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Rely on the stdlib's runtime assert and undefined behavior to promote 3/4 remaining unchecked_addr_cast types to object bit casts.

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This commit enables support in the optimizer for promoting the following
unchecked_addr_cast kinds to object bit casts:

1. (Trivial => Trivial) yields a trivial bit cast.
2. (Non-Trivial => Trivial) yields a trivial bit cast.
3. (Non-Trivial => Non-Trivial) yields a ref bit cast.

We do not promote conversions in between trivial and non-trivial types
since a trivial bit cast must have a trivial output and if we allowed
for ref bit casts in between the two, we would be breaking the rule that
ref bit casts do not change the reference semantics of its input, output
types. Technically, we could lower trivial => trivial as a ref cast and
then simplify later but that is unnecessary currently.

<rdar://problem/17373087>

Swift SVN r19784
This commit is contained in:
Michael Gottesman
2014-07-10 05:24:00 +00:00
parent 1563822a8f
commit 0a15d018cc
6 changed files with 37 additions and 239 deletions
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12
lib/SILPasses/LoadStoreOpts.cpp
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@@ -262,11 +262,6 @@ tryToForwardAddressValueToUncheckedAddrToLoad(SILValue Address,
SILType InputTy = UADCI->getOperand().getType();
SILType OutputTy = UADCI->getType();
// If OutputTy is not layout compatible with InputTy, there is nothing we can
// do here.
if(!OutputTy.isLayoutCompatibleWith(InputTy, Mod))
return SILValue();
bool InputIsTrivial = InputTy.isTrivial(Mod);
bool OutputIsTrivial = OutputTy.isTrivial(Mod);
@@ -274,11 +269,16 @@ tryToForwardAddressValueToUncheckedAddrToLoad(SILValue Address,
if (InputTy.hasArchetype() || OutputTy.hasArchetype())
return SILValue();
// If we have a trivial input and a non-trivial output bail.
if (InputIsTrivial && !OutputIsTrivial) {
return SILValue();
}
SILBuilder B(LI);
SILValue CastValue;
// If the output is trivial, we have a trivial bit cast.
if (InputIsTrivial || OutputIsTrivial) {
if (OutputIsTrivial) {
CastValue = B.createUncheckedTrivialBitCast(UADCI->getLoc(), StoredValue,
OutputTy.getObjectType());
} else {