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[ThinLTO] Serialize WithGlobalValueDeadStripping index flag for distributed backends 

Summary:
A recent fix to drop dead symbols (r323633) did not work for ThinLTO
distributed backends because we lose the WithGlobalValueDeadStripping
set on the index during the thin link. This patch adds a new flags
record to the bitcode format for the index, and serializes this flag
for the combined index (it would always be 0 for the per-module index
generated by the compile step, so no need to serialize the new flags
record there until/unless we add another flag that applies to the
per-module indexes).

Generally this flag should always be set for the distributed backends,
which are necessarily performed after the thin link. However, if we were
to simply set this flag on the index applied to the distributed backends
(invoked via clang), we would lose the ability to disable dead stripping
via -compute-dead=false for debugging purposes.

Reviewers: grimar, pcc

Subscribers: mehdi_amini, inglorion, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D42799

llvm-svn: 324444
This commit is contained in:
Teresa Johnson 2018-02-07 04:05:59 +00:00
parent 37a4a8a4b1
commit f368101567
13 changed files with 48 additions and 0 deletions
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2
llvm/include/llvm/Bitcode/LLVMBitCodes.h
View File

@ -261,6 +261,8 @@ enum GlobalValueSummarySymtabCodes {
// numrefs x valueid,
// n x (valueid, relblockfreq)]
FS_PERMODULE_RELBF = 19,
// Index-wide flags
FS_FLAGS = 20,
};
enum MetadataCodes {

10
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
View File

@ -5133,6 +5133,16 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
switch (BitCode) {
default: // Default behavior: ignore.
break;
case bitc::FS_FLAGS: { // [flags]
uint64_t Flags = Record[0];
// Scan flags (set only on the combined index).
assert(Flags <= 1 && "Unexpected bits in flag");
// 1 bit: WithGlobalValueDeadStripping flag.
if (Flags & 0x1)
TheIndex.setWithGlobalValueDeadStripping();
break;
}
case bitc::FS_VALUE_GUID: { // [valueid, refguid]
uint64_t ValueID = Record[0];
GlobalValue::GUID RefGUID = Record[1];

5
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -3552,6 +3552,11 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
Stream.EnterSubblock(bitc::GLOBALVAL_SUMMARY_BLOCK_ID, 3);
Stream.EmitRecord(bitc::FS_VERSION, ArrayRef<uint64_t>{INDEX_VERSION});
// Write the index flags. Currently we only write a single flag, the value of
// withGlobalValueDeadStripping, which only applies to the combined index.
Stream.EmitRecord(bitc::FS_FLAGS,
ArrayRef<uint64_t>{Index.withGlobalValueDeadStripping()});
for (const auto &GVI : valueIds()) {
Stream.EmitRecord(bitc::FS_VALUE_GUID,
ArrayRef<uint64_t>{GVI.second, GVI.first});

1
llvm/test/Bitcode/thinlto-alias.ll
View File

@ -22,6 +22,7 @@
; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; See if the call to analias is registered, using the expected value id.
; COMBINED-NEXT: <VALUE_GUID op0=[[ALIASID:[0-9]+]] op1=-5751648690987223394/>
; COMBINED-NEXT: <VALUE_GUID

20
llvm/test/Bitcode/thinlto-deadstrip-flag.ll Normal file
View File

@ -0,0 +1,20 @@
; REQUIRES: x86-registered-target
; RUN: opt -module-summary %s -o %t.o
; Ensure dead stripping performed flag is set on distributed index
; RUN: llvm-lto2 run %t.o -o %t.out -thinlto-distributed-indexes \
; RUN: -r %t.o,glob,plx
; RUN: llvm-bcanalyzer -dump %t.o.thinlto.bc | FileCheck %s --check-prefix=WITHDEAD
; WITHDEAD: <FLAGS op0=1/>
; Ensure dead stripping performed flag is not set on distributed index
; when option used to disable dead stripping computation.
; RUN: llvm-lto2 run %t.o -o %t.out -thinlto-distributed-indexes \
; RUN: -r %t.o,glob,plx -compute-dead=false
; RUN: llvm-bcanalyzer -dump %t.o.thinlto.bc | FileCheck %s --check-prefix=NODEAD
; NODEAD: <FLAGS op0=0/>
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@glob = global i32 0

1
llvm/test/Bitcode/thinlto-function-summary-callgraph-pgo.ll
View File

@ -24,6 +24,7 @@
; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; COMBINED-NEXT: <VALUE_GUID op0=[[FUNCID:[0-9]+]] op1=7289175272376759421/>
; COMBINED-NEXT: <VALUE_GUID
; COMBINED-NEXT: <COMBINED

1
llvm/test/Bitcode/thinlto-function-summary-callgraph-profile-summary.ll
View File

@ -37,6 +37,7 @@
; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; COMBINED-NEXT: <VALUE_GUID
; COMBINED-NEXT: <VALUE_GUID
; COMBINED-NEXT: <VALUE_GUID

1
llvm/test/Bitcode/thinlto-function-summary-callgraph-sample-profile-summary.ll
View File

@ -39,6 +39,7 @@
; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; COMBINED-NEXT: <VALUE_GUID
; COMBINED-NEXT: <VALUE_GUID
; COMBINED-NEXT: <VALUE_GUID

1
llvm/test/Bitcode/thinlto-function-summary-callgraph.ll
View File

@ -26,6 +26,7 @@
; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; Only 2 VALUE_GUID since reference to undefinedglob should not be included in
; combined index.
; COMBINED-NEXT: <VALUE_GUID op0=[[FUNCID:[0-9]+]] op1=7289175272376759421/>

1
llvm/test/Bitcode/thinlto-function-summary-originalnames.ll
View File

@ -5,6 +5,7 @@
; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; COMBINED-NEXT: <VALUE_GUID {{.*}} op1=4947176790635855146/>
; COMBINED-NEXT: <VALUE_GUID {{.*}} op1=-6591587165810580810/>
; COMBINED-NEXT: <VALUE_GUID {{.*}} op1=-4377693495213223786/>

3
llvm/test/tools/gold/X86/thinlto.ll
View File

@ -95,6 +95,7 @@
; BACKEND1-NEXT: </MODULE_STRTAB_BLOCK
; BACKEND1-NEXT: <GLOBALVAL_SUMMARY_BLOCK
; BACKEND1-NEXT: <VERSION
; BACKEND1-NEXT: <FLAGS
; BACKEND1-NEXT: <VALUE_GUID op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
; BACKEND1-NEXT: <VALUE_GUID op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
; BACKEND1-NEXT: <COMBINED
@ -108,6 +109,7 @@
; BACKEND2-NEXT: </MODULE_STRTAB_BLOCK
; BACKEND2-NEXT: <GLOBALVAL_SUMMARY_BLOCK
; BACKEND2-NEXT: <VERSION
; BACKEND2-NEXT: <FLAGS
; BACKEND2-NEXT: <VALUE_GUID op0=1 op1=-5300342847281564238
; BACKEND2-NEXT: <COMBINED
; BACKEND2-NEXT: </GLOBALVAL_SUMMARY_BLOCK
@ -118,6 +120,7 @@
; COMBINED-NEXT: </MODULE_STRTAB_BLOCK
; COMBINED-NEXT: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; COMBINED-NEXT: <VALUE_GUID op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
; COMBINED-NEXT: <VALUE_GUID op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
; COMBINED-NEXT: <COMBINED

1
llvm/test/tools/llvm-lto/thinlto.ll
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@ -11,6 +11,7 @@
; COMBINED-NEXT: </MODULE_STRTAB_BLOCK
; COMBINED-NEXT: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <FLAGS
; COMBINED-NEXT: <VALUE_GUID op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
; COMBINED-NEXT: <VALUE_GUID op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
; COMBINED-NEXT: <COMBINED

1
llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
View File

@ -315,6 +315,7 @@ static const char *GetCodeName(unsigned CodeID, unsigned BlockID,
STRINGIFY_CODE(FS, COMBINED_ALIAS)
STRINGIFY_CODE(FS, COMBINED_ORIGINAL_NAME)
STRINGIFY_CODE(FS, VERSION)
STRINGIFY_CODE(FS, FLAGS)
STRINGIFY_CODE(FS, TYPE_TESTS)
STRINGIFY_CODE(FS, TYPE_TEST_ASSUME_VCALLS)
STRINGIFY_CODE(FS, TYPE_CHECKED_LOAD_VCALLS)