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llvm-6502/test/Analysis/ScalarEvolution/2008-11-18-Stride2.ll
Nick Lewycky dd643f26c4 Add a utility function that detects whether a loop is guaranteed to be finite.
Use it to safely handle less-than-or-equals-to exit conditions in loops. These
also occur when the loop exit branch is exit on true because SCEV inverses the
icmp predicate.

Use it again to handle non-zero strides, but only with an unsigned comparison
in the exit condition.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59528 91177308-0d34-0410-b5e6-96231b3b80d8
2008-11-18 15:10:54 +00:00

31 lines
940 B
LLVM

; RUN: llvm-as < %s | opt -analyze -scalar-evolution |& grep {/u 3}
define i32 @f(i32 %x) nounwind readnone {
entry:
%0 = icmp ugt i32 %x, 999 ; <i1> [#uses=1]
br i1 %0, label %bb2, label %bb.nph
bb.nph: ; preds = %entry
br label %bb
bb: ; preds = %bb.nph, %bb1
%indvar = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb1 ] ; <i32> [#uses=2]
%tmp = mul i32 %indvar, 3 ; <i32> [#uses=1]
%x_addr.04 = add i32 %tmp, %x ; <i32> [#uses=1]
%1 = add i32 %x_addr.04, 3 ; <i32> [#uses=2]
br label %bb1
bb1: ; preds = %bb
%2 = icmp ugt i32 %1, 999 ; <i1> [#uses=1]
%indvar.next = add i32 %indvar, 1 ; <i32> [#uses=1]
br i1 %2, label %bb1.bb2_crit_edge, label %bb
bb1.bb2_crit_edge: ; preds = %bb1
%.lcssa = phi i32 [ %1, %bb1 ] ; <i32> [#uses=1]
br label %bb2
bb2: ; preds = %bb1.bb2_crit_edge, %entry
%x_addr.0.lcssa = phi i32 [ %.lcssa, %bb1.bb2_crit_edge ], [ %x, %entry ] ; <i32> [#uses=1]
ret i32 %x_addr.0.lcssa
}