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[CodeExtractor] Only lift lifetime markers present in the extraction region 

When CodeExtractor finds liftime markers referencing inputs to the
extraction region, it lifts these markers out of the region and inserts
them around the call to the extracted function (see r350420, PR39671).

However, it should *only* lift lifetime markers that are actually
present in the extraction region. I.e., if a start marker is present in
the extraction region but a corresponding end marker isn't (or vice
versa), only the start marker (or end marker, resp.) should be lifted.

Differential Revision: https://reviews.llvm.org/D57834

llvm-svn: 353973
This commit is contained in:
Vedant Kumar 2019-02-13 19:53:38 +00:00
parent 9fc51bae73
commit 4b0cc9a7c8
3 changed files with 194 additions and 37 deletions
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96
llvm/lib/Transforms/Utils/CodeExtractor.cpp
View File

@ -885,16 +885,17 @@ Function *CodeExtractor::constructFunction(const ValueSet &inputs,
return newFunction;
}
/// Scan the extraction region for lifetime markers which reference inputs.
/// Erase these markers. Return the inputs which were referenced.
/// Erase lifetime.start markers which reference inputs to the extraction
/// region, and insert the referenced memory into \p LifetimesStart. Do the same
/// with lifetime.end markers (but insert them into \p LifetimesEnd).
///
/// The extraction region is defined by a set of blocks (\p Blocks), and a set
/// of allocas which will be moved from the caller function into the extracted
/// function (\p SunkAllocas).
static SetVector<Value *>
eraseLifetimeMarkersOnInputs(const SetVector<BasicBlock *> &Blocks,
const SetVector<Value *> &SunkAllocas) {
SetVector<Value *> InputObjectsWithLifetime;
static void eraseLifetimeMarkersOnInputs(const SetVector<BasicBlock *> &Blocks,
const SetVector<Value *> &SunkAllocas,
SetVector<Value *> &LifetimesStart,
SetVector<Value *> &LifetimesEnd) {
for (BasicBlock *BB : Blocks) {
for (auto It = BB->begin(), End = BB->end(); It != End;) {
auto *II = dyn_cast<IntrinsicInst>(&*It);
@ -909,44 +910,64 @@ eraseLifetimeMarkersOnInputs(const SetVector<BasicBlock *> &Blocks,
if (SunkAllocas.count(Mem) || definedInRegion(Blocks, Mem))
continue;
InputObjectsWithLifetime.insert(Mem);
if (II->getIntrinsicID() == Intrinsic::lifetime_start)
LifetimesStart.insert(Mem);
else
LifetimesEnd.insert(Mem);
II->eraseFromParent();
}
}
return InputObjectsWithLifetime;
}
/// Insert lifetime start/end markers surrounding the call to the new function
/// for objects defined in the caller.
static void insertLifetimeMarkersSurroundingCall(Module *M,
ArrayRef<Value *> Objects,
CallInst *TheCall) {
if (Objects.empty())
return;
static void insertLifetimeMarkersSurroundingCall(
Module *M, ArrayRef<Value *> LifetimesStart, ArrayRef<Value *> LifetimesEnd,
CallInst *TheCall) {
LLVMContext &Ctx = M->getContext();
auto Int8PtrTy = Type::getInt8PtrTy(Ctx);
auto NegativeOne = ConstantInt::getSigned(Type::getInt64Ty(Ctx), -1);
auto StartFn = llvm::Intrinsic::getDeclaration(
M, llvm::Intrinsic::lifetime_start, Int8PtrTy);
auto EndFn = llvm::Intrinsic::getDeclaration(M, llvm::Intrinsic::lifetime_end,
Int8PtrTy);
Instruction *Term = TheCall->getParent()->getTerminator();
for (Value *Mem : Objects) {
assert((!isa<Instruction>(Mem) ||
cast<Instruction>(Mem)->getFunction() == TheCall->getFunction()) &&
"Input memory not defined in original function");
Value *MemAsI8Ptr = nullptr;
if (Mem->getType() == Int8PtrTy)
MemAsI8Ptr = Mem;
else
MemAsI8Ptr =
CastInst::CreatePointerCast(Mem, Int8PtrTy, "lt.cast", TheCall);
auto StartMarker = CallInst::Create(StartFn, {NegativeOne, MemAsI8Ptr});
StartMarker->insertBefore(TheCall);
auto EndMarker = CallInst::Create(EndFn, {NegativeOne, MemAsI8Ptr});
EndMarker->insertBefore(Term);
// The memory argument to a lifetime marker must be a i8*. Cache any bitcasts
// needed to satisfy this requirement so they may be reused.
DenseMap<Value *, Value *> Bitcasts;
// Emit lifetime markers for the pointers given in \p Objects. Insert the
// markers before the call if \p InsertBefore, and after the call otherwise.
auto insertMarkers = [&](Function *MarkerFunc, ArrayRef<Value *> Objects,
bool InsertBefore) {
for (Value *Mem : Objects) {
assert((!isa<Instruction>(Mem) || cast<Instruction>(Mem)->getFunction() ==
TheCall->getFunction()) &&
"Input memory not defined in original function");
Value *&MemAsI8Ptr = Bitcasts[Mem];
if (!MemAsI8Ptr) {
if (Mem->getType() == Int8PtrTy)
MemAsI8Ptr = Mem;
else
MemAsI8Ptr =
CastInst::CreatePointerCast(Mem, Int8PtrTy, "lt.cast", TheCall);
}
auto Marker = CallInst::Create(MarkerFunc, {NegativeOne, MemAsI8Ptr});
if (InsertBefore)
Marker->insertBefore(TheCall);
else
Marker->insertBefore(Term);
}
};
if (!LifetimesStart.empty()) {
auto StartFn = llvm::Intrinsic::getDeclaration(
M, llvm::Intrinsic::lifetime_start, Int8PtrTy);
insertMarkers(StartFn, LifetimesStart, /*InsertBefore=*/true);
}
if (!LifetimesEnd.empty()) {
auto EndFn = llvm::Intrinsic::getDeclaration(
M, llvm::Intrinsic::lifetime_end, Int8PtrTy);
insertMarkers(EndFn, LifetimesEnd, /*InsertBefore=*/false);
}
}
@ -1214,7 +1235,7 @@ CallInst *CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
// Insert lifetime markers around the reloads of any output values. The
// allocas output values are stored in are only in-use in the codeRepl block.
insertLifetimeMarkersSurroundingCall(M, ReloadOutputs, call);
insertLifetimeMarkersSurroundingCall(M, ReloadOutputs, ReloadOutputs, call);
return call;
}
@ -1403,8 +1424,9 @@ Function *CodeExtractor::extractCodeRegion() {
// referenced by lifetime start/end markers within it. The effects of these
// markers must be replicated in the calling function to prevent the stack
// coloring pass from merging slots which store input objects.
ValueSet InputObjectsWithLifetime =
eraseLifetimeMarkersOnInputs(Blocks, SinkingCands);
ValueSet LifetimesStart, LifetimesEnd;
eraseLifetimeMarkersOnInputs(Blocks, SinkingCands, LifetimesStart,
LifetimesEnd);
// Construct new function based on inputs/outputs & add allocas for all defs.
Function *newFunction =
@ -1428,8 +1450,8 @@ Function *CodeExtractor::extractCodeRegion() {
// Replicate the effects of any lifetime start/end markers which referenced
// input objects in the extraction region by placing markers around the call.
insertLifetimeMarkersSurroundingCall(oldFunction->getParent(),
InputObjectsWithLifetime.getArrayRef(),
TheCall);
LifetimesStart.getArrayRef(),
LifetimesEnd.getArrayRef(), TheCall);
// Propagate personality info to the new function if there is one.
if (oldFunction->hasPersonalityFn())

0
llvm/test/Transforms/HotColdSplit/lifetime-markers-on-inputs.ll → llvm/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-1.ll
View File

135
llvm/test/Transforms/HotColdSplit/lifetime-markers-on-inputs-2.ll Normal file
View File

@ -0,0 +1,135 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -hotcoldsplit -hotcoldsplit-threshold=0 < %s 2>&1 | FileCheck %s
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
declare void @cold_use(i8*) cold
; In this CFG, splitting will extract the blocks extract{1,2}. I.e., it will
; extract a lifetime.start marker, but not the corresponding lifetime.end
; marker. Make sure that a lifetime.start marker is emitted before the call to
; the split function, and *only* that marker.
;
; entry
; / \
; extract1 no-extract1
; (lt.start) |
; / |
; extract2 |
; \_____ |
; \ /
; exit
; (lt.end)
;
; After splitting, we should see:
;
; entry
; / \
; codeRepl no-extract1
; (lt.start) |
; \ /
; exit
; (lt.end)
define void @only_lifetime_start_is_cold() {
; CHECK-LABEL: @only_lifetime_start_is_cold(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[LOCAL1:%.*]] = alloca i256
; CHECK-NEXT: [[LOCAL1_CAST:%.*]] = bitcast i256* [[LOCAL1]] to i8*
; CHECK-NEXT: br i1 undef, label [[CODEREPL:%.*]], label [[NO_EXTRACT1:%.*]]
; CHECK: codeRepl:
; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i256* [[LOCAL1]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 -1, i8* [[LT_CAST]])
; CHECK-NEXT: [[TARGETBLOCK:%.*]] = call i1 @only_lifetime_start_is_cold.cold.1(i8* [[LOCAL1_CAST]]) #3
; CHECK-NEXT: br i1 [[TARGETBLOCK]], label [[NO_EXTRACT1]], label [[EXIT:%.*]]
; CHECK: no-extract1:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 1, i8* [[LOCAL1_CAST]])
; CHECK-NEXT: ret void
;
entry:
%local1 = alloca i256
%local1_cast = bitcast i256* %local1 to i8*
br i1 undef, label %extract1, label %no-extract1
extract1:
; lt.start
call void @llvm.lifetime.start.p0i8(i64 1, i8* %local1_cast)
call void @cold_use(i8* %local1_cast)
br i1 undef, label %extract2, label %no-extract1
extract2:
br label %exit
no-extract1:
br label %exit
exit:
; lt.end
call void @llvm.lifetime.end.p0i8(i64 1, i8* %local1_cast)
ret void
}
; In this CFG, splitting will extract the block extract1. I.e., it will extract
; a lifetime.end marker, but not the corresponding lifetime.start marker. Make
; sure that a lifetime.end marker is emitted after the call to the split
; function, and *only* that marker.
;
; entry
; (lt.start)
; / \
; no-extract1 extract1
; (lt.end) (lt.end)
; \ /
; exit
;
; After splitting, we should see:
;
; entry
; (lt.start)
; / \
; no-extract1 codeRepl
; (lt.end) (lt.end)
; \ /
; exit
define void @only_lifetime_end_is_cold() {
; CHECK-LABEL: @only_lifetime_end_is_cold(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[LOCAL1:%.*]] = alloca i256
; CHECK-NEXT: [[LOCAL1_CAST:%.*]] = bitcast i256* [[LOCAL1]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 1, i8* [[LOCAL1_CAST]])
; CHECK-NEXT: br i1 undef, label [[NO_EXTRACT1:%.*]], label [[CODEREPL:%.*]]
; CHECK: no-extract1:
; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 1, i8* [[LOCAL1_CAST]])
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: codeRepl:
; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i256* [[LOCAL1]] to i8*
; CHECK-NEXT: call void @only_lifetime_end_is_cold.cold.1(i8* [[LOCAL1_CAST]]) #3
; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[LT_CAST]])
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
; lt.start
%local1 = alloca i256
%local1_cast = bitcast i256* %local1 to i8*
call void @llvm.lifetime.start.p0i8(i64 1, i8* %local1_cast)
br i1 undef, label %no-extract1, label %extract1
no-extract1:
; lt.end
call void @llvm.lifetime.end.p0i8(i64 1, i8* %local1_cast)
br label %exit
extract1:
; lt.end
call void @cold_use(i8* %local1_cast)
call void @llvm.lifetime.end.p0i8(i64 1, i8* %local1_cast)
br label %exit
exit:
ret void
}