Type demotion of induction variable for address calculation

Hi all
      I wish to explore the scenarios when the type of an induction
variable used say to index A[i[ in a loop can be demoted to a short.
The motivation being it would aid in an efficient code using 16 bit
multiplies instead of needing 32 bit multiplies for the target.




So far I can see the following cases
1. Size of A is less than 2^32 and assuming the source does not do out
of array access. Does c99 provide such guarrantees ?


2. the maximum value of i is less that 2^16/ sizeof(A[i])
Size of A[i] is size of element.


Is my reasoning valid ? And are there other scenarios ?


Also can some one point to me any such existing work ?


thanks
shrey

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