Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Allow GC on the first instruction of NoGC region (except in prologs/epilogs) #103540

Merged
merged 7 commits into from
Jun 24, 2024
Merged

Allow GC on the first instruction of NoGC region (except in prologs/epilogs) #103540

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
2a7c328
x64
VSadov Jun 16, 2024
6f726d6
other platforms
VSadov Jun 16, 2024
42a209c
no GC in epilogs
VSadov Jun 16, 2024
7b4feaf
missing change for arm32
VSadov Jun 18, 2024
57591c8
add asserts
VSadov Jun 18, 2024
ff4f223
Addressing PR feedback.
VSadov Jun 24, 2024
bdb38f9
whitespace formatting
VSadov Jun 24, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 5 additions & 5 deletions src/coreclr/jit/codegenarm.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -119,12 +119,12 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
assert(block->KindIs(BBJ_CALLFINALLY));

GetEmitter()->emitIns_J(INS_bl, block->GetTarget());

BasicBlock* nextBlock = block->Next();

if (block->HasFlag(BBF_RETLESS_CALL))
{
GetEmitter()->emitIns_J(INS_bl, block->GetTarget());
Copy link
Member Author

@VSadov VSadov Jun 19, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Unlike other uses of NoGC regions, the use in genCallFinally was starting the NoGC region on instruction after the one that makes GC unsafe.

We need to agree on the same semantics for all the uses, so genCallFinally had to be adjusted to work the same as in other uses of NoGC like block copying, tailcall arg setups,...

Copy link
Member Author

@VSadov VSadov Jun 19, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We could have it the other way (and adjust uses in block copying, etc..), we just need to have it the same way in all cases.

However, starting NoGC region on an instruction group that will make GC unsafe seems a lot more convenient as we may want to start NoGC region before we know exact instructions that will go into it.


if ((nextBlock == nullptr) || !BasicBlock::sameEHRegion(block, nextBlock))
{
instGen(INS_BREAKPOINT);
Expand All @@ -138,12 +138,12 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)

// Because of the way the flowgraph is connected, the liveness info for this one instruction
// after the call is not (can not be) correct in cases where a variable has a last use in the
// handler. So turn off GC reporting for this single instruction.
// handler. So turn off GC reporting once we execute the call and reenable after the jmp/nop
GetEmitter()->emitDisableGC();

BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
GetEmitter()->emitIns_J(INS_bl, block->GetTarget());

// Now go to where the finally funclet needs to return to.
BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
if (nextBlock->NextIs(finallyContinuation) && !compiler->fgInDifferentRegions(nextBlock, finallyContinuation))
{
// Fall-through.
Expand Down
13 changes: 7 additions & 6 deletions src/coreclr/jit/codegenarm64.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2146,6 +2146,8 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
assert(block->KindIs(BBJ_CALLFINALLY));

BasicBlock* const nextBlock = block->Next();

// Generate a call to the finally, like this:
// mov x0,qword ptr [fp + 10H] / sp // Load x0 with PSPSym, or sp if PSPSym is not used
// bl finally-funclet
Expand All @@ -2160,12 +2162,11 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
GetEmitter()->emitIns_Mov(INS_mov, EA_PTRSIZE, REG_R0, REG_SPBASE, /* canSkip */ false);
}
GetEmitter()->emitIns_J(INS_bl_local, block->GetTarget());

BasicBlock* const nextBlock = block->Next();

if (block->HasFlag(BBF_RETLESS_CALL))
{
GetEmitter()->emitIns_J(INS_bl_local, block->GetTarget());

// We have a retless call, and the last instruction generated was a call.
// If the next block is in a different EH region (or is the end of the code
// block), then we need to generate a breakpoint here (since it will never
Expand All @@ -2182,12 +2183,12 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
// Because of the way the flowgraph is connected, the liveness info for this one instruction
// after the call is not (can not be) correct in cases where a variable has a last use in the
// handler. So turn off GC reporting for this single instruction.
// handler. So turn off GC reporting once we execute the call and reenable after the jmp/nop
GetEmitter()->emitDisableGC();

BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
GetEmitter()->emitIns_J(INS_bl_local, block->GetTarget());

// Now go to where the finally funclet needs to return to.
BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
if (nextBlock->NextIs(finallyContinuation) && !compiler->fgInDifferentRegions(nextBlock, finallyContinuation))
{
// Fall-through.
Expand Down
13 changes: 7 additions & 6 deletions src/coreclr/jit/codegenloongarch64.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1368,6 +1368,8 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
assert(block->KindIs(BBJ_CALLFINALLY));

BasicBlock* const nextBlock = block->Next();

// Generate a call to the finally, like this:
// mov a0,qword ptr [fp + 10H] / sp // Load a0 with PSPSym, or sp if PSPSym is not used
// bl finally-funclet
Expand All @@ -1382,12 +1384,11 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
GetEmitter()->emitIns_R_R_I(INS_ori, EA_PTRSIZE, REG_A0, REG_SPBASE, 0);
}
GetEmitter()->emitIns_J(INS_bl, block->GetTarget());

BasicBlock* const nextBlock = block->Next();

if (block->HasFlag(BBF_RETLESS_CALL))
{
GetEmitter()->emitIns_J(INS_bl, block->GetTarget());

// We have a retless call, and the last instruction generated was a call.
// If the next block is in a different EH region (or is the end of the code
// block), then we need to generate a breakpoint here (since it will never
Expand All @@ -1404,12 +1405,12 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
// Because of the way the flowgraph is connected, the liveness info for this one instruction
// after the call is not (can not be) correct in cases where a variable has a last use in the
// handler. So turn off GC reporting for this single instruction.
// handler. So turn off GC reporting once we execute the call and reenable after the jmp/nop
GetEmitter()->emitDisableGC();

BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
GetEmitter()->emitIns_J(INS_bl, block->GetTarget());

// Now go to where the finally funclet needs to return to.
BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
if (nextBlock->NextIs(finallyContinuation) && !compiler->fgInDifferentRegions(nextBlock, finallyContinuation))
{
// Fall-through.
Expand Down
13 changes: 7 additions & 6 deletions src/coreclr/jit/codegenriscv64.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1397,6 +1397,8 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
assert(block->KindIs(BBJ_CALLFINALLY));

BasicBlock* const nextBlock = block->Next();

// Generate a call to the finally, like this:
// mov a0,qword ptr [fp + 10H] / sp // Load a0 with PSPSym, or sp if PSPSym is not used
// jal finally-funclet
Expand All @@ -1411,12 +1413,11 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
GetEmitter()->emitIns_R_R_I(INS_ori, EA_PTRSIZE, REG_A0, REG_SPBASE, 0);
}
GetEmitter()->emitIns_J(INS_jal, block->GetTarget());

BasicBlock* const nextBlock = block->Next();

if (block->HasFlag(BBF_RETLESS_CALL))
{
GetEmitter()->emitIns_J(INS_jal, block->GetTarget());

// We have a retless call, and the last instruction generated was a call.
// If the next block is in a different EH region (or is the end of the code
// block), then we need to generate a breakpoint here (since it will never
Expand All @@ -1433,12 +1434,12 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
// Because of the way the flowgraph is connected, the liveness info for this one instruction
// after the call is not (can not be) correct in cases where a variable has a last use in the
// handler. So turn off GC reporting for this single instruction.
// handler. So turn off GC reporting once we execute the call and reenable after the jmp/nop
GetEmitter()->emitDisableGC();

BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
GetEmitter()->emitIns_J(INS_jal, block->GetTarget());

// Now go to where the finally funclet needs to return to.
BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
if (nextBlock->NextIs(finallyContinuation) && !compiler->fgInDifferentRegions(nextBlock, finallyContinuation))
{
// Fall-through.
Expand Down
8 changes: 5 additions & 3 deletions src/coreclr/jit/codegenxarch.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -232,10 +232,11 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
{
GetEmitter()->emitIns_R_S(ins_Load(TYP_I_IMPL), EA_PTRSIZE, REG_ARG_0, compiler->lvaPSPSym, 0);
}
GetEmitter()->emitIns_J(INS_call, block->GetTarget());

if (block->HasFlag(BBF_RETLESS_CALL))
{
GetEmitter()->emitIns_J(INS_call, block->GetTarget());

// We have a retless call, and the last instruction generated was a call.
// If the next block is in a different EH region (or is the end of the code
// block), then we need to generate a breakpoint here (since it will never
Expand All @@ -253,13 +254,14 @@ BasicBlock* CodeGen::genCallFinally(BasicBlock* block)
#ifndef JIT32_GCENCODER
// Because of the way the flowgraph is connected, the liveness info for this one instruction
// after the call is not (can not be) correct in cases where a variable has a last use in the
// handler. So turn off GC reporting for this single instruction.
// handler. So turn off GC reporting once we execute the call and reenable after the jmp/nop
GetEmitter()->emitDisableGC();
#endif // JIT32_GCENCODER

BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
GetEmitter()->emitIns_J(INS_call, block->GetTarget());

// Now go to where the finally funclet needs to return to.
BasicBlock* const finallyContinuation = nextBlock->GetFinallyContinuation();
if (nextBlock->NextIs(finallyContinuation) &&
!compiler->fgInDifferentRegions(nextBlock, finallyContinuation))
{
Expand Down
34 changes: 32 additions & 2 deletions src/coreclr/jit/emit.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10482,7 +10482,27 @@ regMaskTP emitter::emitGetGCRegsKilledByNoGCCall(CorInfoHelpFunc helper)
}

#if !defined(JIT32_GCENCODER)
// Start a new instruction group that is not interruptible
//------------------------------------------------------------------------
// emitDisableGC: Requests that the following instruction groups are not GC-interruptible.
//
// Assumptions:
// A NoGC request can be closed by a coresponding emitEnableGC.
// Overlapping/nested NoGC requests are supported - when number of requests
// drops to zero the region is closed. This is not expected to be common.
// A completion of an epilog will close NoGC region in progress and clear the request count
// regardless of request nesting. If a block after the epilog needs to be no-GC, it needs
// to call emitDisableGC() again.
//
// Notes:
// The semantic of NoGC region is that once the first instruction executes,
// some tracking invariants are violated and GC cannot happen, until the execution
// of the last instruction in the region makes GC safe again.
// In particular - once the IP is on the first instruction, but not executed it yet,
// it is still safe to do GC.
// The only special case is when NoGC region is used for prologs/epilogs.
// In such case the GC info could be incorrect until the prolog completes and epilogs
// may have unwindability restrictions, so the first instruction cannot have GC.

void emitter::emitDisableGC()
{
assert(emitNoGCRequestCount < 10); // We really shouldn't have many nested "no gc" requests.
Expand Down Expand Up @@ -10511,7 +10531,17 @@ void emitter::emitDisableGC()
}
}

// Start a new instruction group that is interruptible
//------------------------------------------------------------------------
// emitEnableGC(): Removes a request that the following instruction groups are not GC-interruptible.
//
// Assumptions:
// We should have nonzero count of NoGC requests.
// "emitEnableGC()" reduces the number of requests by 1.
// If the number of requests goes to 0, the subsequent instruction groups are GC-interruptible.
//
// Notes:
// See emitDisableGC for more details.

void emitter::emitEnableGC()
{
assert(emitNoGCRequestCount > 0);
Expand Down
8 changes: 6 additions & 2 deletions src/coreclr/jit/emitinl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -589,9 +589,13 @@ bool emitter::emitGenNoGCLst(Callback& cb)
{
for (insGroup* ig = emitIGlist; ig; ig = ig->igNext)
{
if (ig->igFlags & IGF_NOGCINTERRUPT)
if ((ig->igFlags & IGF_NOGCINTERRUPT) && ig->igSize > 0)
{
if (!cb(ig->igFuncIdx, ig->igOffs, ig->igSize))
emitter::instrDesc* id = emitFirstInstrDesc(ig->igData);
assert(id != nullptr);
assert(id->idCodeSize() > 0);
if (!cb(ig->igFuncIdx, ig->igOffs, ig->igSize, id->idCodeSize(),
ig->igFlags & (IGF_FUNCLET_PROLOG | IGF_FUNCLET_EPILOG | IGF_EPILOG)))
{
return false;
}
Expand Down
55 changes: 33 additions & 22 deletions src/coreclr/jit/gcencode.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4011,41 +4011,53 @@ void GCInfo::gcInfoBlockHdrSave(GcInfoEncoder* gcInfoEncoder, unsigned methodSiz
//
// Encoder should be either GcInfoEncoder or GcInfoEncoderWithLogging
//
struct InterruptibleRangeReporter
class InterruptibleRangeReporter
{
unsigned prevStart;
Encoder* gcInfoEncoderWithLog;
unsigned m_uninterruptibleEnd;
Encoder* m_gcInfoEncoder;
Comment on lines +4016 to +4017
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Make them private as well?


InterruptibleRangeReporter(unsigned _prevStart, Encoder* _gcInfo)
: prevStart(_prevStart)
, gcInfoEncoderWithLog(_gcInfo)
public:
InterruptibleRangeReporter(unsigned prologSize, Encoder* gcInfo)
: m_uninterruptibleEnd(prologSize)
, m_gcInfoEncoder(gcInfo)
{
}

// This callback is called for each insGroup marked with
// IGF_NOGCINTERRUPT (currently just prologs and epilogs).
// This callback is called for each insGroup marked with IGF_NOGCINTERRUPT.
// Report everything between the previous region and the current
// region as interruptible.

bool operator()(unsigned igFuncIdx, unsigned igOffs, unsigned igSize)
bool operator()(
unsigned igFuncIdx, unsigned igOffs, unsigned igSize, unsigned firstInstrSize, bool isInPrologOrEpilog)
{
if (igOffs < prevStart)
if (igOffs < m_uninterruptibleEnd)
{
// We're still in the main method prolog, which has already
// had it's interruptible range reported.
// We're still in the main method prolog, which we know is not interruptible.
assert(igFuncIdx == 0);
assert(igOffs + igSize <= prevStart);
assert(igOffs + igSize <= m_uninterruptibleEnd);
return true;
}

assert(igOffs >= prevStart);
if (igOffs > prevStart)
assert(igOffs >= m_uninterruptibleEnd);
if (igOffs > m_uninterruptibleEnd)
{
gcInfoEncoderWithLog->DefineInterruptibleRange(prevStart, igOffs - prevStart);
// Once the first instruction in IG executes, we cannot have GC.
// But it is ok to have GC while the IP is on the first instruction, unless we are in prolog/epilog.
unsigned interruptibleEnd = igOffs;
if (!isInPrologOrEpilog)
{
interruptibleEnd += firstInstrSize;
}
Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is the key change in this PR.

m_gcInfoEncoder->DefineInterruptibleRange(m_uninterruptibleEnd, interruptibleEnd - m_uninterruptibleEnd);
}
prevStart = igOffs + igSize;
m_uninterruptibleEnd = igOffs + igSize;
return true;
}

unsigned UninterruptibleEnd()
{
return m_uninterruptibleEnd;
}
};

void GCInfo::gcMakeRegPtrTable(
Expand Down Expand Up @@ -4396,17 +4408,16 @@ void GCInfo::gcMakeRegPtrTable(
{
assert(prologSize <= codeSize);

// Now exempt any other region marked as IGF_NOGCINTERRUPT
// Currently just prologs and epilogs.
// Now exempt any region marked as IGF_NOGCINTERRUPT

InterruptibleRangeReporter reporter(prologSize, gcInfoEncoderWithLog);
compiler->GetEmitter()->emitGenNoGCLst(reporter);
prologSize = reporter.prevStart;
unsigned uninterruptibleEnd = reporter.UninterruptibleEnd();

// Report any remainder
if (prologSize < codeSize)
if (uninterruptibleEnd < codeSize)
{
gcInfoEncoderWithLog->DefineInterruptibleRange(prologSize, codeSize - prologSize);
gcInfoEncoderWithLog->DefineInterruptibleRange(uninterruptibleEnd, codeSize - uninterruptibleEnd);
}
}
}
Expand Down
Loading