHotCallsite)
return Threshold * ImportHotInstrFactor;
return Threshold * ImportInstrFactor;
};
bool IsHotCallsite = Edge.second.Hotness == CalleeInfo::HotnessType::Hot;
// Insert the newly imported function to the worklist.
Worklist.push_back(std::make_pair(ResolvedCalleeSummary, Threshold));
Worklist.emplace_back(ResolvedCalleeSummary,
GetAdjustedThreshold(Threshold, IsHotCallsite));
}
}
@ -380,15 +400,12 @@ static void ComputeImportForModule(
ExportLists);
}
// Process the newly imported functions and add callees to the worklist.
while (!Worklist.empty()) {
auto FuncInfo = Worklist.pop_back_val();
auto *Summary = FuncInfo.first;
auto Threshold = FuncInfo.second;
// Process the newly imported functions and add callees to the worklist.
// Adjust the threshold
Threshold = Threshold * ImportInstrFactor;
computeImportForFunction(*Summary, Index, Threshold, DefinedGVSummaries,
Worklist, ImportList, ExportLists);
}

68
llvm/test/Transforms/FunctionImport/Inputs/hotness_based_import.ll
View File

@ -6,38 +6,76 @@ target triple = "x86_64-unknown-linux-gnu"
define void @hot1() #1 {
ret void
}
define void @hot2() #1 {
call void @externalFunction()
call void @externalFunction()
define void @hot2() #1 !prof !20 {
call void @calledFromHot()
call void @calledFromHot()
ret void
}
define void @hot3() #1 {
call void @externalFunction()
call void @externalFunction()
call void @externalFunction()
define void @hot3() #1 !prof !20 {
call void @calledFromHot()
call void @calledFromHot()
call void @calledFromHot()
ret void
}
define void @cold() #1 {
define void @cold() #1 !prof !0 {
ret void
}
define void @cold2() #1 {
call void @externalFunction()
call void @externalFunction()
define void @cold2() #1 !prof !0 {
call void @calledFromCold()
call void @calledFromCold()
ret void
}
define void @none1() #1 {
ret void
}
define void @none2() #1 {
call void @externalFunction()
call void @calledFromNone()
ret void
}
define void @none3() #1 {
call void @externalFunction()
call void @externalFunction()
call void @calledFromNone()
call void @calledFromNone()
ret void
}
define void @calledFromCold() {
ret void
}
declare void @externalFunction()
define void @calledFromHot() !prof !20 {
call void @calledFromHot2()
ret void
}
define void @calledFromHot2() !prof !20 {
call void @calledFromHot3()
ret void
}
define void @calledFromNone() !prof !0 {
ret void
}
declare void @calledFromHot3()
!0 = !{!"function_entry_count", i64 1}
!20 = !{!"function_entry_count", i64 110}
!llvm.module.flags = !{!1}
!1 = !{i32 1, !"ProfileSummary", !2}
!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
!3 = !{!"ProfileFormat", !"InstrProf"}
!4 = !{!"TotalCount", i64 10000}
!5 = !{!"MaxCount", i64 10}
!6 = !{!"MaxInternalCount", i64 1}
!7 = !{!"MaxFunctionCount", i64 1000}
!8 = !{!"NumCounts", i64 3}
!9 = !{!"NumFunctions", i64 3}
!10 = !{!"DetailedSummary", !11}
!11 = !{!12, !13, !14}
!12 = !{i32 10000, i64 100, i32 1}
!13 = !{i32 999000, i64 100, i32 1}
!14 = !{i32 999999, i64 1, i32 2}

29
llvm/test/Transforms/FunctionImport/hotness_based_import.ll
View File

@ -3,20 +3,38 @@
; RUN: opt -module-summary %p/Inputs/hotness_based_import.ll -o %t2.bc
; RUN: llvm-lto -thinlto -o %t3 %t.bc %t2.bc
; Test import with default hot multiplier (3)
; Test import with default hot multiplier (3) and default hot-evolution-factor (1.0)
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 --S | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-DEFAULT
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 --S -import-hot-multiplier=3.0 -import-cold-multiplier=0.0 | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-DEFAULT
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 --S -import-hot-multiplier=3.0 | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-DEFAULT
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 --S -import-hot-multiplier=3.0 -import-instr-evolution-factor=0.0 | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-DEFAULT
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 --S -import-hot-multiplier=3.0 -import-hot-evolution-factor=1.0 | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-DEFAULT
; HOT-DEFAULT-DAG: define available_externally void @hot1()
; HOT-DEFAULT-DAG: define available_externally void @hot2()
; HOT-DEFAULT-DAG: define available_externally void @calledFromHot()
; HOT-DEFAULT-DAG: define available_externally void @calledFromHot2()
; HOT-DEFAULT-DAG: define available_externally void @none1()
; HOT-DEFAULT-NOT: define available_externally void @cold()
; HOT-DEFAULT-NOT: define available_externally void @hot3()
; HOT-DEFAULT-NOT: define available_externally void @none2()
; HOT-DEFAULT-NOT: define available_externally void @none3()
; HOT-DEFAULT-NOT: define available_externally void @cold2()
; HOT-DEFAULT-NOT: define available_externally void @calledFromCold()
; HOT-DEFAULT-NOT: define available_externally void @calledFromNone()
; This one tests if we decay threshold for hot callsites. With hot-evolution-factor of 0
; we should not import any of calledFromHot functions
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 --S -import-hot-multiplier=3.0 -import-hot-evolution-factor=0.0 | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-EVOLUTION
; HOT-EVOLUTION-DAG: define available_externally void @hot1()
; HOT-EVOLUTION-DAG: define available_externally void @hot2()
; HOT-EVOLUTION-DAG: define available_externally void @none1()
; HOT-EVOLUTION-NOT: define available_externally void @hot3()
; HOT-EVOLUTION-NOT: define available_externally void @cold()
; HOT-EVOLUTION-NOT: define available_externally void @none2()
; HOT-EVOLUTION-NOT: define available_externally void @none3()
; HOT-EVOLUTION-NOT: define available_externally void @cold2()
; HOT-EVOLUTION-NOT: define available_externally void @calledFromHot()
; HOT-EVOLUTION-NOT: define available_externally void @calledFromHot2()
; Test import with hot multiplier 1.0 - treat hot callsites as normal.
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 -import-hot-multiplier=1.0 --S | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-ONE
@ -46,10 +64,13 @@
; HOT-ZERO-DAG: define available_externally void @none2()
; HOT-ZERO-DAG: define available_externally void @none3()
; HOT-ZERO-DAG: define available_externally void @cold2()
; HOT-ZERO-DAG: define available_externally void @calledFromCold()
; HOT-ZERO-DAG: define available_externally void @calledFromNone()
; HOT-ZERO-NOT: define available_externally void @hot2()
; HOT-ZERO-NOT: define available_externally void @hot1()
; HOT-ZERO-NOT: define available_externally void @hot3()
; HOT-ZERO-NOT: define available_externally void @calledFromHot()
; HOT-ZERO-NOT: define available_externally void @calledFromHot2()
; ModuleID = 'thinlto-function-summary-callgraph.ll'