[Tests] Add a SCEV analysis test for llvm.widenable.condition
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
diff --git a/test/Analysis/ScalarEvolution/widenable-condition.ll b/test/Analysis/ScalarEvolution/widenable-condition.ll
new file mode 100644
index 0000000..b7b5f71
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/widenable-condition.ll
@@ -0,0 +1,45 @@
+; 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()
