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[thinlto] Add cold-callsite import heuristic 

Summary:
Not tunned up heuristic, but with this small heuristic there is about
+0.10% improvement on SPEC 2006

Reviewers: tejohnson, mehdi_amini, eraman

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D24940

llvm-svn: 282733
This commit is contained in:
Piotr Padlewski 2016-09-29 17:32:07 +00:00
parent 3ace13adfa
commit ba72b95f7b
2 changed files with 30 additions and 10 deletions
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22
llvm/lib/Transforms/IPO/FunctionImport.cpp
View File

@ -48,10 +48,15 @@ static cl::opt<float>
cl::desc("As we import functions, 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::ZeroOrMore, cl::desc("Multiply the `import-instr-limit` threshold for "
"hot callsites"));
cl::desc("Multiply the `import-instr-limit` threshold for hot callsites"));
// FIXME: This multiplier was not really tuned up.
static cl::opt<float> ImportColdMultiplier(
"import-cold-multiplier", cl::init(0), cl::Hidden, cl::value_desc("N"),
cl::desc("Multiply the `import-instr-limit` threshold for cold callsites"));
static cl::opt<bool> PrintImports("print-imports", cl::init(false), cl::Hidden,
cl::desc("Print imported functions"));
@ -285,11 +290,16 @@ static void computeImportForFunction(
continue;
}
// FIXME: Also lower the threshold for cold callsites.
auto GetBonusMultiplier = [](CalleeInfo::HotnessType Hotness) -> float {
if (Hotness == CalleeInfo::HotnessType::Hot)
return ImportHotMultiplier;
if (Hotness == CalleeInfo::HotnessType::Cold)
return ImportColdMultiplier;
return 1.0;
};
const auto NewThreshold =
Edge.second.Hotness == CalleeInfo::HotnessType::Hot
? Threshold * ImportHotMultiplier
: Threshold;
Threshold * GetBonusMultiplier(Edge.second.Hotness);
auto *CalleeSummary = selectCallee(GUID, NewThreshold, Index);
if (!CalleeSummary) {
DEBUG(dbgs() << "ignored! No qualifying callee with summary found.\n");

18
llvm/test/Transforms/FunctionImport/hotness_based_import.ll
View File

@ -5,12 +5,13 @@
; Test import with default hot multiplier (3)
; 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 | 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
; HOT-DEFAULT-DAG: define available_externally void @hot1()
; HOT-DEFAULT-DAG: define available_externally void @hot2()
; HOT-DEFAULT-DAG: define available_externally void @cold()
; 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()
@ -20,17 +21,26 @@
; 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
; HOT-ONE-DAG: define available_externally void @hot1()
; HOT-ONE-DAG: define available_externally void @cold()
; HOT-ONE-DAG: define available_externally void @none1()
; HOT-ONE-NOT: define available_externally void @cold()
; HOT-ONE-NOT: define available_externally void @hot2()
; HOT-ONE-NOT: define available_externally void @hot3()
; HOT-ONE-NOT: define available_externally void @none2()
; HOT-ONE-NOT: define available_externally void @none3()
; HOT-ONE-NOT: define available_externally void @cold2()
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=1 -import-hot-multiplier=1.0 -import-cold-multiplier=1.0 --S | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-COLD-ONE
; HOT-COLD-ONE-DAG: define available_externally void @hot1()
; HOT-COLD-ONE-DAG: define available_externally void @cold()
; HOT-COLD-ONE-DAG: define available_externally void @none1()
; HOT-COLD-ONE-NOT: define available_externally void @hot2()
; HOT-COLD-ONE-NOT: define available_externally void @hot3()
; HOT-COLD-ONE-NOT: define available_externally void @none2()
; HOT-COLD-ONE-NOT: define available_externally void @none3()
; HOT-COLD-ONE-NOT: define available_externally void @cold2()
; Test import with hot multiplier 0.0 and high threshold - don't import functions called from hot callsite.
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=10 -import-hot-multiplier=0.0 --S | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-ZERO
; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=10 -import-hot-multiplier=0.0 -import-cold-multiplier=1.0 --S | FileCheck %s --check-prefix=CHECK --check-prefix=HOT-ZERO
; HOT-ZERO-DAG: define available_externally void @cold()
; HOT-ZERO-DAG: define available_externally void @none1()
; HOT-ZERO-DAG: define available_externally void @none2()