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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. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203364 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth
2014-03-09 03:16:01 +00:00
parent b033b03c23
commit 36b699f2b1
100 changed files with 920 additions and 1075 deletions
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17
lib/Transforms/Utils/LCSSA.cpp
View File

@@ -65,15 +65,14 @@ static bool processInstruction(Loop &L, Instruction &Inst, DominatorTree &DT,
BasicBlock *InstBB = Inst.getParent();
for (Value::use_iterator UI = Inst.use_begin(), E = Inst.use_end(); UI != E;
++UI) {
User *U = *UI;
BasicBlock *UserBB = cast<Instruction>(U)->getParent();
if (PHINode *PN = dyn_cast<PHINode>(U))
UserBB = PN->getIncomingBlock(UI);
for (Use &U : Inst.uses()) {
Instruction *User = cast<Instruction>(U.getUser());
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User))
UserBB = PN->getIncomingBlock(U);
if (InstBB != UserBB && !L.contains(UserBB))
UsesToRewrite.push_back(&UI.getUse());
UsesToRewrite.push_back(&U);
}
// If there are no uses outside the loop, exit with no change.
@@ -208,8 +207,8 @@ bool llvm::formLCSSA(Loop &L, DominatorTree &DT, ScalarEvolution *SE) {
// Reject two common cases fast: instructions with no uses (like stores)
// and instructions with one use that is in the same block as this.
if (I->use_empty() ||
(I->hasOneUse() && I->use_back()->getParent() == BB &&
!isa<PHINode>(I->use_back())))
(I->hasOneUse() && I->user_back()->getParent() == BB &&
!isa<PHINode>(I->user_back())))
continue;
Changed |= processInstruction(L, *I, DT, ExitBlocks, PredCache);