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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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4
lib/Transforms/Scalar/TailRecursionElimination.cpp
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@@ -380,13 +380,13 @@ Value *TailCallElim::CanTransformAccumulatorRecursion(Instruction *I,
return 0;
// The only user of this instruction we allow is a single return instruction.
if (!I->hasOneUse() || !isa<ReturnInst>(I->use_back()))
if (!I->hasOneUse() || !isa<ReturnInst>(I->user_back()))
return 0;
// Ok, now we have to check all of the other return instructions in this
// function. If they return non-constants or differing values, then we cannot
// transform the function safely.
return getCommonReturnValue(cast<ReturnInst>(I->use_back()), CI);
return getCommonReturnValue(cast<ReturnInst>(I->user_back()), CI);
}
static Instruction *FirstNonDbg(BasicBlock::iterator I) {