[llvm] r315136 - [MachineOutliner] Disable outlining from LinkOnceODRs by default
Jessica Paquette via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 6 17:16:35 PDT 2017
Author: paquette
Date: Fri Oct 6 17:16:34 2017
New Revision: 315136
URL: http://llvm.org/viewvc/llvm-project?rev=315136&view=rev
Log:
[MachineOutliner] Disable outlining from LinkOnceODRs by default
Say you have two identical linkonceodr functions, one in M1 and one in M2.
Say that the outliner outlines A,B,C from one function, and D,E,F from another
function (where letters are instructions). Now those functions are not
identical, and cannot be deduped. Locally to M1 and M2, these outlining
choices would be good-- to the whole program, however, this might not be true!
To mitigate this, this commit makes it so that the outliner sees linkonceodr
functions as unsafe to outline from. It also adds a flag,
-enable-linkonceodr-outlining, which allows the user to specify that they
want to outline from such functions when they know what they're doing.
Changing this handles most code size regressions in the test suite caused by
competing with linker dedupe. It also doesn't have a huge impact on the code
size improvements from the outliner. There are 6 tests that regress > 5% from
outlining WITH linkonceodrs to outlining WITHOUT linkonceodrs. Overall, most
tests either improve or are not impacted.
Not outlined vs outlined without linkonceodrs:
https://hastebin.com/raw/qeguxavuda
Not outlined vs outlined with linkonceodrs:
https://hastebin.com/raw/edepoqoqic
Outlined with linkonceodrs vs outlined without linkonceodrs:
https://hastebin.com/raw/awiqifiheb
Numbers generated using compare.py with -m size.__text. Tests run for AArch64
with -Oz -mllvm -enable-machine-outliner -mno-red-zone.
Modified:
llvm/trunk/include/llvm/CodeGen/Passes.h
llvm/trunk/include/llvm/Target/TargetInstrInfo.h
llvm/trunk/lib/CodeGen/MachineOutliner.cpp
llvm/trunk/lib/CodeGen/TargetPassConfig.cpp
llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp
llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.h
llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
llvm/trunk/lib/Target/X86/X86InstrInfo.h
llvm/trunk/test/CodeGen/AArch64/machine-outliner.ll
Modified: llvm/trunk/include/llvm/CodeGen/Passes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/Passes.h?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/Passes.h (original)
+++ llvm/trunk/include/llvm/CodeGen/Passes.h Fri Oct 6 17:16:34 2017
@@ -411,7 +411,7 @@ namespace llvm {
/// This pass performs outlining on machine instructions directly before
/// printing assembly.
- ModulePass *createMachineOutlinerPass();
+ ModulePass *createMachineOutlinerPass(bool OutlineFromLinkOnceODRs = false);
/// This pass expands the experimental reduction intrinsics into sequences of
/// shuffles.
Modified: llvm/trunk/include/llvm/Target/TargetInstrInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetInstrInfo.h?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetInstrInfo.h (original)
+++ llvm/trunk/include/llvm/Target/TargetInstrInfo.h Fri Oct 6 17:16:34 2017
@@ -1646,7 +1646,8 @@ public:
/// A function \p MF is considered safe for outlining if an outlined function
/// produced from instructions in F will produce a program which produces the
/// same output for any set of given inputs.
- virtual bool isFunctionSafeToOutlineFrom(MachineFunction &MF) const {
+ virtual bool isFunctionSafeToOutlineFrom(MachineFunction &MF,
+ bool OutlineFromLinkOnceODRs) const {
llvm_unreachable("Target didn't implement "
"TargetInstrInfo::isFunctionSafeToOutlineFrom!");
}
Modified: llvm/trunk/lib/CodeGen/MachineOutliner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineOutliner.cpp?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineOutliner.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineOutliner.cpp Fri Oct 6 17:16:34 2017
@@ -746,6 +746,10 @@ struct MachineOutliner : public ModulePa
static char ID;
+ /// \brief Set to true if the outliner should consider functions with
+ /// linkonceodr linkage.
+ bool OutlineFromLinkOnceODRs = false;
+
StringRef getPassName() const override { return "Machine Outliner"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
@@ -755,7 +759,8 @@ struct MachineOutliner : public ModulePa
ModulePass::getAnalysisUsage(AU);
}
- MachineOutliner() : ModulePass(ID) {
+ MachineOutliner(bool OutlineFromLinkOnceODRs = false) :
+ ModulePass(ID), OutlineFromLinkOnceODRs(OutlineFromLinkOnceODRs) {
initializeMachineOutlinerPass(*PassRegistry::getPassRegistry());
}
@@ -844,7 +849,10 @@ struct MachineOutliner : public ModulePa
char MachineOutliner::ID = 0;
namespace llvm {
-ModulePass *createMachineOutlinerPass() { return new MachineOutliner(); }
+ModulePass *createMachineOutlinerPass(bool OutlineFromLinkOnceODRs) {
+ return new MachineOutliner(OutlineFromLinkOnceODRs);
+}
+
} // namespace llvm
INITIALIZE_PASS(MachineOutliner, DEBUG_TYPE, "Machine Function Outliner", false,
@@ -1248,7 +1256,8 @@ bool MachineOutliner::runOnModule(Module
MachineFunction &MF = MMI.getOrCreateMachineFunction(F);
// Is the function empty? Safe to outline from?
- if (F.empty() || !TII->isFunctionSafeToOutlineFrom(MF))
+ if (F.empty() ||
+ !TII->isFunctionSafeToOutlineFrom(MF, OutlineFromLinkOnceODRs))
continue;
// If it is, look at each MachineBasicBlock in the function.
Modified: llvm/trunk/lib/CodeGen/TargetPassConfig.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TargetPassConfig.cpp?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TargetPassConfig.cpp (original)
+++ llvm/trunk/lib/CodeGen/TargetPassConfig.cpp Fri Oct 6 17:16:34 2017
@@ -111,6 +111,11 @@ static cl::opt<bool> VerifyMachineCode("
static cl::opt<bool> EnableMachineOutliner("enable-machine-outliner",
cl::Hidden,
cl::desc("Enable machine outliner"));
+static cl::opt<bool> EnableLinkOnceODROutlining(
+ "enable-linkonceodr-outlining",
+ cl::Hidden,
+ cl::desc("Enable the machine outliner on linkonceodr functions"),
+ cl::init(false));
// Enable or disable FastISel. Both options are needed, because
// FastISel is enabled by default with -fast, and we wish to be
// able to enable or disable fast-isel independently from -O0.
@@ -891,7 +896,7 @@ void TargetPassConfig::addMachinePasses(
addPass(&PatchableFunctionID, false);
if (EnableMachineOutliner)
- PM->add(createMachineOutlinerPass());
+ PM->add(createMachineOutlinerPass(EnableLinkOnceODROutlining));
AddingMachinePasses = false;
}
Modified: llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp Fri Oct 6 17:16:34 2017
@@ -4646,13 +4646,24 @@ AArch64InstrInfo::getOutlininingCandidat
FrameID);
}
-bool AArch64InstrInfo::isFunctionSafeToOutlineFrom(MachineFunction &MF) const {
- // If MF has a red zone, then we ought not to outline from it, since outlined
- // functions can modify/read from the stack.
- // If MF's address is taken, then we don't want to outline from it either
- // since we don't really know what the user is doing with it.
- return MF.getFunction()->hasFnAttribute(Attribute::NoRedZone) &&
- !MF.getFunction()->hasAddressTaken();
+bool AArch64InstrInfo::isFunctionSafeToOutlineFrom(MachineFunction &MF,
+ bool OutlineFromLinkOnceODRs) const {
+ const Function *F = MF.getFunction();
+
+ // If F uses a redzone, then don't outline from it because it might mess up
+ // the stack.
+ if (!F->hasFnAttribute(Attribute::NoRedZone))
+ return false;
+
+ // If anyone is using the address of this function, don't outline from it.
+ if (F->hasAddressTaken())
+ return false;
+
+ // Can F be deduplicated by the linker? If it can, don't outline from it.
+ if (!OutlineFromLinkOnceODRs && F->hasLinkOnceODRLinkage())
+ return false;
+
+ return true;
}
AArch64GenInstrInfo::MachineOutlinerInstrType
Modified: llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.h?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.h (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.h Fri Oct 6 17:16:34 2017
@@ -352,7 +352,8 @@ public:
bool
canOutlineWithoutLRSave(MachineBasicBlock::iterator &CallInsertionPt) const;
- bool isFunctionSafeToOutlineFrom(MachineFunction &MF) const override;
+ bool isFunctionSafeToOutlineFrom(MachineFunction &MF,
+ bool OutlineFromLinkOnceODRs) const override;
MachineOutlinerInfo getOutlininingCandidateInfo(
std::vector<
std::pair<MachineBasicBlock::iterator, MachineBasicBlock::iterator>>
Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Fri Oct 6 17:16:34 2017
@@ -10763,8 +10763,22 @@ X86InstrInfo::getOutlininingCandidateInf
MachineOutlinerDefault);
}
-bool X86InstrInfo::isFunctionSafeToOutlineFrom(MachineFunction &MF) const {
- return MF.getFunction()->hasFnAttribute(Attribute::NoRedZone);
+bool X86InstrInfo::isFunctionSafeToOutlineFrom(MachineFunction &MF,
+ bool OutlineFromLinkOnceODRs) const {
+ const Function *F = MF.getFunction();
+
+ // Does the function use a red zone? If it does, then we can't risk messing
+ // with the stack.
+ if (!F->hasFnAttribute(Attribute::NoRedZone))
+ return false;
+
+ // If we *don't* want to outline from things that could potentially be deduped
+ // then return false.
+ if (!OutlineFromLinkOnceODRs && F->hasLinkOnceODRLinkage())
+ return false;
+
+ // This function is viable for outlining, so return true.
+ return true;
}
X86GenInstrInfo::MachineOutlinerInstrType
Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.h?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.h (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.h Fri Oct 6 17:16:34 2017
@@ -564,7 +564,8 @@ public:
std::pair<MachineBasicBlock::iterator, MachineBasicBlock::iterator>>
&RepeatedSequenceLocs) const override;
- bool isFunctionSafeToOutlineFrom(MachineFunction &MF) const override;
+ bool isFunctionSafeToOutlineFrom(MachineFunction &MF,
+ bool OutlineFromLinkOnceODRs) const override;
llvm::X86GenInstrInfo::MachineOutlinerInstrType
getOutliningType(MachineInstr &MI) const override;
Modified: llvm/trunk/test/CodeGen/AArch64/machine-outliner.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/machine-outliner.ll?rev=315136&r1=315135&r2=315136&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/machine-outliner.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/machine-outliner.ll Fri Oct 6 17:16:34 2017
@@ -1,9 +1,31 @@
-; RUN: llc -enable-machine-outliner -mtriple=aarch64-apple-darwin < %s | FileCheck %s
+; RUN: llc -enable-machine-outliner -mtriple=aarch64-apple-darwin < %s | FileCheck %s -check-prefix=NoODR
+; RUN: llc -enable-machine-outliner -enable-linkonceodr-outlining -mtriple=aarch64-apple-darwin < %s | FileCheck %s -check-prefix=ODR
+
+define linkonce_odr void @fish() #0 {
+ ; CHECK-LABEL: _fish:
+ ; NoODR: orr w8, wzr, #0x1
+ ; NoODR-NEXT: stp w8, wzr, [sp, #8]
+ ; NoODR-NEXT: orr w8, wzr, #0x2
+ ; NoODR-NEXT: str w8, [sp, #4]
+ ; NoODR-NEXT: orr w8, wzr, #0x3
+ ; NoODR-NEXT: str w8, [sp], #16
+ ; NoODR-NEXT: ret
+ ; ODR: b l_OUTLINED_FUNCTION_0
+ %1 = alloca i32, align 4
+ %2 = alloca i32, align 4
+ %3 = alloca i32, align 4
+ %4 = alloca i32, align 4
+ store i32 0, i32* %1, align 4
+ store i32 1, i32* %2, align 4
+ store i32 2, i32* %3, align 4
+ store i32 3, i32* %4, align 4
+ ret void
+}
define void @cat() #0 {
-; CHECK-LABEL: _cat:
-; CHECK: b l_OUTLINED_FUNCTION_0
-; CHECK-NOT: ret
+ ; CHECK-LABEL: _cat:
+ ; CHECK: b l_OUTLINED_FUNCTION_0
+ ; CHECK-NOT: ret
%1 = alloca i32, align 4
%2 = alloca i32, align 4
%3 = alloca i32, align 4
@@ -16,9 +38,9 @@ define void @cat() #0 {
}
define void @dog() #0 {
-; CHECK-LABEL: _dog:
-; CHECK: b l_OUTLINED_FUNCTION_0
-; CHECK-NOT: ret
+ ; CHECK-LABEL: _dog:
+ ; CHECK: b l_OUTLINED_FUNCTION_0
+ ; CHECK-NOT: ret
%1 = alloca i32, align 4
%2 = alloca i32, align 4
%3 = alloca i32, align 4
@@ -39,5 +61,4 @@ define void @dog() #0 {
; CHECK-NEXT: str w8, [sp], #16
; CHECK-NEXT: ret
-
attributes #0 = { noredzone nounwind ssp uwtable "no-frame-pointer-elim"="false" "target-cpu"="cyclone" }
More information about the llvm-commits
mailing list