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llvm-project/llvm/test/Analysis/ScalarEvolution/2008-11-18-Stride2.ll

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FileCheck-ize tests. llvm-svn: 188971
2013-08-22 08:51:19 +08:00
; RUN: opt < %s -analyze -scalar-evolution 2>&1 | FileCheck %s
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. llvm-svn: 59528
2008-11-18 23:10:54 +08:00
Rewrite SCEV's backedge taken count computation. Patch by Michele Scandale! Rewrite of the functions used to compute the backedge taken count of a loop on LT and GT comparisons. I decided to split the handling of LT and GT cases becasue the trick "a > b == -a < -b" in some cases prevents the trip count computation due to the multiplication by -1 on the two operands of the comparison. This issue comes from the conservative computation of value range of SCEVs: taking the negative SCEV of an expression that have a small positive range (e.g. [0,31]), we would have a SCEV with a fullset as value range. Indeed, in the new rewritten function I tried to better handle the maximum backedge taken count computation when MAX/MIN expression are used to handle the cases where no entry guard is found. Some test have been modified in order to check the new value correctly (I manually check them and reasoning on possible overflow the new values seem correct). I finally added a new test case related to the multiplication by -1 issue on GT comparisons. llvm-svn: 194116
2013-11-06 10:08:26 +08:00
; CHECK: Loop %bb: backedge-taken count is ((999 + (-1 * %x)) /u 3)
; CHECK: Loop %bb: max backedge-taken count is 334
FileCheck-ize tests. llvm-svn: 188971
2013-08-22 08:51:19 +08:00
Add a comment to this test. llvm-svn: 102387
2010-04-27 05:37:43 +08:00
; This is a tricky testcase for unsigned wrap detection which ScalarEvolution
; doesn't yet know how to do.
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. llvm-svn: 59528
2008-11-18 23:10:54 +08:00
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
}