[PATCH] [SLSR] handle candidate form &B[i * S]

[Jingyue Wu]

================
Comment at: lib/Transforms/Scalar/StraightLineStrengthReduce.cpp:259
@@ +258,3 @@
+    // non-free computation.
+    if (TTI && isCompletelyFoldable(GEP, TTI, DL))
+      return;
----------------
hfinkel wrote:
> We always have TTI, you don't need to check for it.
Thanks. I missed this one. 

================
Comment at: lib/Transforms/Scalar/StraightLineStrengthReduce.cpp:272
@@ -168,3 +271,3 @@
     if (isBasisFor(*Basis, C)) {
       C.Basis = &(*Basis);
       break;
----------------
hfinkel wrote:
> If Basis.Basis != nullptr, do we want to set C.Basis to that?
> 
Yes. In that case, C.Ins can still be rewritten with respect to Basis.Ins. For example, 
```
... &a[s]; // Basis. Assume this is the first memory reference to a, so Basis.Basis == nullptr. 
... &a[s * 2]; // C. We still want to rewrite C to Basis + s.
```

================
Comment at: lib/Transforms/Scalar/StraightLineStrengthReduce.cpp:465
@@ +464,3 @@
+        unsigned AS =
+            cast<PointerType>(Basis.Ins->getType())->getAddressSpace();
+        Type *CharTy = Type::getInt8PtrTy(Basis.Ins->getContext(), AS);
----------------
hfinkel wrote:
> This can be just:
> 
>   unsigned AS = Basis.Ins->getType()->getPointerAddressSpace();
Thanks! 

================
Comment at: lib/Transforms/Scalar/StraightLineStrengthReduce.cpp:503
@@ -251,3 +502,3 @@
     BasicBlock *B = node->getBlock();
     for (auto I = B->begin(); I != B->end(); ++I) {
       allocateCandidateAndFindBasis(I);
----------------
hfinkel wrote:
> Use range-based for.
I may be missing something, but I don't see any API of BasicBlock that returns an iterator_range. 
http://llvm.org/docs/doxygen/html/classllvm_1_1BasicBlock.html

http://reviews.llvm.org/D7459

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