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Disable TempRValueOpt when there are users of the temp object preceding the copy #66328

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Merged
merged 1 commit into from
Jun 5, 2023
Merged

Disable TempRValueOpt when there are users of the temp object preceding the copy #66328

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18 changes: 18 additions & 0 deletions lib/SILOptimizer/Transforms/TempRValueElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -547,9 +547,13 @@ void TempRValueOptPass::tryOptimizeCopyIntoTemp(CopyAddrInst *copyInst) {
// only users that modify memory are the copy_addr [initialization] and
// destroy_addr.
InstructionSetWithSize loadInsts(getFunction());
// Set of tempObj users
InstructionSet userSet(getFunction());
for (auto *useOper : tempObj->getUses()) {
SILInstruction *user = useOper->getUser();

userSet.insert(user);

if (user == copyInst)
continue;

Expand All @@ -576,6 +580,20 @@ void TempRValueOptPass::tryOptimizeCopyIntoTemp(CopyAddrInst *copyInst) {
return;
}

// Check and return without optimization if we have any users of tempObj that
// precede the copyInst.
// This can happen with projections.
// TODO: We can enable this case if we clone the projections at "load" uses

// All instructions in userSet are in the same block as copyInst. collectLoads
// ensures of this.
for (SILInstruction &inst : llvm::make_range(copyInst->getParent()->begin(),
copyInst->getIterator())) {
if (userSet.contains(&inst)) {
return;
}
}

AliasAnalysis *aa = getPassManager()->getAnalysis<AliasAnalysis>(getFunction());

// Check if the source is modified within the lifetime of the temporary.
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18 changes: 18 additions & 0 deletions test/SILOptimizer/temp_rvalue_opt_ossa.sil
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Expand Up @@ -1847,3 +1847,21 @@ bb0:
dealloc_stack %src : $*MOS
return %instance_3 : $MOS
}

// CHECK-LABEL: sil [ossa] @dont_optimize_use_before_copy :
// CHECK: copy_addr
// CHECK-LABEL: } // end sil function 'dont_optimize_use_before_copy'
sil [ossa] @dont_optimize_use_before_copy : $@convention(thin) <B> (@in_guaranteed GS<B>, @inout GS<B>) -> () {
bb0(%0 : $*GS<B>, %1 : $*GS<B>):
%2 = alloc_stack $GS<B>
%3 = struct_element_addr %2 : $*GS<B>, #GS._value
copy_addr %1 to [init] %2 : $*GS<B>
%5 = load [trivial] %3 : $*Builtin.Int64
%6 = builtin "cmp_slt_Int64"(%5 : $Builtin.Int64, %5 : $Builtin.Int64) : $Builtin.Int1
copy_addr %2 to %1 : $*GS<B>
destroy_addr %2 : $*GS<B>
dealloc_stack %2 : $*GS<B>
%10 = tuple ()
return %10 : $()
}