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

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merged 7 commits into from
Jun 24, 2024
Merged

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

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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
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10 changes: 5 additions & 5 deletions src/coreclr/jit/codegenarm.cpp
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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());
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@VSadov VSadov Jun 19, 2024 •
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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,...

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@VSadov VSadov Jun 19, 2024 •
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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
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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
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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
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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
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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
8 changes: 6 additions & 2 deletions src/coreclr/jit/emitinl.h
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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
47 changes: 26 additions & 21 deletions src/coreclr/jit/gcencode.cpp
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Expand Up @@ -4013,37 +4013,43 @@ void GCInfo::gcInfoBlockHdrSave(GcInfoEncoder* gcInfoEncoder, unsigned methodSiz
//
struct InterruptibleRangeReporter
{
unsigned prevStart;
Encoder* gcInfoEncoderWithLog;
unsigned m_uninterruptibleEnd;
Encoder* m_gcInfoEncoder;
Comment on lines +4016 to +4017
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Make them private as well?


InterruptibleRangeReporter(unsigned _prevStart, Encoder* _gcInfo)
: prevStart(_prevStart)
, gcInfoEncoderWithLog(_gcInfo)
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;
}
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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;
}
};
Expand Down Expand Up @@ -4396,17 +4402,16 @@ 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.m_uninterruptibleEnd;

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