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FunctionSignatureOptimization: fix a miscompile in owned->guaranteed return value specialization #31581

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Merged
merged 1 commit into from
May 8, 2020
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FunctionSignatureOptimization: fix a miscompile in owned->guaranteed return value specialization #31581

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8 changes: 5 additions & 3 deletions include/swift/SILOptimizer/Analysis/EpilogueARCAnalysis.h
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Original file line number Diff line number Diff line change
Expand Up @@ -200,9 +200,11 @@ class EpilogueARCContext {
// We are checking for retain. If this is a self-recursion. call
// to the function (which returns an owned value) can be treated as
// the retain instruction.
if (auto *AI = dyn_cast<ApplyInst>(II))
if (AI->getCalleeFunction() == II->getParent()->getParent())
return true;
if (auto *AI = dyn_cast<ApplyInst>(II)) {
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LGTM. Can you in a follow on commit add a comment here reminding the user that arg is going to be a return value of the function since we are performing retain motion. I was confused at first b/c of getArg.

return AI->getCalleeFunction() == II->getParent()->getParent() &&
RCFI->getRCIdentityRoot(AI) ==
RCFI->getRCIdentityRoot(getArg(AI->getParent()));
}
// Check whether this is a retain instruction and the argument it
// retains.
return isRetainInstruction(II) &&
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2 changes: 1 addition & 1 deletion test/SILOptimizer/epilogue_arc_dumper.sil
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Expand Up @@ -180,7 +180,7 @@ bb3:
}

// CHECK-LABEL: START: epilogue_retains_in_diamond_top_and_left_split_block
// CHECK: apply
// CHECK-NOT: apply
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Can you add in a follow on commit a test to this file of this form that still has the old behavior if we don't currently have a test. I didn't check.

// CHECK: FINISH: epilogue_retains_in_diamond_top_and_left_split_block
sil @epilogue_retains_in_diamond_top_and_left_split_block : $@convention(thin) (@owned foo) -> @owned foo {
bb0(%0 : $foo):
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38 changes: 38 additions & 0 deletions test/SILOptimizer/functionsigopts.sil
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Expand Up @@ -63,6 +63,11 @@ public class KlassBar : KlassFoo {
init()
}

indirect public enum IndirectEnum : Hashable {
case A
case B(IndirectEnum)
}

sil @use_Int : $@convention(thin) (Int) -> ()
sil @use_Int64 : $@convention(thin) (Int64) -> ()
sil @use_Generic : $@convention(thin) <T>(@in_guaranteed T) -> ()
Expand Down Expand Up @@ -514,6 +519,39 @@ bb0(%0 : $boo):
return %0 : $boo
}

// CHECK-LABEL: sil @no_fso_recursive_result_is_not_returned :
// CHECK-NOT: release_value
// CHECK: bb2:
// CHECK-NEXT: retain_value %0
// CHECK: return
// CHECK-LABEL: } // end sil function 'no_fso_recursive_result_is_not_returned'
sil @no_fso_recursive_result_is_not_returned : $@convention(method) (@guaranteed IndirectEnum, @guaranteed IndirectEnum) -> @owned IndirectEnum {
bb0(%0 : $IndirectEnum, %1 : $IndirectEnum):
switch_enum %1 : $IndirectEnum, case #IndirectEnum.B!enumelt: bb1, default bb2

bb1(%3 : ${ var IndirectEnum }):
%4 = project_box %3 : ${ var IndirectEnum }, 0
%5 = load %4 : $*IndirectEnum
%6 = function_ref @no_fso_recursive_result_is_not_returned : $@convention(method) (@guaranteed IndirectEnum, @guaranteed IndirectEnum) -> @owned IndirectEnum

// The result of the self-recursion is not returned (but put in a box).
// This prevents guaranteed -> owned return value specialization.
%7 = apply %6(%0, %5) : $@convention(method) (@guaranteed IndirectEnum, @guaranteed IndirectEnum) -> @owned IndirectEnum
%8 = alloc_box ${ var IndirectEnum }
%9 = project_box %8 : ${ var IndirectEnum }, 0
store %7 to %9 : $*IndirectEnum
%11 = enum $IndirectEnum, #IndirectEnum.B!enumelt, %8 : ${ var IndirectEnum }
br bb3(%11 : $IndirectEnum)

bb2:
retain_value %0 : $IndirectEnum
br bb3(%0 : $IndirectEnum)

bb3(%35 : $IndirectEnum):
return %35 : $IndirectEnum
}


// Make sure we do not move the retain_value in the throw block.
//
// CHECK-LABEL: sil [serialized] [signature_optimized_thunk] [always_inline] @owned_to_unowned_retval_with_error_result : $@convention(thin) (@owned boo) -> (@owned boo, @error Error) {
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