[test] Pre-commit test case for PR51981. NFC

[fhahn]

llvm/test/Transforms/LoopRotate/pr51981-scev-problem.ll

3

Just do double check, running loop(canon-freeze) is required for the crash? Is that only so the SCEV cache is populated?

[bjope]

llvm/test/Transforms/LoopRotate/pr51981-scev-problem.ll

3

Yes, that is my understanding. I tried to populate it using print<scalar-evolution> instead, or require<scalar-evolution>, but then I do not see the crash for some reason.
Btw, I noticed right now that I can replace bounds-checking by print<scalar-evolution> and then I still get the crash (but in the printing pass instead).

Not quite sure why the symptom is a bit different depending on how I populate the cache. Afaict canon-freeze isn't doing any modifications to the IR (and neither should the printing).

[fhahn]

llvm/test/Transforms/LoopRotate/pr51981-scev-problem.ll

3

Btw, I noticed right now that I can replace bounds-checking by print<scalar-evolution> and then I still get the crash (but in the printing pass instead).

Using print<scalar-evolution> instead of bounds-checking would be better, as print<scalar-evolution> should be more stable.

36

it might be good to rename the blocks to make it easier to identify that there is a loop nest with 2 loops (maybe something like loop.1.header, loop.2, loop.1.latch)

37

does this have to be a load?

[bjope]

Cleaned up the test case a bit as suggested in the review.

[bjope]

llvm/test/Transforms/LoopRotate/pr51981-scev-problem.ll

37

Haven't found anything else that still reproduce the problem (such as using an add instruction instead).

[fhahn]

LGTM, thanks!

llvm/test/Transforms/LoopRotate/pr51981-scev-problem.ll

+; RUN: opt < %s -passes='print<scalar-evolution>,loop(loop-rotate),invalidate<scalar-evolution>,print<scalar-evolution>' -disable-output 2>&1 | FileCheck -check-prefixes CHECK-SCEV,CHECK-SCEV-OK %s
+; RUN: opt < %s -passes='print<scalar-evolution>,loop(loop-rotate),print<scalar-evolution>' -disable-output 2>&1 | FileCheck -check-prefixes CHECK-SCEV,CHECK-SCEV-NOK %s
+; FIXME (crashes): opt < %s -passes='loop(canon-freeze),loop(loop-rotate),function(bounds-checking)' -disable-output
+
+; Verify that we get the same SCEV expressions after loop-rotate, regardless if we invalidate scalar-evolution before the final printing or not.
+; FIXME: As indicated by CHECK-SCEV-OK vs CHECK-SCEV-NOK this isn't currently true (PR51981).
+;
+; CHECK-SCEV: Classifying expressions for: @test_memcpy_1
+; CHECK-SCEV:   %div210 = load i32, i32* @offset, align 1
+; CHECK-SCEV:   -->  %div210 U: full-set S: full-set          Exits: <<Unknown>>              LoopDispositions: { %for.cond109: Variant, %for.body215: Invariant }
+; CHECK-SCEV:   %conv211 = trunc i32 %div210 to i16
+; CHECK-SCEV:   -->  (trunc i32 %div210 to i16) U: full-set S: full-set               Exits: <<Unknown>>              LoopDispositions: { %for.cond109: Variant, %for.body215: Invariant }
+; CHECK-SCEV:   %inc2243 = phi i16 [ %conv211, %for.body215.lr.ph ], [ %inc224, %for.body215 ]
+; CHECK-SCEV:   -->  {(trunc i32 %div210 to i16),+,1}<%for.body215> U: full-set S: full-set           Exits: (-1 + (700 umax (1 + (trunc i32 %div210 to i16))))               LoopDispositions: { %for.body215: Computable, %for.cond109: Variant }
+;
+; CHECK-SCEV: Classifying expressions for: @test_memcpy_1
+; CHECK-SCEV:   %div2101 = load i32, i32* @offset, align 1
+; CHECK-SCEV:   -->  %div2101 U: full-set S: full-set
+; CHECK-SCEV:   %div2102 = phi i32 [ %div2101, %for.body215.lr.ph.lr.ph ], [ %div210, %crit_edge ]
+; CHECK-SCEV:   -->  %div2102 U: full-set S: full-set         Exits: <<Unknown>>              LoopDispositions: { %for.body215.lr.ph: Variant, %for.body215: Invariant }
+; CHECK-SCEV:   %conv211 = trunc i32 %div2102 to i16
+; CHECK-SCEV-OK:   -->  (trunc i32 %div2102 to i16) U: full-set S: full-set               Exits: <<Unknown>>              LoopDispositions: { %for.body215.lr.ph: Variant, %for.body215: Invariant }
+; CHECK-SCEV-NOK:   -->  (trunc i32 %div210 to i16) U: full-set S: full-set               Exits: <<Unknown>>              LoopDispositions: { %for.body215.lr.ph: Variant, %for.body215: Invariant }
+; CHECK-SCEV:   %inc2243 = phi i16 [ %conv211, %for.body215.lr.ph ], [ %inc224, %for.body215 ]
+; CHECK-SCEV-OK:   -->  {(trunc i32 %div2102 to i16),+,1}<%for.body215> U: full-set S: full-set           Exits: (-1 + (700 umax (1 + (trunc i32 %div2102 to i16))))               LoopDispositions: { %for.body215: Computable, %for.body215.lr.ph: Variant }
+; CHECK-SCEV-NOK:   -->  {(trunc i32 %div210 to i16),+,1}<%for.body215> U: full-set S: full-set           Exits: (-1 + (700 umax (1 + (trunc i32 %div210 to i16))))               LoopDispositions: { %for.body215: Computable, %for.body215.lr.ph: Variant }
+
+
+@offset = external dso_local global i32, align 1
+@cm_array = internal global [11263 x i32] zeroinitializer, align 1
+
+define void @test_memcpy_1(i1 %a) {
+entry:
+  br label %for.cond109
+
+for.cond109:                                      ; preds = %crit_edge, %entry
+  %div210 = load i32, i32* @offset, align 1
+  br i1 %a, label %exit, label %for.body215.lr.ph
+
+for.body215.lr.ph:                                ; preds = %for.cond109
+  %conv211 = trunc i32 %div210 to i16
+  br label %for.body215
+
+for.body215:                                      ; preds = %for.body215, %for.body215.lr.ph
+  %inc2243 = phi i16 [ %conv211, %for.body215.lr.ph ], [ %inc224, %for.body215 ]
+  %idxprom221 = zext i16 %inc2243 to i32
+  %arrayidx222 = getelementptr inbounds [11263 x i32], [11263 x i32]* @cm_array, i32 0, i32 %idxprom221
+  store i32 7, i32* %arrayidx222, align 1
+  %inc224 = add i16 %inc2243, 1
+  %cmp213 = icmp ult i16 %inc224, 700
+  br i1 %cmp213, label %for.body215, label %crit_edge
+
+crit_edge:                                        ; preds = %for.body215
+  br label %for.cond109
+
+exit:                                             ; preds = %for.cond109
+  ret void
+}
+