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Simplify JIT label handling #51208

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Apr 15, 2021
Merged

Simplify JIT label handling #51208

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80aa2bf
Simplify JIT label handling
BruceForstall Apr 13, 2021
7c1f38d
Remove loop align flag if we decide a loop is no longer a loop
BruceForstall Apr 15, 2021
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2 changes: 1 addition & 1 deletion src/coreclr/jit/emit.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4667,7 +4667,7 @@ void emitter::emitLoopAlignment()
//-----------------------------------------------------------------------------
// emitEndsWithAlignInstr: Checks if current IG ends with loop align instruction.
//
// Returns: true if current IG ends with align instruciton.
// Returns: true if current IG ends with align instruction.
//
bool emitter::emitEndsWithAlignInstr()
{
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11 changes: 11 additions & 0 deletions src/coreclr/jit/optimizer.cpp
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Expand Up @@ -366,6 +366,17 @@ void Compiler::optUnmarkLoopBlocks(BasicBlock* begBlk, BasicBlock* endBlk)
break;
}
}

JITDUMP("\n");

#if FEATURE_LOOP_ALIGN
if (begBlk->isLoopAlign())
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Ah, good catch, I think I missed this earlier although there was one rare case that I handled in :

runtime/src/coreclr/jit/morph.cpp

Lines 16607 to 16610 in f958f2b

#if FEATURE_LOOP_ALIGN
optLoopTable[loopNum].lpFirst->bbFlags &= ~BBF_LOOP_ALIGN;
JITDUMP("Removing LOOP_ALIGN flag from bogus loop in " FMT_BB "\n",
optLoopTable[loopNum].lpFirst->bbNum);

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I just sent out draft PR #51313 to test how often we retain align flag on blocks that are no longer loop. Probably not because we might have hit an assert during codegen, but just want to double check.

{
// Clear the loop alignment bit on the head of a loop, since it's no longer a loop.
begBlk->bbFlags &= ~BBF_LOOP_ALIGN;
JITDUMP("Removing LOOP_ALIGN flag from removed loop in " FMT_BB "\n", begBlk->bbNum);
}
#endif
}

/*****************************************************************************************************
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