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SIL: fix a bug which can cause the stack nesting to get broken by loop unrolling #5395

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Merged
merged 1 commit into from
Oct 21, 2016
Merged

SIL: fix a bug which can cause the stack nesting to get broken by loop unrolling #5395

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14 changes: 8 additions & 6 deletions lib/SIL/LoopInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,12 +36,12 @@ SILLoopInfo::SILLoopInfo(SILFunction *F, DominanceInfo *DT) {
}

bool SILLoop::canDuplicate(SILInstruction *I) const {
// The dealloc_stack of an alloc_stack must be in the loop, otherwise the
// dealloc_stack will be fed by a phi node of two alloc_stacks.
if (auto *Alloc = dyn_cast<AllocStackInst>(I)) {
for (auto *UI : Alloc->getUses()) {
if (auto *Dealloc = dyn_cast<DeallocStackInst>(UI->getUser())) {
if (!contains(Dealloc->getParent()))
// The deallocation of a stack allocation must be in the loop, otherwise the
// deallocation will be fed by a phi node of two allocations.
if (I->isAllocatingStack()) {
for (auto *UI : I->getUses()) {
if (UI->getUser()->isDeallocatingStack()) {
if (!contains(UI->getUser()->getParent()))
return false;
}
}
Expand Down Expand Up @@ -76,6 +76,8 @@ bool SILLoop::canDuplicate(SILInstruction *I) const {
return false;
}

assert(I->isTriviallyDuplicatable() &&
"Code here must match isTriviallyDuplicatable in SILInstruction");
return true;
}

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68 changes: 68 additions & 0 deletions test/SILOptimizer/loop_unroll.sil
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Expand Up @@ -70,3 +70,71 @@ bb3:
%8 = tuple()
return %8 : $()
}

class B {}

// CHECK-LABEL: sil @unroll_with_stack_allocation
// CHECK: = alloc_ref [stack]
// CHECK: dealloc_ref [stack]
// CHECK: = alloc_ref [stack]
// CHECK: dealloc_ref [stack]
// CHECK: }
sil @unroll_with_stack_allocation : $@convention(thin) () -> () {
bb0:
%0 = integer_literal $Builtin.Int64, 0
%1 = integer_literal $Builtin.Int64, 1
%2 = integer_literal $Builtin.Int64, 2
%3 = integer_literal $Builtin.Int1, 1
br bb1(%0 : $Builtin.Int64)

bb1(%4 : $Builtin.Int64):
%a = alloc_ref [stack] $B
br bb2

bb2:
%5 = builtin "sadd_with_overflow_Int64"(%4 : $Builtin.Int64, %1 : $Builtin.Int64, %3 : $Builtin.Int1) : $(Builtin.Int64, Builtin.Int1)
%6 = tuple_extract %5 : $(Builtin.Int64, Builtin.Int1), 0
%7 = builtin "cmp_eq_Int64"(%6 : $Builtin.Int64, %2 : $Builtin.Int64) : $Builtin.Int1
dealloc_ref [stack] %a : $B
cond_br %7, bb4, bb3

bb3:
br bb1(%6 : $Builtin.Int64)

bb4:
%8 = tuple()
return %8 : $()
}

// CHECK-LABEL: sil @dont_copy_stack_allocation_with_dealloc_outside_loop
// CHECK: = alloc_ref [stack]
// CHECK: bb2:
// CHECK: dealloc_ref [stack]
// CHECK: bb3:
// CHECK: dealloc_ref [stack]
// CHECK-NEXT: tuple
// CHECK-NEXT: return
sil @dont_copy_stack_allocation_with_dealloc_outside_loop : $@convention(thin) () -> () {
bb0:
%0 = integer_literal $Builtin.Int64, 0
%1 = integer_literal $Builtin.Int64, 1
%2 = integer_literal $Builtin.Int64, 2
%3 = integer_literal $Builtin.Int1, 1
br bb1(%0 : $Builtin.Int64)

bb1(%4 : $Builtin.Int64):
%a = alloc_ref [stack] $B
%5 = builtin "sadd_with_overflow_Int64"(%4 : $Builtin.Int64, %1 : $Builtin.Int64, %3 : $Builtin.Int1) : $(Builtin.Int64, Builtin.Int1)
%6 = tuple_extract %5 : $(Builtin.Int64, Builtin.Int1), 0
%7 = builtin "cmp_eq_Int64"(%6 : $Builtin.Int64, %2 : $Builtin.Int64) : $Builtin.Int1
cond_br %7, bb3, bb2

bb2:
dealloc_ref [stack] %a : $B
br bb1(%6 : $Builtin.Int64)

bb3:
dealloc_ref [stack] %a : $B
%8 = tuple()
return %8 : $()
}