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[PartialInlining] Emit branch info and profile data as remarks

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This allows us to collect profile statistics to tune static 
branch prediction.

Differential Revision: http://reviews.llvm.org/D33746

llvm-svn: 304452
This commit is contained in:
Xinliang David Li 2017-06-01 18:58:50 +00:00
parent 023cde2142
commit 3b7bd84df1
2 changed files with 69 additions and 0 deletions
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64
lib/Transforms/Instrumentation/PGOInstrumentation.cpp
View File

@ -182,6 +182,14 @@ static cl::opt<bool>
cl::desc("Use this option to turn on/off "
"memory intrinsic size profiling."));
// Emit branch probability as optimization remarks.
static cl::opt<bool>
EmitBranchProbability("pgo-emit-branch-prob", cl::init(false), cl::Hidden,
cl::desc("When this option is on, the annotated "
"branch probability will be emitted as "
" optimization remarks: -Rpass-analysis="
"pgo-instr-use"));
// Command line option to turn on CFG dot dump after profile annotation.
// Defined in Analysis/BlockFrequencyInfo.cpp: -pgo-view-counts
extern cl::opt<bool> PGOViewCounts;
@ -192,6 +200,39 @@ extern cl::opt<std::string> ViewBlockFreqFuncName;
namespace {
// Return a string describing the branch condition that can be
// used in static branch probability heuristics:
std::string getBranchCondString(Instruction *TI) {
BranchInst *BI = dyn_cast<BranchInst>(TI);
if (!BI || !BI->isConditional())
return std::string();
Value *Cond = BI->getCondition();
ICmpInst *CI = dyn_cast<ICmpInst>(Cond);
if (!CI)
return std::string();
std::string result;
raw_string_ostream OS(result);
OS << CmpInst::getPredicateName(CI->getPredicate()) << "_";
CI->getOperand(0)->getType()->print(OS, true);
Value *RHS = CI->getOperand(1);
ConstantInt *CV = dyn_cast<ConstantInt>(RHS);
if (CV) {
if (CV->isZero())
OS << "_Zero";
else if (CV->isOne())
OS << "_One";
else if (CV->isAllOnesValue())
OS << "_MinusOne";
else
OS << "_Const";
}
OS.flush();
return result;
}
/// The select instruction visitor plays three roles specified
/// by the mode. In \c VM_counting mode, it simply counts the number of
/// select instructions. In \c VM_instrument mode, it inserts code to count
@ -1424,6 +1465,29 @@ void setProfMetadata(Module *M, Instruction *TI, ArrayRef<uint64_t> EdgeCounts,
for (const auto &W : Weights) { dbgs() << W << " "; }
dbgs() << "\n";);
TI->setMetadata(llvm::LLVMContext::MD_prof, MDB.createBranchWeights(Weights));
if (EmitBranchProbability) {
std::string BrCondStr = getBranchCondString(TI);
if (BrCondStr.empty())
return;
unsigned WSum =
std::accumulate(Weights.begin(), Weights.end(), 0,
[](unsigned w1, unsigned w2) { return w1 + w2; });
uint64_t TotalCount =
std::accumulate(EdgeCounts.begin(), EdgeCounts.end(), 0,
[](uint64_t c1, uint64_t c2) { return c1 + c2; });
BranchProbability BP(Weights[0], WSum);
std::string BranchProbStr;
raw_string_ostream OS(BranchProbStr);
OS << BP;
OS << " (total count : " << TotalCount << ")";
OS.flush();
Function *F = TI->getParent()->getParent();
emitOptimizationRemarkAnalysis(
F->getContext(), "pgo-use-annot", *F, TI->getDebugLoc(),
Twine(BrCondStr) +
" is true with probability : " + Twine(BranchProbStr));
}
}
template <> struct GraphTraits<PGOUseFunc *> {

5
test/Transforms/PGOProfile/branch1.ll
View File

@ -15,6 +15,9 @@
; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -S | FileCheck %s --check-prefix=USE
; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.l.profdata -S | FileCheck %s --check-prefix=USE-LARGE
; RUN: opt < %s -pgo-instr-use -pgo-test-profile-file=%t.profdata -pass-remarks-analysis=pgo-use-annot -pgo-emit-branch-prob -S 2>&1| FileCheck %s --check-prefix=ANALYSIS
; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -pass-remarks-analysis=pgo-use-annot -pgo-emit-branch-prob -S 2>&1| FileCheck %s --check-prefix=ANALYSIS
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; GEN-DARWIN-LINKONCE: target triple = "x86_64-apple-darwin"
@ -54,3 +57,5 @@ if.end:
; USE-DAG: {{![0-9]+}} = !{i32 1, !"ProfileSummary", {{![0-9]+}}}
; USE-DAG: {{![0-9]+}} = !{!"DetailedSummary", {{![0-9]+}}}
; USE-DAG: ![[FUNC_ENTRY_COUNT]] = !{!"function_entry_count", i64 3}
; ANALYSIS:remark: <unknown>:0:0: sgt_i32_Zero {{.*}}66.67% (total count : 3)