[llvm] r287178 - Introduce GlobalSplit pass.
Peter Collingbourne via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 16 15:40:26 PST 2016
Author: pcc
Date: Wed Nov 16 17:40:26 2016
New Revision: 287178
URL: http://llvm.org/viewvc/llvm-project?rev=287178&view=rev
Log:
Introduce GlobalSplit pass.
This pass splits globals into elements using inrange annotations on
getelementptr indices.
Differential Revision: https://reviews.llvm.org/D22295
Added:
llvm/trunk/lib/Transforms/IPO/GlobalSplit.cpp
llvm/trunk/test/Transforms/GlobalSplit/
llvm/trunk/test/Transforms/GlobalSplit/basic.ll
llvm/trunk/test/Transforms/GlobalSplit/non-beneficial.ll
llvm/trunk/test/Transforms/GlobalSplit/nonlocal.ll
Modified:
llvm/trunk/include/llvm/InitializePasses.h
llvm/trunk/include/llvm/Transforms/IPO.h
llvm/trunk/lib/Transforms/IPO/CMakeLists.txt
llvm/trunk/lib/Transforms/IPO/IPO.cpp
llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
Modified: llvm/trunk/include/llvm/InitializePasses.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/InitializePasses.h?rev=287178&r1=287177&r2=287178&view=diff
==============================================================================
--- llvm/trunk/include/llvm/InitializePasses.h (original)
+++ llvm/trunk/include/llvm/InitializePasses.h Wed Nov 16 17:40:26 2016
@@ -145,6 +145,7 @@ void initializeGVNLegacyPassPass(PassReg
void initializeGlobalDCELegacyPassPass(PassRegistry&);
void initializeGlobalMergePass(PassRegistry&);
void initializeGlobalOptLegacyPassPass(PassRegistry&);
+void initializeGlobalSplitPass(PassRegistry&);
void initializeGlobalsAAWrapperPassPass(PassRegistry&);
void initializeGuardWideningLegacyPassPass(PassRegistry&);
void initializeIPCPPass(PassRegistry&);
Modified: llvm/trunk/include/llvm/Transforms/IPO.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/IPO.h?rev=287178&r1=287177&r2=287178&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/IPO.h (original)
+++ llvm/trunk/include/llvm/Transforms/IPO.h Wed Nov 16 17:40:26 2016
@@ -225,6 +225,10 @@ ModulePass *createCrossDSOCFIPass();
/// metadata.
ModulePass *createWholeProgramDevirtPass();
+/// This pass splits globals into pieces for the benefit of whole-program
+/// devirtualization and control-flow integrity.
+ModulePass *createGlobalSplitPass();
+
//===----------------------------------------------------------------------===//
// SampleProfilePass - Loads sample profile data from disk and generates
// IR metadata to reflect the profile.
Modified: llvm/trunk/lib/Transforms/IPO/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/CMakeLists.txt?rev=287178&r1=287177&r2=287178&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/CMakeLists.txt (original)
+++ llvm/trunk/lib/Transforms/IPO/CMakeLists.txt Wed Nov 16 17:40:26 2016
@@ -12,6 +12,7 @@ add_llvm_library(LLVMipo
FunctionImport.cpp
GlobalDCE.cpp
GlobalOpt.cpp
+ GlobalSplit.cpp
IPConstantPropagation.cpp
IPO.cpp
InferFunctionAttrs.cpp
Added: llvm/trunk/lib/Transforms/IPO/GlobalSplit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalSplit.cpp?rev=287178&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalSplit.cpp (added)
+++ llvm/trunk/lib/Transforms/IPO/GlobalSplit.cpp Wed Nov 16 17:40:26 2016
@@ -0,0 +1,164 @@
+//===- GlobalSplit.cpp - global variable splitter -------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass uses inrange annotations on GEP indices to split globals where
+// beneficial. Clang currently attaches these annotations to references to
+// virtual table globals under the Itanium ABI for the benefit of the
+// whole-program virtual call optimization and control flow integrity passes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/Pass.h"
+
+#include <set>
+
+using namespace llvm;
+
+namespace {
+
+bool splitGlobal(GlobalVariable &GV) {
+ // If the address of the global is taken outside of the module, we cannot
+ // apply this transformation.
+ if (!GV.hasLocalLinkage())
+ return false;
+
+ // We currently only know how to split ConstantStructs.
+ auto *Init = dyn_cast_or_null<ConstantStruct>(GV.getInitializer());
+ if (!Init)
+ return false;
+
+ // Verify that each user of the global is an inrange getelementptr constant.
+ // From this it follows that any loads from or stores to that global must use
+ // a pointer derived from an inrange getelementptr constant, which is
+ // sufficient to allow us to apply the splitting transform.
+ for (User *U : GV.users()) {
+ if (!isa<Constant>(U))
+ return false;
+
+ auto *GEP = dyn_cast<GEPOperator>(U);
+ if (!GEP || !GEP->getInRangeIndex() || *GEP->getInRangeIndex() != 1 ||
+ !isa<ConstantInt>(GEP->getOperand(1)) ||
+ !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
+ !isa<ConstantInt>(GEP->getOperand(2)))
+ return false;
+ }
+
+ SmallVector<MDNode *, 2> Types;
+ GV.getMetadata(LLVMContext::MD_type, Types);
+
+ const DataLayout &DL = GV.getParent()->getDataLayout();
+ const StructLayout *SL = DL.getStructLayout(Init->getType());
+
+ IntegerType *Int32Ty = Type::getInt32Ty(GV.getContext());
+
+ std::vector<GlobalVariable *> SplitGlobals(Init->getNumOperands());
+ for (unsigned I = 0; I != Init->getNumOperands(); ++I) {
+ // Build a global representing this split piece.
+ auto *SplitGV =
+ new GlobalVariable(*GV.getParent(), Init->getOperand(I)->getType(),
+ GV.isConstant(), GlobalValue::PrivateLinkage,
+ Init->getOperand(I), GV.getName() + "." + utostr(I));
+ SplitGlobals[I] = SplitGV;
+
+ unsigned SplitBegin = SL->getElementOffset(I);
+ unsigned SplitEnd = (I == Init->getNumOperands() - 1)
+ ? SL->getSizeInBytes()
+ : SL->getElementOffset(I + 1);
+
+ // Rebuild type metadata, adjusting by the split offset.
+ // FIXME: See if we can use DW_OP_piece to preserve debug metadata here.
+ for (MDNode *Type : Types) {
+ uint64_t ByteOffset = cast<ConstantInt>(
+ cast<ConstantAsMetadata>(Type->getOperand(0))->getValue())
+ ->getZExtValue();
+ if (ByteOffset < SplitBegin || ByteOffset >= SplitEnd)
+ continue;
+ SplitGV->addMetadata(
+ LLVMContext::MD_type,
+ *MDNode::get(GV.getContext(),
+ {ConstantAsMetadata::get(
+ ConstantInt::get(Int32Ty, ByteOffset - SplitBegin)),
+ Type->getOperand(1)}));
+ }
+ }
+
+ for (User *U : GV.users()) {
+ auto *GEP = cast<GEPOperator>(U);
+ unsigned I = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
+ if (I >= SplitGlobals.size())
+ continue;
+
+ SmallVector<Value *, 4> Ops;
+ Ops.push_back(ConstantInt::get(Int32Ty, 0));
+ for (unsigned I = 3; I != GEP->getNumOperands(); ++I)
+ Ops.push_back(GEP->getOperand(I));
+
+ auto *NewGEP = ConstantExpr::getGetElementPtr(
+ SplitGlobals[I]->getInitializer()->getType(), SplitGlobals[I], Ops,
+ GEP->isInBounds());
+ GEP->replaceAllUsesWith(NewGEP);
+ }
+
+ // Finally, remove the original global. Any remaining uses refer to invalid
+ // elements of the global, so replace with undef.
+ if (!GV.use_empty())
+ GV.replaceAllUsesWith(UndefValue::get(GV.getType()));
+ GV.eraseFromParent();
+ return true;
+}
+
+bool splitGlobals(Module &M) {
+ // First, see if the module uses either of the llvm.type.test or
+ // llvm.type.checked.load intrinsics, which indicates that splitting globals
+ // may be beneficial.
+ Function *TypeTestFunc =
+ M.getFunction(Intrinsic::getName(Intrinsic::type_test));
+ Function *TypeCheckedLoadFunc =
+ M.getFunction(Intrinsic::getName(Intrinsic::type_checked_load));
+ if ((!TypeTestFunc || TypeTestFunc->use_empty()) &&
+ (!TypeCheckedLoadFunc || TypeCheckedLoadFunc->use_empty()))
+ return false;
+
+ bool Changed = false;
+ for (auto I = M.global_begin(); I != M.global_end();) {
+ GlobalVariable &GV = *I;
+ ++I;
+ Changed |= splitGlobal(GV);
+ }
+ return Changed;
+}
+
+struct GlobalSplit : public ModulePass {
+ static char ID;
+ GlobalSplit() : ModulePass(ID) {
+ initializeGlobalSplitPass(*PassRegistry::getPassRegistry());
+ }
+ bool runOnModule(Module &M) {
+ if (skipModule(M))
+ return false;
+
+ return splitGlobals(M);
+ }
+};
+
+}
+
+INITIALIZE_PASS(GlobalSplit, "globalsplit", "Global splitter", false, false)
+char GlobalSplit::ID = 0;
+
+ModulePass *llvm::createGlobalSplitPass() {
+ return new GlobalSplit;
+}
Modified: llvm/trunk/lib/Transforms/IPO/IPO.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/IPO.cpp?rev=287178&r1=287177&r2=287178&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/IPO.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/IPO.cpp Wed Nov 16 17:40:26 2016
@@ -32,6 +32,7 @@ void llvm::initializeIPO(PassRegistry &R
initializeForceFunctionAttrsLegacyPassPass(Registry);
initializeGlobalDCELegacyPassPass(Registry);
initializeGlobalOptLegacyPassPass(Registry);
+ initializeGlobalSplitPass(Registry);
initializeIPCPPass(Registry);
initializeAlwaysInlinerLegacyPassPass(Registry);
initializeSimpleInlinerPass(Registry);
Modified: llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp?rev=287178&r1=287177&r2=287178&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp Wed Nov 16 17:40:26 2016
@@ -692,6 +692,11 @@ void PassManagerBuilder::addLTOOptimizat
PM.add(createPostOrderFunctionAttrsLegacyPass());
PM.add(createReversePostOrderFunctionAttrsPass());
+ // Split globals using inrange annotations on GEP indices. This can help
+ // improve the quality of generated code when virtual constant propagation or
+ // control flow integrity are enabled.
+ PM.add(createGlobalSplitPass());
+
// Apply whole-program devirtualization and virtual constant propagation.
PM.add(createWholeProgramDevirtPass());
Added: llvm/trunk/test/Transforms/GlobalSplit/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalSplit/basic.ll?rev=287178&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GlobalSplit/basic.ll (added)
+++ llvm/trunk/test/Transforms/GlobalSplit/basic.ll Wed Nov 16 17:40:26 2016
@@ -0,0 +1,56 @@
+; RUN: opt -S -globalsplit %s | FileCheck %s
+
+target datalayout = "e-p:64:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: @vtt = constant [3 x i8*] [i8* bitcast ([2 x i8* ()*]* @global.0 to i8*), i8* bitcast (i8* ()** getelementptr inbounds ([2 x i8* ()*], [2 x i8* ()*]* @global.0, i32 0, i32 1) to i8*), i8* bitcast ([1 x i8* ()*]* @global.1 to i8*)]
+ at vtt = constant [3 x i8*] [
+ i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 0) to i8*),
+ i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 1) to i8*),
+ i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 1, i32 0) to i8*)
+]
+
+; CHECK-NOT: @global =
+; CHECK: @global.0 = private constant [2 x i8* ()*] [i8* ()* @f1, i8* ()* @f2], !type [[T1:![0-9]+$]]
+; CHECK: @global.1 = private constant [1 x i8* ()*] [i8* ()* @f3], !type [[T2:![0-9]+$]]
+; CHECK-NOT: @global =
+ at global = internal constant { [2 x i8* ()*], [1 x i8* ()*] } {
+ [2 x i8* ()*] [i8* ()* @f1, i8* ()* @f2],
+ [1 x i8* ()*] [i8* ()* @f3]
+}, !type !0, !type !1
+
+; CHECK: define i8* @f1()
+define i8* @f1() {
+ ; CHECK-NEXT: ret i8* bitcast ([2 x i8* ()*]* @global.0 to i8*)
+ ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 0) to i8*)
+}
+
+; CHECK: define i8* @f2()
+define i8* @f2() {
+ ; CHECK-NEXT: ret i8* bitcast (i8* ()** getelementptr inbounds ([2 x i8* ()*], [2 x i8* ()*]* @global.0, i32 0, i32 1) to i8*)
+ ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 1) to i8*)
+}
+
+; CHECK: define i8* @f3()
+define i8* @f3() {
+ ; CHECK-NEXT: ret i8* bitcast (i8* ()** getelementptr inbounds ([2 x i8* ()*], [2 x i8* ()*]* @global.0, i64 1, i32 0) to i8*)
+ ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 2) to i8*)
+}
+
+; CHECK: define i8* @f4()
+define i8* @f4() {
+ ; CHECK-NEXT: ret i8* bitcast ([1 x i8* ()*]* @global.1 to i8*)
+ ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 1, i32 0) to i8*)
+}
+
+define void @foo() {
+ %p = call i1 @llvm.type.test(i8* null, metadata !"")
+ ret void
+}
+
+declare i1 @llvm.type.test(i8*, metadata) nounwind readnone
+
+; CHECK: [[T1]] = !{i32 8, !"foo"}
+; CHECK: [[T2]] = !{i32 0, !"bar"}
+!0 = !{i32 8, !"foo"}
+!1 = !{i32 16, !"bar"}
Added: llvm/trunk/test/Transforms/GlobalSplit/non-beneficial.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalSplit/non-beneficial.ll?rev=287178&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GlobalSplit/non-beneficial.ll (added)
+++ llvm/trunk/test/Transforms/GlobalSplit/non-beneficial.ll Wed Nov 16 17:40:26 2016
@@ -0,0 +1,24 @@
+; RUN: opt -S -globalsplit %s | FileCheck %s
+
+target datalayout = "e-p:64:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: @global =
+ at global = internal constant { [2 x i8* ()*], [1 x i8* ()*] } {
+ [2 x i8* ()*] [i8* ()* @f, i8* ()* @g],
+ [1 x i8* ()*] [i8* ()* @h]
+}
+
+define i8* @f() {
+ ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 0) to i8*)
+}
+
+define i8* @g() {
+ ret i8* null
+}
+
+define i8* @h() {
+ ret i8* null
+}
+
+!0 = !{i32 16}
Added: llvm/trunk/test/Transforms/GlobalSplit/nonlocal.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalSplit/nonlocal.ll?rev=287178&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GlobalSplit/nonlocal.ll (added)
+++ llvm/trunk/test/Transforms/GlobalSplit/nonlocal.ll Wed Nov 16 17:40:26 2016
@@ -0,0 +1,29 @@
+; RUN: opt -S -globalsplit %s | FileCheck %s
+
+target datalayout = "e-p:64:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK: @global =
+ at global = constant { [2 x i8* ()*], [1 x i8* ()*] } {
+ [2 x i8* ()*] [i8* ()* @f, i8* ()* @g],
+ [1 x i8* ()*] [i8* ()* @h]
+}
+
+define i8* @f() {
+ ret i8* bitcast (i8* ()** getelementptr ({ [2 x i8* ()*], [1 x i8* ()*] }, { [2 x i8* ()*], [1 x i8* ()*] }* @global, i32 0, inrange i32 0, i32 0) to i8*)
+}
+
+define i8* @g() {
+ ret i8* null
+}
+
+define i8* @h() {
+ ret i8* null
+}
+
+define void @foo() {
+ %p = call i1 @llvm.type.test(i8* null, metadata !"")
+ ret void
+}
+
+declare i1 @llvm.type.test(i8*, metadata) nounwind readnone
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