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Move the validation of uses of the box pointer into a separate function.

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Eventually we'll scan one level deep into the body of a partial_apply to
validate uses there, and use the same logic.

Swift SVN r15553
This commit is contained in:
Mark Lacey
2014-03-27 05:24:52 +00:00
parent d084edd951
commit 0bb09627ab
1 changed files with 30 additions and 14 deletions
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44
lib/SILPasses/AllocBoxToStack.cpp
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@@ -137,28 +137,44 @@ void getFinalReleases(AllocBoxInst *ABI,
addLastRelease(Box, BB, Releases);
}
/// canPromoteAllocBox - Can we promote this alloc_box to an alloc_stack?
static bool canPromoteAllocBox(AllocBoxInst *ABI) {
// Scan all of the uses of the alloc_box to see if any of them cause
// address of the held value to escape, in which case we can't
// promote it to live on the stack.
if (canValueEscape(ABI->getAddressResult()))
return false;
/// findUnexpectedBoxUse - Validate that the uses of a pointer to a
/// box do not eliminate it from consideration for promotion to a
/// stack element. Return the instruction with the unexpected use if
/// we find one.
static SILInstruction* findUnexpectedBoxUse(SILValue Box) {
assert((Box.getType() ==
SILType::getObjectPointerType(Box.getType().getASTContext())) &&
"Expected an object pointer!");
// Scan all of the uses of the retain count value, collecting all the releases
// and validating that we don't have an unexpected user.
for (auto UI : ABI->getContainerResult().getUses()) {
for (auto UI : Box.getUses()) {
auto *User = UI->getUser();
if (isa<StrongRetainInst>(User))
// Retains, releases, and deallocs are fine.
if (isa<StrongRetainInst>(User) || isa<StrongReleaseInst>(User) ||
isa<DeallocBoxInst>(User))
continue;
// Release doesn't either, but we want to keep track of where this value
// gets released.
if (isa<StrongReleaseInst>(User) || isa<DeallocBoxInst>(User))
continue;
return User;
}
// Otherwise, this looks like it escapes.
return nullptr;
}
/// canPromoteAllocBox - Can we promote this alloc_box to an alloc_stack?
static bool canPromoteAllocBox(AllocBoxInst *ABI) {
// Scan all of the uses of the address of the box's contained value
// to see if any of them cause address to escape, in which case we
// can't promote it to live on the stack.
if (canValueEscape(ABI->getAddressResult()))
return false;
// Scan all of the uses of the address of the box to see if any
// disqualifies the box from being promoted tot he stack.
if (auto *User = findUnexpectedBoxUse(ABI->getContainerResult())) {
// Otherwise, we have an unexpected use.
DEBUG(llvm::dbgs() << "*** Failed to promote alloc_box in @"
<< ABI->getFunction()->getName() << ": " << *ABI
<< " Due to user: " << *User << "\n");