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[C++11] Add range based accessors for the Use-Def chain of a Value.

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This requires a number of steps.
1) Move value_use_iterator into the Value class as an implementation
   detail
2) Change it to actually be a *Use* iterator rather than a *User*
   iterator.
3) Add an adaptor which is a User iterator that always looks through the
   Use to the User.
4) Wrap these in Value::use_iterator and Value::user_iterator typedefs.
5) Add the range adaptors as Value::uses() and Value::users().
6) Update *all* of the callers to correctly distinguish between whether
   they wanted a use_iterator (and to explicitly dig out the User when
   needed), or a user_iterator which makes the Use itself totally
   opaque.

Because #6 requires churning essentially everything that walked the
Use-Def chains, I went ahead and added all of the range adaptors and
switched them to range-based loops where appropriate. Also because the
renaming requires at least churning every line of code, it didn't make
any sense to split these up into multiple commits -- all of which would
touch all of the same lies of code.

The result is still not quite optimal. The Value::use_iterator is a nice
regular iterator, but Value::user_iterator is an iterator over User*s
rather than over the User objects themselves. As a consequence, it fits
a bit awkwardly into the range-based world and it has the weird
extra-dereferencing 'operator->' that so many of our iterators have.
I think this could be fixed by providing something which transforms
a range of T&s into a range of T*s, but that *can* be separated into
another patch, and it isn't yet 100% clear whether this is the right
move.

However, this change gets us most of the benefit and cleans up
a substantial amount of code around Use and User. =]

llvm-svn: 203364
This commit is contained in:
Chandler Carruth
2014-03-09 03:16:01 +00:00
parent c980afc578
commit cdf4788401
100 changed files with 920 additions and 1075 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
View File

@@ -255,9 +255,7 @@ static bool isSafeAndProfitableToSinkLoad(LoadInst *L) {
// profitable to do this xform.
if (AllocaInst *AI = dyn_cast<AllocaInst>(L->getOperand(0))) {
bool isAddressTaken = false;
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ++UI) {
User *U = *UI;
for (User *U : AI->users()) {
if (isa<LoadInst>(U)) continue;
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
// If storing TO the alloca, then the address isn't taken.
@@ -518,7 +516,7 @@ static bool DeadPHICycle(PHINode *PN,
if (PotentiallyDeadPHIs.size() == 16)
return false;
if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
if (PHINode *PU = dyn_cast<PHINode>(PN->user_back()))
return DeadPHICycle(PU, PotentiallyDeadPHIs);
return false;
@@ -649,32 +647,30 @@ Instruction *InstCombiner::SliceUpIllegalIntegerPHI(PHINode &FirstPhi) {
return 0;
}
for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
for (User *U : PN->users()) {
Instruction *UserI = cast<Instruction>(U);
// If the user is a PHI, inspect its uses recursively.
if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
if (PHINode *UserPN = dyn_cast<PHINode>(UserI)) {
if (PHIsInspected.insert(UserPN))
PHIsToSlice.push_back(UserPN);
continue;
}
// Truncates are always ok.
if (isa<TruncInst>(User)) {
PHIUsers.push_back(PHIUsageRecord(PHIId, 0, User));
if (isa<TruncInst>(UserI)) {
PHIUsers.push_back(PHIUsageRecord(PHIId, 0, UserI));
continue;
}
// Otherwise it must be a lshr which can only be used by one trunc.
if (User->getOpcode() != Instruction::LShr ||
!User->hasOneUse() || !isa<TruncInst>(User->use_back()) ||
!isa<ConstantInt>(User->getOperand(1)))
if (UserI->getOpcode() != Instruction::LShr ||
!UserI->hasOneUse() || !isa<TruncInst>(UserI->user_back()) ||
!isa<ConstantInt>(UserI->getOperand(1)))
return 0;
unsigned Shift = cast<ConstantInt>(User->getOperand(1))->getZExtValue();
PHIUsers.push_back(PHIUsageRecord(PHIId, Shift, User->use_back()));
unsigned Shift = cast<ConstantInt>(UserI->getOperand(1))->getZExtValue();
PHIUsers.push_back(PHIUsageRecord(PHIId, Shift, UserI->user_back()));
}
}
@@ -809,7 +805,7 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
// this PHI only has a single use (a PHI), and if that PHI only has one use (a
// PHI)... break the cycle.
if (PN.hasOneUse()) {
Instruction *PHIUser = cast<Instruction>(PN.use_back());
Instruction *PHIUser = cast<Instruction>(PN.user_back());
if (PHINode *PU = dyn_cast<PHINode>(PHIUser)) {
SmallPtrSet<PHINode*, 16> PotentiallyDeadPHIs;
PotentiallyDeadPHIs.insert(&PN);
@@ -825,7 +821,7 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
// late.
if (PHIUser->hasOneUse() &&
(isa<BinaryOperator>(PHIUser) || isa<GetElementPtrInst>(PHIUser)) &&
PHIUser->use_back() == &PN) {
PHIUser->user_back() == &PN) {
return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
}
}