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teresajohnsonteresajohnson
committedFeb 7, 2018
[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
1 parent 37a4a8a commit f368101

13 files changed

+48
-0
lines changed
 

‎llvm/include/llvm/Bitcode/LLVMBitCodes.h

+2
Original file line numberDiff line numberDiff line change
@@ -261,6 +261,8 @@ enum GlobalValueSummarySymtabCodes {
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// numrefs x valueid,
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// n x (valueid, relblockfreq)]
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FS_PERMODULE_RELBF = 19,
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// Index-wide flags
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FS_FLAGS = 20,
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};
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enum MetadataCodes {

‎llvm/lib/Bitcode/Reader/BitcodeReader.cpp

+10
Original file line numberDiff line numberDiff line change
@@ -5133,6 +5133,16 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
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switch (BitCode) {
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default: // Default behavior: ignore.
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break;
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case bitc::FS_FLAGS: { // [flags]
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uint64_t Flags = Record[0];
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// Scan flags (set only on the combined index).
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assert(Flags <= 1 && "Unexpected bits in flag");
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// 1 bit: WithGlobalValueDeadStripping flag.
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if (Flags & 0x1)
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TheIndex.setWithGlobalValueDeadStripping();
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break;
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}
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case bitc::FS_VALUE_GUID: { // [valueid, refguid]
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uint64_t ValueID = Record[0];
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GlobalValue::GUID RefGUID = Record[1];

‎llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

+5
Original file line numberDiff line numberDiff line change
@@ -3552,6 +3552,11 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
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Stream.EnterSubblock(bitc::GLOBALVAL_SUMMARY_BLOCK_ID, 3);
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Stream.EmitRecord(bitc::FS_VERSION, ArrayRef<uint64_t>{INDEX_VERSION});
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// Write the index flags. Currently we only write a single flag, the value of
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// withGlobalValueDeadStripping, which only applies to the combined index.
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Stream.EmitRecord(bitc::FS_FLAGS,
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ArrayRef<uint64_t>{Index.withGlobalValueDeadStripping()});
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for (const auto &GVI : valueIds()) {
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Stream.EmitRecord(bitc::FS_VALUE_GUID,
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ArrayRef<uint64_t>{GVI.second, GVI.first});

‎llvm/test/Bitcode/thinlto-alias.ll

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

‎llvm/test/Bitcode/thinlto-deadstrip-flag.ll

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

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

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

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

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

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

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Original file line numberDiff line numberDiff line change
@@ -39,6 +39,7 @@
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; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
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; COMBINED-NEXT: <VERSION
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; COMBINED-NEXT: <FLAGS
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID
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; COMBINED-NEXT: <VALUE_GUID

‎llvm/test/Bitcode/thinlto-function-summary-callgraph.ll

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

‎llvm/test/Bitcode/thinlto-function-summary-originalnames.ll

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@@ -5,6 +5,7 @@
55

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; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
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; COMBINED-NEXT: <VERSION
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; COMBINED-NEXT: <FLAGS
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; COMBINED-NEXT: <VALUE_GUID {{.*}} op1=4947176790635855146/>
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; COMBINED-NEXT: <VALUE_GUID {{.*}} op1=-6591587165810580810/>
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; COMBINED-NEXT: <VALUE_GUID {{.*}} op1=-4377693495213223786/>

‎llvm/test/tools/gold/X86/thinlto.ll

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

‎llvm/test/tools/llvm-lto/thinlto.ll

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

‎llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp

+1
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@@ -315,6 +315,7 @@ static const char *GetCodeName(unsigned CodeID, unsigned BlockID,
315315
STRINGIFY_CODE(FS, COMBINED_ALIAS)
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STRINGIFY_CODE(FS, COMBINED_ORIGINAL_NAME)
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STRINGIFY_CODE(FS, VERSION)
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STRINGIFY_CODE(FS, FLAGS)
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STRINGIFY_CODE(FS, TYPE_TESTS)
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STRINGIFY_CODE(FS, TYPE_TEST_ASSUME_VCALLS)
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STRINGIFY_CODE(FS, TYPE_CHECKED_LOAD_VCALLS)

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