[llvm] [LoopInterchange] Remove 'I' dependency (PR #140709)

[Ryotaro Kasuga via llvm-commits]

================
@@ -0,0 +1,93 @@
+; REQUIRES: asserts
+; RUN: opt < %s -passes=loop-interchange -verify-dom-info -verify-loop-info \
+; RUN:     -disable-output -debug 2>&1 | FileCheck %s
+
+;; In the following case, p0 and p1 may alias, so the direction vector must be [* *].
+;;
+;; void may_alias(float *p0, float *p1) {
+;;   for (int i = 0; i < 4; i++)
+;;     for (int j = 0; j < 4; j++)
+;;       p0[4 * i + j] = p1[4 * j + i];
+;; }
+
+; CHECK:      Dependency matrix before interchange:
+; CHECK-NEXT: * *
+; CHECK-NEXT: Processing InnerLoopId = 1 and OuterLoopId = 0
+define void @may_alias(ptr %p0, ptr %p1) {
+entry:
+  br label %for.i.header
+
+for.i.header:
+  %i = phi i32 [ 0, %entry ], [ %i.inc, %for.i.latch ]
+  br label %for.j
+
+for.j:
+  %j = phi i32 [ 0, %for.i.header ], [ %j.inc, %for.j ]
+  %idx.0 = getelementptr inbounds [4 x [4 x float]], ptr %p0, i32 0, i32 %j, i32 %i
+  %idx.1 = getelementptr inbounds [4 x [4 x float]], ptr %p1, i32 0, i32 %i, i32 %j
+  %0 = load float, ptr %idx.0, align 4
+  store float %0, ptr %idx.1, align 4
+  %j.inc = add nuw nsw i32 %j, 1
+  %cmp.j = icmp slt i32 %j.inc, 4
+  br i1 %cmp.j, label %for.j, label %for.i.latch
+
+for.i.latch:
+  %i.inc = add nuw nsw i32 %i, 1
+  %cmp.i = icmp slt i32 %i.inc, 4
+  br i1 %cmp.i, label %for.i.header, label %exit
+
+exit:
+  ret void
+}
+
+ at A = global [4 x [4 x [4 x float]]] zeroinitializer, align 4
+ at V = global [4 x float] zeroinitializer, align 4
+
+;; In the following case, there is an all direction dependence for the j-loop
+;; and k-loop.
+;;
+;; for (int i = 0; i < 4; i++)
+;;   for (int j = 0; j < 4; j++)
+;;     for (int k = 0; k < 4; k++)
+;;       V[i] += A[i][j][k];
+
+; CHECK:      Dependency matrix before interchange:
+; CHECK-NEXT: = * *
+; CHECK-NEXT: Processing InnerLoopId = 2 and OuterLoopId = 1
+define void @partial_reduction() {
----------------
kasuga-fj wrote:

I misunderstood, but this case has been working correctly so far.

https://github.com/llvm/llvm-project/pull/140709