| ; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py |
| ; RUN: opt -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | 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() |