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[PGO] Add a functionality to always instrument the func entry BB 

Add an option to always instrument function entry BB (default off)
Add an option to do atomically updates on the first counter in each
instrumented function.

Differential Revision: https://reviews.llvm.org/D82123
This commit is contained in:
Rong Xu 2020-06-26 10:20:09 -07:00
parent 9c98ed9cd4
commit b4bceb94ee
3 changed files with 73 additions and 2 deletions
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16
llvm/lib/Transforms/Instrumentation/CFGMST.h
View File

@ -20,6 +20,7 @@
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
@ -28,6 +29,11 @@
#define DEBUG_TYPE "cfgmst"
using namespace llvm;
static cl::opt<bool> PGOInstrumentEntry(
"pgo-instrument-entry", cl::init(false), cl::Hidden,
cl::desc("Force to instrument function entry basicblock."));
namespace llvm {
/// An union-find based Minimum Spanning Tree for CFG
@ -100,8 +106,11 @@ public:
const BasicBlock *Entry = &(F.getEntryBlock());
uint64_t EntryWeight = (BFI != nullptr ? BFI->getEntryFreq() : 2);
// If we want to instrument the entry count, lower the weight to 0.
if (PGOInstrumentEntry)
EntryWeight = 0;
Edge *EntryIncoming = nullptr, *EntryOutgoing = nullptr,
*ExitOutgoing = nullptr, *ExitIncoming = nullptr;
*ExitOutgoing = nullptr, *ExitIncoming = nullptr;
uint64_t MaxEntryOutWeight = 0, MaxExitOutWeight = 0, MaxExitInWeight = 0;
// Add a fake edge to the entry.
@ -135,6 +144,8 @@ public:
}
if (BPI != nullptr)
Weight = BPI->getEdgeProbability(&*BB, TargetBB).scale(scaleFactor);
if (Weight == 0)
Weight++;
auto *E = &addEdge(&*BB, TargetBB, Weight);
E->IsCritical = Critical;
LLVM_DEBUG(dbgs() << " Edge: from " << BB->getName() << " to "
@ -278,6 +289,9 @@ public:
buildEdges();
sortEdgesByWeight();
computeMinimumSpanningTree();
if (PGOInstrumentEntry && (AllEdges.size() > 1))
std::iter_swap(std::move(AllEdges.begin()),
std::move(AllEdges.begin() + AllEdges.size() - 1));
}
};

9
llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
View File

@ -110,6 +110,12 @@ cl::opt<bool> AtomicCounterUpdatePromoted(
" for promoted counters only"),
cl::init(false));
cl::opt<bool> AtomicFirstCounter(
"atomic-first-counter", cl::ZeroOrMore,
cl::desc("Use atomic fetch add for first counter in a function (usually "
"the entry counter)"),
cl::init(false));
// If the option is not specified, the default behavior about whether
// counter promotion is done depends on how instrumentaiton lowering
// pipeline is setup, i.e., the default value of true of this option
@ -696,7 +702,8 @@ void InstrProfiling::lowerIncrement(InstrProfIncrementInst *Inc) {
Addr = Builder.CreateIntToPtr(Add, Int64PtrTy);
}
if (Options.Atomic || AtomicCounterUpdateAll) {
if (Options.Atomic || AtomicCounterUpdateAll ||
(Index == 0 && AtomicFirstCounter)) {
Builder.CreateAtomicRMW(AtomicRMWInst::Add, Addr, Inc->getStep(),
AtomicOrdering::Monotonic);
} else {

50
llvm/test/Transforms/PGOProfile/instr_entry_bb.ll Normal file
View File

@ -0,0 +1,50 @@
; RUN: opt < %s -pgo-instr-gen -pgo-instrument-entry -S | FileCheck %s --check-prefix=GEN
; RUN: opt < %s -passes=pgo-instr-gen -pgo-instrument-entry -S | FileCheck %s --check-prefix=GEN
; RUN: opt < %s -pgo-instr-gen -pgo-instrument-entry -instrprof -atomic-first-counter -S | FileCheck %s --check-prefix=GENA
; RUN: opt < %s -passes=pgo-instr-gen,instrprof -pgo-instrument-entry -atomic-first-counter -S | FileCheck %s --check-prefix=GENA
; RUN: llvm-profdata merge %S/Inputs/branch2.proftext -o %t.profdata
; RUN: opt < %s -pgo-instr-use -pgo-test-profile-file=%t.profdata -pgo-instrument-entry -S | FileCheck %s --check-prefix=USE
; RUN: opt < %s -passes=pgo-instr-use -pgo-test-profile-file=%t.profdata -pgo-instrument-entry -S | FileCheck %s --check-prefix=USE
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; GEN: $__llvm_profile_raw_version = comdat any
; GEN: @__llvm_profile_raw_version = constant i64 {{[0-9]+}}, comdat
; GEN: @__profn_test_br_2 = private constant [9 x i8] c"test_br_2"
define i32 @test_br_2(i32 %i) {
entry:
; GEN: entry:
; GEN: call void @llvm.instrprof.increment(i8* getelementptr inbounds ([9 x i8], [9 x i8]* @__profn_test_br_2, i32 0, i32 0), i64 29667547796, i32 2, i32 0)
; GENA: entry:
; GENA: %{{[0-9+]}} = atomicrmw add i64* getelementptr inbounds ([2 x i64], [2 x i64]* @__profc_test_br_2, i64 0, i64 0), i64 1 monotonic
; USE: br i1 %cmp, label %if.then, label %if.else
; USE-SAME: !prof ![[BW_ENTRY:[0-9]+]]
; USE: ![[BW_ENTRY]] = !{!"branch_weights", i32 0, i32 1}
%cmp = icmp sgt i32 %i, 0
br i1 %cmp, label %if.then, label %if.else
if.then:
; GEN: if.then:
; GEN-NOT: llvm.instrprof.increment
%add = add nsw i32 %i, 2
br label %if.end
if.else:
; GEN: if.else:
; GEN: call void @llvm.instrprof.increment(i8* getelementptr inbounds ([9 x i8], [9 x i8]* @__profn_test_br_2, i32 0, i32 0), i64 29667547796, i32 2, i32 1)
; GENA: if.else:
; GENA: %pgocount = load i64, i64* getelementptr inbounds ([2 x i64], [2 x i64]* @__profc_test_br_2, i64 0, i64 1), align 8
; GENA: [[V:%[0-9]*]] = add i64 %pgocount, 1
; GENA: store i64 [[V]], i64* getelementptr inbounds ([2 x i64], [2 x i64]* @__profc_test_br_2, i64 0, i64 1), align 8
%sub = sub nsw i32 %i, 2
br label %if.end
if.end:
; GEN: if.end:
; GEN-NOT: llvm.instrprof.increment
%retv = phi i32 [ %add, %if.then ], [ %sub, %if.else ]
ret i32 %retv
; GEN: ret
}