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[silcombine] Eliminate mark_dependence whose base is a trivial object. #30051

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Merged
merged 1 commit into from
Feb 25, 2020
Merged

[silcombine] Eliminate mark_dependence whose base is a trivial object. #30051

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32 changes: 22 additions & 10 deletions lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1681,36 +1681,48 @@ SILInstruction *SILCombiner::visitEnumInst(EnumInst *EI) {
return nullptr;
}

SILInstruction *SILCombiner::visitMarkDependenceInst(MarkDependenceInst *MDI) {
SILInstruction *SILCombiner::visitMarkDependenceInst(MarkDependenceInst *mdi) {
// Simplify the base operand of a MarkDependenceInst to eliminate unnecessary
// instructions that aren't adding value.
//
// Conversions to Optional.Some(x) often happen here, this isn't important
// for us, we can just depend on 'x' directly.
if (auto eiBase = dyn_cast<EnumInst>(MDI->getBase())) {
if (auto *eiBase = dyn_cast<EnumInst>(mdi->getBase())) {
if (eiBase->hasOperand() && eiBase->hasOneUse()) {
MDI->setBase(eiBase->getOperand());
mdi->setBase(eiBase->getOperand());
eraseInstFromFunction(*eiBase);
return MDI;
return mdi;
}
}

// Conversions from a class to AnyObject also happen a lot, we can just depend
// on the class reference.
if (auto ier = dyn_cast<InitExistentialRefInst>(MDI->getBase())) {
MDI->setBase(ier->getOperand());
if (auto *ier = dyn_cast<InitExistentialRefInst>(mdi->getBase())) {
mdi->setBase(ier->getOperand());
if (ier->use_empty())
eraseInstFromFunction(*ier);
return MDI;
return mdi;
}

// Conversions from a class to AnyObject also happen a lot, we can just depend
// on the class reference.
if (auto oeri = dyn_cast<OpenExistentialRefInst>(MDI->getBase())) {
MDI->setBase(oeri->getOperand());
if (auto *oeri = dyn_cast<OpenExistentialRefInst>(mdi->getBase())) {
mdi->setBase(oeri->getOperand());
if (oeri->use_empty())
eraseInstFromFunction(*oeri);
return MDI;
return mdi;
}

// Sometimes due to specialization/builtins, we can get a mark_dependence
// whose base is a trivial typed object. In such a case, the mark_dependence
// does not have a meaning, so just eliminate it.
{
SILType baseType = mdi->getBase()->getType();
if (baseType.isObject() && baseType.isTrivial(*mdi->getFunction())) {
SILValue value = mdi->getValue();
mdi->replaceAllUsesWith(value);
return eraseInstFromFunction(*mdi);
}
}

return nullptr;
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13 changes: 13 additions & 0 deletions test/SILOptimizer/sil_combine.sil
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Original file line number Diff line number Diff line change
Expand Up @@ -3449,6 +3449,19 @@ bb0(%0 : $*Builtin.Int64, %1 : $B):
return %4 : $Builtin.Int64
}

// CHECK-LABEL: sil @mark_dependence_trivial_object_base :
// CHECK: bb0(
// CHECK-NEXT: strong_retain
// CHECK-NEXT: return
// CHECK: } // end sil function 'mark_dependence_trivial_object_base'
sil @mark_dependence_trivial_object_base : $@convention(thin) (@guaranteed B) -> @owned B {
bb0(%0 : $B):
strong_retain %0 : $B
%1 = enum $Optional<Int>, #Optional.none!enumelt
%2 = mark_dependence %0 : $B on %1 : $Optional<Int>
return %2 : $B
}

protocol _NSArrayCore {}

// CHECK-LABEL: sil @mark_dependence_base2
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