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Teach ScalarEvolution how to compute a tripcount for a loop with

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true or false as its exit condition. These are usually eliminated by
SimplifyCFG, but the may be left around during a pass which wishes
to preserve the CFG.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96683 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-02-19 18:12:07 +00:00
parent 6b89aa57e6
commit 00cb5b7245
10 changed files with 101 additions and 12 deletions
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76
test/Analysis/ScalarEvolution/trip-count10.ll Normal file
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; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
; Trip counts with trivial exit conditions.
; CHECK: Determining loop execution counts for: @a
; CHECK: Loop %loop: Unpredictable backedge-taken count.
; CHECK: Loop %loop: Unpredictable max backedge-taken count.
; CHECK: Determining loop execution counts for: @b
; CHECK: Loop %loop: backedge-taken count is false
; CHECK: Loop %loop: max backedge-taken count is false
; CHECK: Determining loop execution counts for: @c
; CHECK: Loop %loop: backedge-taken count is false
; CHECK: Loop %loop: max backedge-taken count is false
; CHECK: Determining loop execution counts for: @d
; CHECK: Loop %loop: Unpredictable backedge-taken count.
; CHECK: Loop %loop: Unpredictable max backedge-taken count.
define void @a(i64 %n) nounwind {
entry:
%t0 = icmp sgt i64 %n, 0
br i1 %t0, label %loop, label %return
loop:
%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
%i.next = add nsw i64 %i, 1
%exitcond = icmp eq i64 %i.next, %n
br i1 false, label %return, label %loop
return:
ret void
}
define void @b(i64 %n) nounwind {
entry:
%t0 = icmp sgt i64 %n, 0
br i1 %t0, label %loop, label %return
loop:
%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
%i.next = add nsw i64 %i, 1
%exitcond = icmp eq i64 %i.next, %n
br i1 true, label %return, label %loop
return:
ret void
}
define void @c(i64 %n) nounwind {
entry:
%t0 = icmp sgt i64 %n, 0
br i1 %t0, label %loop, label %return
loop:
%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
%i.next = add nsw i64 %i, 1
%exitcond = icmp eq i64 %i.next, %n
br i1 false, label %loop, label %return
return:
ret void
}
define void @d(i64 %n) nounwind {
entry:
%t0 = icmp sgt i64 %n, 0
br i1 %t0, label %loop, label %return
loop:
%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
%i.next = add nsw i64 %i, 1
%exitcond = icmp eq i64 %i.next, %n
br i1 true, label %loop, label %return
return:
ret void
}