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Move "switch recognition" phase to be before "optimize bools" #113866

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Move "switch recognition" phase to be before "optimize bools" #113866

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7a44d86
Invoke "switch recognition" phase before "optimize bools"
EgorBo Mar 25, 2025
82580e9
Fix infinite loop by adding continue statement
EgorBo Mar 25, 2025
d56cce3
Comment out BBJ_COND block optimization code
EgorBo Mar 25, 2025
b07fef5
improve diffs
EgorBo Mar 25, 2025
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8 changes: 4 additions & 4 deletions src/coreclr/jit/compiler.cpp
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Expand Up @@ -4946,6 +4946,10 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl

if (opts.OptimizationEnabled())
{
// Conditional to switch conversion, and switch peeling
//
DoPhase(this, PHASE_SWITCH_RECOGNITION, &Compiler::optRecognizeAndOptimizeSwitchJumps);

// Optimize boolean conditions
//
DoPhase(this, PHASE_OPTIMIZE_BOOLS, &Compiler::optOptimizeBools);
Expand All @@ -4954,10 +4958,6 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
//
DoPhase(this, PHASE_IF_CONVERSION, &Compiler::optIfConversion);

// Conditional to switch conversion, and switch peeling
//
DoPhase(this, PHASE_SWITCH_RECOGNITION, &Compiler::optRecognizeAndOptimizeSwitchJumps);

// Run flow optimizations before reordering blocks
//
DoPhase(this, PHASE_OPTIMIZE_PRE_LAYOUT, &Compiler::optOptimizePreLayout);
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2 changes: 1 addition & 1 deletion src/coreclr/jit/optimizebools.cpp
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Expand Up @@ -1715,7 +1715,7 @@ bool Compiler::fgFoldCondToReturnBlock(BasicBlock* block)
modified = true;
}
// Same here - bail out if the block is no longer BBJ_COND after compacting.
if (!block->KindIs(BBJ_COND))
if (block->HasFlag(BBF_REMOVED) || !block->KindIs(BBJ_COND))
{
return modified;
}
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23 changes: 23 additions & 0 deletions src/coreclr/jit/switchrecognition.cpp
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Expand Up @@ -32,6 +32,29 @@ PhaseStatus Compiler::optRecognizeAndOptimizeSwitchJumps()
continue;
}

// Before we start, let's optimize possible fallthrough blocks for BBJ_COND's successors.
if (block->KindIs(BBJ_COND) && block->hasSingleStmt())
{
BasicBlock* retFalseBb = block->GetFalseTarget();
BasicBlock* retTrueBb = block->GetTrueTarget();
if (fgCanCompactBlock(retTrueBb) && retTrueBb->isEmpty())
{
fgCompactBlock(retTrueBb);
modified = true;
}
// fgCompactBlock could have removed retFalseBb and the block, so we
// need to check BBF_REMOVED flag for both.
if (!retFalseBb->HasFlag(BBF_REMOVED) && fgCanCompactBlock(retFalseBb))
{
fgCompactBlock(retFalseBb);
modified = true;
}
if (block->HasFlag(BBF_REMOVED))
{
continue;
}
}

// Limit to XARCH, ARM is already doing a great job with such comparisons using
// a series of ccmp instruction (see ifConvert phase).
#ifdef TARGET_XARCH
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