Expand GEPs in ScalarEvolution expressions. SCEV expressions can now

have pointer types, though in contrast to C pointer types, SCEV
addition is never implicitly scaled. This not only eliminates the
need for special code like IndVars' EliminatePointerRecurrence
and LSR's own GEP expansion code, it also does a better job because
it lets the normal optimizations handle pointer expressions just
like integer expressions.

Also, since LLVM IR GEPs can't directly index into multi-dimensional
VLAs, moving the GEP analysis out of client code and into the SCEV
framework makes it easier for clients to handle multi-dimensional
VLAs the same way as other arrays.

Some existing regression tests show improved optimization.
test/CodeGen/ARM/2007-03-13-InstrSched.ll in particular improved to
the point where if-conversion started kicking in; I turned it off
for this test to preserve the intent of the test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@69258 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/X86/iv-users-in-other-loops.ll

@@ -1,7 +1,8 @@
 ; RUN: llvm-as < %s | llc -march=x86-64 -f -o %t
 ; RUN: grep inc %t | count 2
 ; RUN: grep addq %t | count 13
-; RUN: grep leaq %t | count 9
+; RUN: grep leaq %t | count 8
+; RUN: grep leal %t | count 4
 ; RUN: grep movq %t | count 5
 
 ; IV users in each of the loops from other loops shouldn't cause LSR