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[ThinLTO] Thin link efficiency improvement: don't re-export globals (NFC)

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Summary:
We were reinvoking exportGlobalInModule numerous times redundantly.
No need to re-export globals referenced by a global that was already
imported from its module. This resulted in a large speedup in the thin
link for a big application, particularly when importing aggressiveness
was cranked up.

Reviewers: mehdi_amini

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D27687

llvm-svn: 289896
This commit is contained in:
Teresa Johnson 2016-12-15 23:50:06 +00:00
parent 73e0a445d1
commit d81c3fc8d1
3 changed files with 49 additions and 9 deletions
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22
lib/Transforms/IPO/FunctionImport.cpp
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@ -338,6 +338,7 @@ static void computeImportForFunction(
<< ProcessedThreshold << "\n");
continue;
}
bool PreviouslyImported = ProcessedThreshold != 0;
// Mark this function as imported in this module, with the current Threshold
ProcessedThreshold = AdjThreshold;
@ -345,15 +346,18 @@ static void computeImportForFunction(
if (ExportLists) {
auto &ExportList = (*ExportLists)[ExportModulePath];
ExportList.insert(GUID);
// Mark all functions and globals referenced by this function as exported
// to the outside if they are defined in the same source module.
for (auto &Edge : ResolvedCalleeSummary->calls()) {
auto CalleeGUID = Edge.first.getGUID();
exportGlobalInModule(Index, ExportModulePath, CalleeGUID, ExportList);
}
for (auto &Ref : ResolvedCalleeSummary->refs()) {
auto GUID = Ref.getGUID();
exportGlobalInModule(Index, ExportModulePath, GUID, ExportList);
if (!PreviouslyImported) {
// This is the first time this function was exported from its source
// module, so mark all functions and globals it references as exported
// to the outside if they are defined in the same source module.
for (auto &Edge : ResolvedCalleeSummary->calls()) {
auto CalleeGUID = Edge.first.getGUID();
exportGlobalInModule(Index, ExportModulePath, CalleeGUID, ExportList);
}
for (auto &Ref : ResolvedCalleeSummary->refs()) {
auto GUID = Ref.getGUID();
exportGlobalInModule(Index, ExportModulePath, GUID, ExportList);
}
}
}

10
test/ThinLTO/X86/Inputs/export.ll Normal file
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@ -0,0 +1,10 @@
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.11.0"
define i32 @main() #0 {
entry:
call void @callstaticfunc()
ret i32 0
}
declare void @callstaticfunc()

26
test/ThinLTO/X86/export.ll Normal file
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@ -0,0 +1,26 @@
; Do setup work for all below tests: generate bitcode and combined index
; RUN: opt -module-summary %s -o %t1.bc
; RUN: opt -module-summary %p/Inputs/export.ll -o %t2.bc
; RUN: llvm-lto -thinlto-action=thinlink -o %t3.bc %t1.bc %t2.bc
; Ensure statics are promoted/renamed correctly from this file.
; RUN: llvm-lto -thinlto-action=promote %t1.bc -thinlto-index=%t3.bc -o - | llvm-dis -o - | FileCheck %s
; CHECK-DAG: @staticvar.llvm.0 = hidden global
; CHECK-DAG: define hidden void @staticfunc.llvm.0
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.11.0"
@staticvar = internal global i32 1, align 4
define void @callstaticfunc() #0 {
entry:
call void @staticfunc()
ret void
}
define internal void @staticfunc() #0 {
entry:
%0 = load i32, i32* @staticvar, align 4
ret void
}