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[ThinLTO] - Fix for "ThinLTO inlines variables that should be discarded".

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This fixes PR36187.

Patch teaches ThinLTO to drop non-prevailing variables, 
just like we recently did for functions (in r323633).

Differential revision: https://reviews.llvm.org/D42798

llvm-svn: 324075
This commit is contained in:
George Rimar 2018-02-02 12:17:33 +00:00
parent e5082955c1
commit dba1b32ded
3 changed files with 50 additions and 7 deletions
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18
lib/LTO/LTOBackend.cpp
View File

@ -401,13 +401,19 @@ Error lto::backend(Config &C, AddStreamFn AddStream,
static void dropDeadSymbols(Module &Mod, const GVSummaryMapTy &DefinedGlobals,
const ModuleSummaryIndex &Index) {
for (auto &GV : Mod) {
auto MaybeDrop = [&](GlobalValue &GV) {
auto It = DefinedGlobals.find(GV.getGUID());
if (It == DefinedGlobals.end())
continue;
if (!Index.isGlobalValueLive(It->second))
convertToDeclaration(GV);
}
if (It != DefinedGlobals.end())
if (!Index.isGlobalValueLive(It->second))
convertToDeclaration(GV);
};
// Process functions and global now.
// FIXME: add support for aliases (needs support in convertToDeclaration).
for (auto &GV : Mod)
MaybeDrop(GV);
for (auto &GV : Mod.globals())
MaybeDrop(GV);
}
Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,

35
test/LTO/Resolution/X86/not-prevailing-variables.ll Normal file
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@ -0,0 +1,35 @@
; RUN: opt -module-summary %s -o %t1.o
; RUN: llvm-lto2 run -save-temps -o %t2.o %t1.o \
; RUN: -r %t1.o,testVar1,plx -r %t1.o,testVar2,plx \
; RUN: -r %t1.o,var1,pl -r %t1.o,var2,lx
; Test contains two variables: var1 and var2.
; var2 is not prevailing and here we check it is not inlined.
; Check 'var2' was not inlined.
; RUN: llvm-objdump -d %t2.o.1 | FileCheck %s
; CHECK: testVar1:
; CHECK-NEXT: movl $10, %eax
; CHECK-NEXT: retq
; CHECK: testVar2:
; CHECK-NEXT: movl (%rip), %eax
; CHECK-NEXT: retq
; Check 'var2' is undefined.
; RUN: llvm-readelf --symbols %t2.o.1 | FileCheck %s --check-prefix=UND
; UND: NOTYPE GLOBAL DEFAULT UND var2
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@var1 = global i32 10, align 4
define i32 @testVar1() {
%1 = load i32, i32* @var1, align 4
ret i32 %1
}
@var2 = global i32 11, align 4
define i32 @testVar2() {
%1 = load i32, i32* @var2, align 4
ret i32 %1
}

4
test/tools/gold/X86/global_with_section.ll
View File

@ -45,7 +45,9 @@ target triple = "x86_64-unknown-linux-gnu"
; Confirm via a variable with a non-C identifier section that we are getting
; the expected internalization.
; CHECK-DAG: @var_with_nonC_section = internal global i32 0, section ".nonCsection"
; CHECK-REGULARLTO-DAG: @var_with_nonC_section = internal global i32 0, section ".nonCsection"
; Check we dropped definition of dead variable.
; CHECK-THINLTO-DAG: @var_with_nonC_section = external dso_local global i32, section ".nonCsection"
@var_with_nonC_section = global i32 0, section ".nonCsection"
; We should not internalize @deadfunc_with_section due to section