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[SILOptimizer] add support for always false comparisons to ArrayBoundsCheckOpts #5622

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Merged
merged 1 commit into from
Nov 3, 2016
Merged

[SILOptimizer] add support for always false comparisons to ArrayBoundsCheckOpts #5622

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41 changes: 41 additions & 0 deletions lib/SILOptimizer/LoopTransforms/ArrayBoundsCheckOpts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1097,6 +1097,38 @@ static bool isComparisonKnownTrue(BuiltinInst *Builtin, InductionInfo &IndVar) {
m_Specific(IndVar.End)));
}

/// Based on the induction variable information this comparison is known to be
/// false.
static bool isComparisonKnownFalse(BuiltinInst *Builtin,
InductionInfo &IndVar) {
if (!IndVar.IsOverflowCheckInserted ||
IndVar.Cmp != BuiltinValueKind::ICMP_EQ)
return false;

// Pattern match a false condition patterns that we can detect and optimize:
// Iteration count < 0 (start)
// Iteration count + 1 <= 0 (start)
// Iteration count + 1 < 0 (start)
// Iteration count + 1 == 0 (start)
auto MatchIndVarHeader = m_Specific(IndVar.HeaderVal);
auto MatchIncrementIndVar = m_TupleExtractInst(
m_ApplyInst(BuiltinValueKind::SAddOver, MatchIndVarHeader, m_One()), 0);
auto MatchIndVarStart = m_Specific(IndVar.Start);

if (match(Builtin,
m_ApplyInst(BuiltinValueKind::ICMP_SLT,
m_CombineOr(MatchIndVarHeader, MatchIncrementIndVar),
MatchIndVarStart)) ||
match(Builtin, m_ApplyInst(BuiltinValueKind::ICMP_EQ,
MatchIncrementIndVar, MatchIndVarStart)) ||
match(Builtin, m_ApplyInst(BuiltinValueKind::ICMP_SLE,
MatchIncrementIndVar, MatchIndVarStart))) {
return true;
}

return false;
}

/// Analyse the loop for arrays that are not modified and perform dominator tree
/// based redundant bounds check removal.
static bool hoistBoundsChecks(SILLoop *Loop, DominanceInfo *DT, SILLoopInfo *LI,
Expand Down Expand Up @@ -1200,6 +1232,15 @@ static bool hoistBoundsChecks(SILLoop *Loop, DominanceInfo *DT, SILLoopInfo *LI,
Changed = true;
continue;
}
if (isComparisonKnownFalse(Builtin, *IV)) {
if (!FalseVal) {
FalseVal = SILValue(B.createIntegerLiteral(
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Are you sure you need the SILValue(...) here? I think just assigning the instruction should just work.

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Using same style as Arnold's isComparisonKnownTrue - but I think yes, as you can see you create the instruction just once if you have multiple comparisons / exists

Builtin->getLoc(), Builtin->getType(), 0));
}
Builtin->replaceAllUsesWith(FalseVal);
Changed = true;
continue;
}
// Check whether a dominating check of the condition let's us
// replace
// the condition by false.
Expand Down
61 changes: 61 additions & 0 deletions test/SILOptimizer/abcopts.sil
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Expand Up @@ -441,6 +441,67 @@ bb3:
return %23 : $Int32
}

// HOIST-LABEL: sil @always_false_hoist
// HOIST: bb4
// HOIST: builtin "sadd_with_overflow_Int32"
// HOIST: tuple_extract
// HOIST-NOT: builtin "cmp_slt_Int32"
// HOIST-NOT: builtin "cmp_sle_Int32"
// HOIST-NOT: builtin "cmp_eq_Int32"
// HOIST: cond_fail
// HOIST: cond_fail
// HOIST: cond_fail
// HOIST: cond_fail
// HOIST: builtin "cmp_eq_Int32"
// HOIST: cond_br
// HOIST: }
sil @always_false_hoist : $@convention(thin) (@owned Array<Int>) -> () {
bb0(%0 : $Array<Int>):
%z0 = integer_literal $Builtin.Int32, 0
%f1 = function_ref @getCount2 : $@convention(method) (@owned Array<Int>) -> Int32
retain_value %0 : $Array<Int>
%t1 = apply %f1(%0) : $@convention(method) (@owned Array<Int>) -> Int32
%c1 = struct_extract %t1 : $Int32, #Int32._value
%t2 = builtin "cmp_eq_Int32"(%z0 : $Builtin.Int32, %c1 : $Builtin.Int32) : $Builtin.Int1
cond_br %t2, bb5, bb1

bb1:
br bb2(%z0 : $Builtin.Int32)

bb2(%i0 : $Builtin.Int32):
cond_br undef, bb3, bb4

bb3:
%f2 = function_ref @checkbounds2 : $@convention(method) (Int32, Bool, @owned Array<Int>) -> _DependenceToken
retain_value %0 : $Array<Int>
%t3 = struct $Int32(%i0 : $Builtin.Int32)

br bb4

bb4:
%t5 = integer_literal $Builtin.Int1, 0
%i2 = integer_literal $Builtin.Int32, 1
%t6 = builtin "sadd_with_overflow_Int32"(%i0 : $Builtin.Int32, %i2 : $Builtin.Int32, %t5 : $Builtin.Int1) : $(Builtin.Int32, Builtin.Int1)
%t7 = tuple_extract %t6 : $(Builtin.Int32, Builtin.Int1), 0
%t8 = tuple_extract %t6 : $(Builtin.Int32, Builtin.Int1), 1
cond_fail %t8 : $Builtin.Int1
%af1 = builtin "cmp_slt_Int32"(%i0 : $Builtin.Int32, %z0 : $Builtin.Int32) : $Builtin.Int1
cond_fail %af1 : $Builtin.Int1
%af2 = builtin "cmp_slt_Int32"(%t7 : $Builtin.Int32, %z0 : $Builtin.Int32) : $Builtin.Int1
cond_fail %af2 : $Builtin.Int1
%af3 = builtin "cmp_sle_Int32"(%t7 : $Builtin.Int32, %z0 : $Builtin.Int32) : $Builtin.Int1
cond_fail %af3 : $Builtin.Int1
%af4 = builtin "cmp_eq_Int32"(%t7 : $Builtin.Int32, %z0 : $Builtin.Int32) : $Builtin.Int1
cond_fail %af4 : $Builtin.Int1
%8 = builtin "cmp_eq_Int32"(%t7 : $Builtin.Int32, %c1 : $Builtin.Int32) : $Builtin.Int1
cond_br %8, bb5, bb2(%t7 : $Builtin.Int32)

bb5:
%r1 = tuple ()
return %r1 : $()
}


// HOIST-LABEL: sil @hoistinvariant

// Preheader.
Expand Down