[LAA] Add test that shows MaxSafeDepDistBytes is incorrect. NFC.

[michaelmaitland]

Summary

This precommit patch shows MaxSafeDepBytesDist is 24 when it should
be 8.

[ABataev]

llvm/test/Analysis/LoopAccessAnalysis/max_safe_dep_dist_non_unit_stride.ll

11–58

Could you try to remove not necessary param attributes and simplify names of basic blocks, vars, etc.?

[michaelmaitland]

Remove not necessary param attributes and simplify names of basic blocks, vars, etc.

[fhahn]

llvm/test/Analysis/LoopAccessAnalysis/max_safe_dep_dist_non_unit_stride.ll

29

is this needed?

30

simpler to pass %len as i64

33

nit: can simply be loop

34

nit: strip indvars.

35

maybe easier to read if this would be %iv.4, same for the other increments

50

nit: can simply be exit

[michaelmaitland]

Cleanup test some more

[michaelmaitland]

llvm/test/Analysis/LoopAccessAnalysis/max_safe_dep_dist_non_unit_stride.ll

29

What do you have in mind to guard entrance into loop when len <= 0?

[fhahn]

Thanks for the updates! It looks like the check lines may need updating ,as the test appears to fail in precommit CI?

llvm/test/Analysis/LoopAccessAnalysis/max_safe_dep_dist_non_unit_stride.ll

29

I think the guard is not needed?

[michaelmaitland]

Remove guard, fix check statements

[fhahn]

LGTM, thanks!

llvm/test/Analysis/LoopAccessAnalysis/max_safe_dep_dist_non_unit_stride.ll

+; RUN: opt -S -disable-output -passes='print<access-info>' < %s 2>&1 | FileCheck %s
+
+; Generated from following C program:
+; void foo(int len, int *a) {
+;   for (int k = 0; k < len; k+=3) {
+;     a[k] = a[k + 4];
+;     a[k+2] = a[k+6];
+;   }
+; }
+define void @foo(i64  %len, ptr %a) {
+; CHECK-LABEL: Loop access info in function 'foo':
+; CHECK-NEXT:  for.body:
+; CHECK-NEXT:    Memory dependences are safe with a maximum dependence distance of 24 bytes
+; CHECK-NEXT:    Dependences:
+; CHECK-NEXT:      BackwardVectorizable:
+; CHECK-NEXT:          store i32 %2, ptr %arrayidx2, align 4 ->
+; CHECK-NEXT:          %4 = load i32, ptr %arrayidx5, align 4
+; CHECK-EMPTY:
+; CHECK-NEXT:    Run-time memory checks:
+; CHECK-NEXT:    Grouped accesses:
+; CHECK-EMPTY:
+; CHECK-NEXT:    Non vectorizable stores to invariant address were not found in loop.
+; CHECK-NEXT:    SCEV assumptions:
+; CHECK-EMPTY:
+; CHECK-NEXT:    Expressions re-written:
+;
+entry:
+  %cmp18 = icmp sgt i64 %len, 0
+  br i1 %cmp18, label %loop.preheader, label %exit
+
+loop.preheader:
+  br label %loop
+
+loop.exit:
+  br label %exit
+
+exit:
+  ret void
+
+loop:
+  %iv = phi i64 [ 0, %loop.preheader ], [ %iv.next, %loop ]
+  %iv.4 = add nuw nsw i64 %iv, 4
+  %arrayidx = getelementptr inbounds i32, ptr %a, i64 %iv.4
+  %0 = load i32, ptr %arrayidx, align 4
+  %arrayidx2 = getelementptr inbounds i32, ptr %a, i64 %iv
+  store i32 %0, ptr %arrayidx2, align 4
+  %iv.6 = add nuw nsw i64 %iv, 6
+  %arrayidx5 = getelementptr inbounds i32, ptr %a, i64 %iv.6
+  %1 = load i32, ptr %arrayidx5, align 4
+  %iv.2 = add nuw nsw i64 %iv, 2
+  %arrayidx8 = getelementptr inbounds i32, ptr %a, i64 %iv.2
+  store i32 %1, ptr %arrayidx8, align 4
+  %iv.next = add nuw nsw i64 %iv, 3
+  %cmp = icmp ult i64 %iv.next, %len
+  br i1 %cmp, label %loop, label %loop.exit
+}