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[profile] value profiling bug fix -- missing icall targets in profile-use

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Inline virtual functions has linkeonceodr linkage (emitted in comdat on 
supporting targets). If the vtable for the class is not emitted in the
defining module, function won't be address taken thus its address is not
recorded. At the mercy of the linker, if the per-func prf_data from this
module (in comdat) is picked at link time, we will lose mapping from
function address to its hash val. This leads to missing icall promotion.
The second test case (currently disabled) in compiler_rt (r271528): 
instrprof-icall-prom.test demostrates the bug. The first profile-use
subtest is fine due to linker order difference.

With this change, no missing icall targets is found in instrumented clang's
raw profile.

llvm-svn: 271532
This commit is contained in:
Xinliang David Li 2016-06-02 16:33:41 +00:00
parent 4ea9d7ec0b
commit 09755f1a0a
3 changed files with 20 additions and 3 deletions
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8
lib/Transforms/Instrumentation/InstrProfiling.cpp
View File

@ -258,7 +258,13 @@ static inline bool shouldRecordFunctionAddr(Function *F) {
if (F->hasLocalLinkage() && F->hasComdat())
return false;
// Check uses of this function for other than direct calls or invokes to it.
return F->hasAddressTaken();
// Inline virtual functions have linkeOnceODR linkage. When a key method
// exists, the vtable will only be emitted in the TU where the key method
// is defined. In a TU where vtable is not available, the function won't
// be 'addresstaken'. If its address is not recorded here, the profile counter
// comdat group with missing address may be picked by the linker leading
// to missing indirect call target info.
return F->hasAddressTaken() || (F->hasLinkOnceLinkage() && F->hasComdat());
}
static inline bool needsComdatForCounter(Function &F, Module &M) {

4
test/Instrumentation/InstrProfiling/PR23499.ll
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@ -15,13 +15,13 @@ $_Z3barIvEvv = comdat any
; CHECK: @__profn__Z3barIvEvv = private constant [11 x i8] c"_Z3barIvEvv", align 1
; CHECK: @__profc__Z3barIvEvv = linkonce_odr hidden global [1 x i64] zeroinitializer, section "{{.*}}__llvm_prf_cnts", comdat($__profv__Z3barIvEvv), align 8
; CHECK: @__profd__Z3barIvEvv = linkonce_odr hidden global { i64, i64, i64*, i8*, i8*, i32, [1 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8* null, i8* null, i32 1, [1 x i16] zeroinitializer }, section "{{.*}}__llvm_prf_data", comdat($__profv__Z3barIvEvv), align 8
; CHECK: @__profd__Z3barIvEvv = linkonce_odr hidden global { i64, i64, i64*, i8*, i8*, i32, [1 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8*{{.*}}, i8* null, i32 1, [1 x i16] zeroinitializer }, section "{{.*}}__llvm_prf_data", comdat($__profv__Z3barIvEvv), align 8
; CHECK: @__llvm_prf_nm = private constant [{{.*}} x i8] c"{{.*}}", section "{{.*}}__llvm_prf_names"
; COFF: @__profn__Z3barIvEvv = private constant [11 x i8] c"_Z3barIvEvv", align 1
; COFF: @__profc__Z3barIvEvv = linkonce_odr hidden global [1 x i64] zeroinitializer, section "{{.*}}__llvm_prf_cnts", comdat, align 8
; COFF: @__profd__Z3barIvEvv = linkonce_odr hidden global { i64, i64, i64*, i8*, i8*, i32, [1 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8* null, i8* null, i32 1, [1 x i16] zeroinitializer }, section "{{.*}}__llvm_prf_data", comdat($__profc__Z3barIvEvv), align 8
; COFF: @__profd__Z3barIvEvv = linkonce_odr hidden global { i64, i64, i64*, i8*, i8*, i32, [1 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8*{{.*}}, i8* null, i32 1, [1 x i16] zeroinitializer }, section "{{.*}}__llvm_prf_data", comdat($__profc__Z3barIvEvv), align 8
declare void @llvm.instrprof.increment(i8*, i64, i32, i32) #1

11
test/Transforms/PGOProfile/indirect_call_profile.ll
View File

@ -1,8 +1,12 @@
; RUN: opt < %s -pgo-instr-gen -S | FileCheck %s --check-prefix=GEN
; RUN: opt < %s -passes=pgo-instr-gen -S | FileCheck %s --check-prefix=GEN
; RUN: opt < %s -passes=pgo-instr-gen,instrprof -S | FileCheck %s --check-prefix=LOWER
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
$foo3 = comdat any
@bar = external global void ()*, align 8
; GEN: @__profn_foo = private constant [3 x i8] c"foo"
@ -49,6 +53,13 @@ bb11: ; preds = %bb2
resume { i8*, i32 } %tmp3
}
; Test that comdat function's address is recorded.
; LOWER: @__profd_foo3 = linkonce_odr{{.*}}@foo3
; Function Attrs: nounwind uwtable
define linkonce_odr i32 @foo3() comdat {
ret i32 1
}
declare i32 @__gxx_personality_v0(...)
; Function Attrs: nounwind readnone