[PATCH] Handle big index in getelementptr instruction

[Paweł Bylica]

REPOSITORY
  rL LLVM

================
Comment at: lib/CodeGen/SelectionDAG/FastISel.cpp:521
@@ -520,3 +520,3 @@
         // N = N + Offset
-        TotalOffs +=
-            DL.getTypeAllocSize(Ty) * cast<ConstantInt>(CI)->getSExtValue();
+        auto I = CI->getValue().sextOrTrunc(sizeof(TotalOffs)*8).getSExtValue();
+        TotalOffs += DL.getTypeAllocSize(Ty) * I;
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majnemer wrote:
> chfast wrote:
> > rnk wrote:
> > > rnk wrote:
> > > > Don't shadow the outer 'I' variable.
> > > This sizeof computation doesn't get PtrSize. LLVM is a cross compiler. You can compute it out of the loop.
> > I don't want a PtrSize, I want TotalOffs size in bits, because I'm going to add to that variable.
> In that case, please just use 64.  LLVM assumes that pointers are not wider than 64-bits.
> 
> Is this functionally different from:
>   CI->getValue().trunc(64).getSExtValue();
> 
> ?
It is different. `CI->getValue()` can be also smaller than i64, e.g i8. We need to sext if smaller, trunc if bigger.

http://reviews.llvm.org/D8219

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