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Remove debug instructions on dead temporaries in CopyForwarding (#32941)

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This commit is contained in:
Meghana Gupta
2020-07-21 18:14:58 -07:00
committed by GitHub
parent a2c5f05e97
commit 858fe6c593
2 changed files with 36 additions and 11 deletions
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45
lib/SILOptimizer/Transforms/CopyForwarding.cpp
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@@ -612,8 +612,10 @@ public:
protected:
bool propagateCopy(CopyAddrInst *CopyInst, bool hoistingDestroy);
CopyAddrInst *findCopyIntoDeadTemp(CopyAddrInst *destCopy);
bool forwardDeadTempCopy(CopyAddrInst *srcCopy, CopyAddrInst *destCopy);
CopyAddrInst *findCopyIntoDeadTemp(
CopyAddrInst *destCopy,
SmallVectorImpl<DebugValueAddrInst *> &debugInstsToDelete);
bool forwardDeadTempCopy(CopyAddrInst *destCopy);
bool forwardPropagateCopy();
bool backwardPropagateCopy();
bool hoistDestroy(SILInstruction *DestroyPoint, SILLocation DestroyLoc);
@@ -681,12 +683,10 @@ propagateCopy(CopyAddrInst *CopyInst, bool hoistingDestroy) {
// Handle copy-of-copy without analyzing uses.
// Assumes that CurrentCopy->getSrc() is dead after CurrentCopy.
assert(CurrentCopy->isTakeOfSrc() || hoistingDestroy);
if (auto *srcCopy = findCopyIntoDeadTemp(CurrentCopy)) {
if (forwardDeadTempCopy(srcCopy, CurrentCopy)) {
HasChanged = true;
++NumDeadTemp;
return true;
}
if (forwardDeadTempCopy(CurrentCopy)) {
HasChanged = true;
++NumDeadTemp;
return true;
}
if (forwardPropagateCopy()) {
@@ -737,7 +737,9 @@ propagateCopy(CopyAddrInst *CopyInst, bool hoistingDestroy) {
/// Unlike the forward and backward propagation that finds all use points, this
/// handles copies of address projections. By conservatively checking all
/// intervening instructions, it avoids the need to analyze projection paths.
CopyAddrInst *CopyForwarding::findCopyIntoDeadTemp(CopyAddrInst *destCopy) {
CopyAddrInst *CopyForwarding::findCopyIntoDeadTemp(
CopyAddrInst *destCopy,
SmallVectorImpl<DebugValueAddrInst *> &debugInstsToDelete) {
auto tmpVal = destCopy->getSrc();
assert(tmpVal == CurrentDef);
assert(isIdentifiedSourceValue(tmpVal));
@@ -750,8 +752,20 @@ CopyAddrInst *CopyForwarding::findCopyIntoDeadTemp(CopyAddrInst *destCopy) {
if (srcCopy->getDest() == tmpVal)
return srcCopy;
}
// 'SrcUserInsts' consists of all users of the 'temp'
if (SrcUserInsts.count(UserInst))
return nullptr;
// Collect all debug_value_addr instructions between temp to dest copy and
// src to temp copy. On success, these debug_value_addr instructions should
// be deleted.
if (auto *debugUser = dyn_cast<DebugValueAddrInst>(UserInst)) {
// 'SrcDebugValueInsts' consists of all the debug users of 'temp'
if (SrcDebugValueInsts.count(debugUser))
debugInstsToDelete.push_back(debugUser);
continue;
}
if (UserInst->mayWriteToMemory())
return nullptr;
}
@@ -780,12 +794,16 @@ CopyAddrInst *CopyForwarding::findCopyIntoDeadTemp(CopyAddrInst *destCopy) {
/// - %temp is uninitialized following `srcCopy` and subsequent instruction
/// attempts to destroy this uninitialized value.
bool CopyForwarding::
forwardDeadTempCopy(CopyAddrInst *srcCopy, CopyAddrInst *destCopy) {
forwardDeadTempCopy(CopyAddrInst *destCopy) {
SmallVector<DebugValueAddrInst*, 2> debugInstsToDelete;
auto *srcCopy = findCopyIntoDeadTemp(CurrentCopy, debugInstsToDelete);
if (!srcCopy)
return false;
LLVM_DEBUG(llvm::dbgs() << " Temp Copy:" << *srcCopy
<< " to " << *destCopy);
assert(srcCopy->getDest() == destCopy->getSrc());
// This pattern can be trivially folded without affecting %temp destroys:
// copy_addr [...] %src, [init] %temp
// copy_addr [take] %temp, [...] %dest
@@ -798,6 +816,11 @@ forwardDeadTempCopy(CopyAddrInst *srcCopy, CopyAddrInst *destCopy) {
.createDestroyAddr(srcCopy->getLoc(), srcCopy->getDest());
}
// Delete all dead debug_value_addr instructions
for (auto *deadDebugUser : debugInstsToDelete) {
deadDebugUser->eraseFromParent();
}
// Either `destCopy` is a take, or the caller is hoisting a destroy:
// copy_addr %temp, %dest
// ...