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[Tests] Add a SCEV analysis test for llvm.widenable.condition

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Mostly because we don't appear to have one and a prototype patch I just saw would have broken the example committed.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@374835 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Philip Reames 2019-10-14 22:42:35 +00:00
parent d6278197e0
commit dc1d7acad3
1 changed files with 45 additions and 0 deletions
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45
test/Analysis/ScalarEvolution/widenable-condition.ll Normal file
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; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
; RUN: opt -analyze -scalar-evolution < %s | FileCheck %s
; The semanics of this example are a bit subtle. The loop is required
; execute some number of times up to 1999. The compiler is free to reduce
; the number of said iterations to zero (or any value in between) if desired,
; but if it does so, the return value and the last value stored to G must
; agree. For SCEV, this translates as widenable conditions preventing exact
; exit counts from being computed, but not restricting max exit counts.
; It's tempting to say that SCEV should return a precise exit count here, but
; would result in miscompiles if transformations such as RLEV ran before
; widening of the WC.
define i32 @wc_max() {
; CHECK-LABEL: 'wc_max'
; CHECK-NEXT: Classifying expressions for: @wc_max
; CHECK-NEXT: %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,1}<%loop> U: [0,2000) S: [0,2000) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = add i32 %iv, 1
; CHECK-NEXT: --> {1,+,1}<%loop> U: [1,2001) S: [1,2001) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %widenable_cond3 = call i1 @llvm.experimental.widenable.condition()
; CHECK-NEXT: --> %widenable_cond3 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %exiplicit_guard_cond4 = and i1 %cond_1, %widenable_cond3
; CHECK-NEXT: --> %exiplicit_guard_cond4 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @wc_max
; CHECK-NEXT: Loop %loop: Unpredictable backedge-taken count.
; CHECK-NEXT: Loop %loop: max backedge-taken count is 1999
; CHECK-NEXT: Loop %loop: Unpredictable predicated backedge-taken count.
;
entry:
br label %loop
loop:
%iv = phi i32 [0, %entry], [%iv.next, %loop]
%iv.next = add i32 %iv, 1
store i32 %iv, i32 *@G
%cond_1 = icmp slt i32 %iv.next, 2000
%widenable_cond3 = call i1 @llvm.experimental.widenable.condition()
%exiplicit_guard_cond4 = and i1 %cond_1, %widenable_cond3
br i1 %exiplicit_guard_cond4, label %loop, label %exit
exit:
ret i32 %iv
}
@G = external global i32
declare i1 @llvm.experimental.widenable.condition()