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JIT: fix loop cloning when loop's last block is within a hander #111432

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merged 2 commits into from
Jan 15, 2025
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JIT: fix loop cloning when loop's last block is within a hander #111432

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JIT: fix loop cloning when loop's last block is within a hander
AndyAyersMS Jan 14, 2025
d4d226e
use fgFindInsertPoint
AndyAyersMS Jan 15, 2025
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33 changes: 21 additions & 12 deletions src/coreclr/jit/loopcloning.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2067,8 +2067,19 @@ void Compiler::optCloneLoop(FlowGraphNaturalLoop* loop, LoopCloneContext* contex
// bottomRedirBlk [BBJ_ALWAYS --> bottomNext]
// ... slow cloned loop (not yet inserted)
// bottomNext
BasicBlock* bottom = loop->GetLexicallyBottomMostBlock();
BasicBlock* newPred = bottom;
BasicBlock* bottom = loop->GetLexicallyBottomMostBlock();
BasicBlock* beforeSlowPreheader = bottom;

// Ensure the slow loop preheader ends up in the same EH region
// as the preheader.
//
bool inTry = false;
unsigned const enclosingRegion = ehGetMostNestedRegionIndex(preheader, &inTry);
if (!BasicBlock::sameEHRegion(beforeSlowPreheader, preheader))
{
beforeSlowPreheader = fgFindInsertPoint(enclosingRegion, inTry, bottom, /* endBlk */ nullptr,
/* nearBlk */ bottom, /* jumpBlk */ nullptr, /* runRarely */ false);
}

// Create a new preheader for the slow loop immediately before the slow
// loop itself. All failed conditions will branch to the slow preheader.
Expand All @@ -2078,22 +2089,20 @@ void Compiler::optCloneLoop(FlowGraphNaturalLoop* loop, LoopCloneContext* contex
// The slow preheader needs to go in the same EH region as the preheader.
//
JITDUMP("Create unique preheader for slow path loop\n");
const bool extendRegion = BasicBlock::sameEHRegion(bottom, preheader);
BasicBlock* slowPreheader = fgNewBBafter(BBJ_ALWAYS, newPred, extendRegion);
JITDUMP("Adding " FMT_BB " after " FMT_BB "\n", slowPreheader->bbNum, newPred->bbNum);
slowPreheader->bbWeight = newPred->isRunRarely() ? BB_ZERO_WEIGHT : ambientWeight;
slowPreheader->CopyFlags(newPred, (BBF_PROF_WEIGHT | BBF_RUN_RARELY));
const bool extendRegion = BasicBlock::sameEHRegion(beforeSlowPreheader, preheader);
BasicBlock* slowPreheader = fgNewBBafter(BBJ_ALWAYS, beforeSlowPreheader, extendRegion);
JITDUMP("Adding " FMT_BB " after " FMT_BB "\n", slowPreheader->bbNum, beforeSlowPreheader->bbNum);
slowPreheader->bbWeight = preheader->isRunRarely() ? BB_ZERO_WEIGHT : ambientWeight;
slowPreheader->CopyFlags(preheader, (BBF_PROF_WEIGHT | BBF_RUN_RARELY));
slowPreheader->scaleBBWeight(LoopCloneContext::slowPathWeightScaleFactor);

// If we didn't extend the region above (because the last loop
// If we didn't extend the region above (because the beforeSlowPreheader
// block was in some enclosed EH region), put the slow preheader
// into the appropriate region, and make appropriate extent updates.
//
if (!extendRegion)
{
slowPreheader->copyEHRegion(preheader);
bool isTry = false;
unsigned enclosingRegion = ehGetMostNestedRegionIndex(slowPreheader, &isTry);

if (enclosingRegion != 0)
{
Expand All @@ -2111,11 +2120,11 @@ void Compiler::optCloneLoop(FlowGraphNaturalLoop* loop, LoopCloneContext* contex
}
}
}
newPred = slowPreheader;

// Now we'll clone the blocks of the loop body. These cloned blocks will be the slow path.

//
BlockToBlockMap* blockMap = new (getAllocator(CMK_LoopClone)) BlockToBlockMap(getAllocator(CMK_LoopClone));
BasicBlock* newPred = slowPreheader;

if (cloneLoopsWithEH)
{
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