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[PGO] Remove redundant VP instrumentation

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LLVM optimization passes may reduce a profiled target expression
to a constant. Removing runtime calls at such instrumentation points
would help speedup the runtime of the instrumented program.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266229 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Betul Buyukkurt 2016-04-13 18:52:19 +00:00
parent b935913676
commit 5a486ec618
2 changed files with 35 additions and 0 deletions
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16
lib/Transforms/Scalar/ADCE.cpp
View File

@ -27,6 +27,7 @@
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Transforms/Scalar.h"
using namespace llvm;
@ -61,6 +62,17 @@ static void collectLiveScopes(const DILocation &DL,
collectLiveScopes(*IA, AliveScopes);
}
// Check if this instruction is a runtime call for value profiling and
// if it's instrumenting a constant.
static bool isInstrumentsConstant(Instruction &I) {
if (CallInst *CI = dyn_cast<CallInst>(&I))
if (Function *Callee = CI->getCalledFunction())
if (Callee->getName().equals(getInstrProfValueProfFuncName()))
if (isa<Constant>(CI->getArgOperand(0)))
return true;
return false;
}
static bool aggressiveDCE(Function& F) {
SmallPtrSet<Instruction*, 32> Alive;
SmallVector<Instruction*, 128> Worklist;
@ -68,6 +80,10 @@ static bool aggressiveDCE(Function& F) {
// Collect the set of "root" instructions that are known live.
for (Instruction &I : instructions(F)) {
if (isa<TerminatorInst>(I) || I.isEHPad() || I.mayHaveSideEffects()) {
// Skip any value profile instrumentation calls if they are
// instrumenting constants.
if (isInstrumentsConstant(I))
continue;
Alive.insert(&I);
Worklist.push_back(&I);
}

19
test/Transforms/ADCE/delete-profiling-calls-to-constant.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: opt < %s -adce | FileCheck %s
; RUN: opt < %s -passes=adce | FileCheck %s
; Verify that a call to instrument a constant is deleted.
@__profc_foo = private global [1 x i64] zeroinitializer, section "__llvm_prf_cnts", align 8
@__profd_foo = private global { i64, i64, i64*, i8*, i8*, i32, [1 x i16] } { i64 6699318081062747564, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_foo, i32 0, i32 0), i8* bitcast (i32 ()* @foo to i8*), i8* null, i32 1, [1 x i16] [i16 1] }, section "__llvm_prf_data", align 8
define i32 @foo() {
; CHECK-NOT: __llvm_profile_instrument_target
entry:
tail call void @__llvm_profile_instrument_target(i64 ptrtoint (i32 (i32)* @bar to i64), i8* bitcast ({ i64, i64, i64*, i8*, i8*, i32, [1 x i16] }* @__profd_foo to i8*), i32 0)
%call = tail call i32 @bar(i32 21)
ret i32 %call
}
declare i32 @bar(i32)
declare void @__llvm_profile_instrument_target(i64, i8*, i32)