From 2d6aff84c9d7ab7babec3511197337467e3b3082 Mon Sep 17 00:00:00 2001 From: Philip Reames Date: Mon, 3 May 2021 16:22:56 -0700 Subject: [PATCH] One more test case inspired by PR50191 --- .../test/Analysis/ValueTracking/known-non-equal.ll | 38 ++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/llvm/test/Analysis/ValueTracking/known-non-equal.ll b/llvm/test/Analysis/ValueTracking/known-non-equal.ll index 915ecf7..c1a8f07 100644 --- a/llvm/test/Analysis/ValueTracking/known-non-equal.ll +++ b/llvm/test/Analysis/ValueTracking/known-non-equal.ll @@ -1715,6 +1715,7 @@ exit: ret i1 %res } + define i1 @mutual_recurrence_neq(i8 %A) { ; CHECK-LABEL: @mutual_recurrence_neq( ; CHECK-NEXT: entry: @@ -1779,5 +1780,42 @@ exit: ret i1 %res } +; Illustrate a case where A_IV_i == B_IV_i for all i > 0, but A_IV_0 != B_IV_0. +; (E.g. This pair of mutually defined recurrences are not invertible.) +define i1 @recurrence_collapse(i8 %A) { +; CHECK-LABEL: @recurrence_collapse( +; CHECK-NEXT: entry: +; CHECK-NEXT: [[B:%.*]] = add i8 [[A:%.*]], 1 +; CHECK-NEXT: br label [[LOOP:%.*]] +; CHECK: loop: +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ] +; CHECK-NEXT: [[A_IV:%.*]] = phi i8 [ [[A]], [[ENTRY]] ], [ [[A_IV_NEXT:%.*]], [[LOOP]] ] +; CHECK-NEXT: [[B_IV:%.*]] = phi i8 [ [[B]], [[ENTRY]] ], [ [[B_IV_NEXT:%.*]], [[LOOP]] ] +; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1 +; CHECK-NEXT: [[A_IV_NEXT]] = sub i8 [[A_IV]], [[B_IV]] +; CHECK-NEXT: [[B_IV_NEXT]] = sub i8 [[A_IV]], [[B_IV]] +; CHECK-NEXT: [[CMP:%.*]] = icmp ne i64 [[IV_NEXT]], 10 +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]] +; CHECK: exit: +; CHECK-NEXT: [[RES:%.*]] = icmp eq i8 [[A_IV]], [[B_IV]] +; CHECK-NEXT: ret i1 [[RES]] +; +entry: + %B = add i8 %A, 1 + br label %loop +loop: + %iv = phi i64 [0, %entry], [%iv.next, %loop] + %A.iv = phi i8 [%A, %entry], [%A.iv.next, %loop] + %B.iv = phi i8 [%B, %entry], [%B.iv.next, %loop] + %iv.next = add i64 %iv, 1 + %A.iv.next = sub i8 %A.iv, %B.iv + %B.iv.next = sub i8 %A.iv, %B.iv + %cmp = icmp ne i64 %iv.next, 10 + br i1 %cmp, label %loop, label %exit +exit: + %res = icmp eq i8 %A.iv, %B.iv + ret i1 %res +} + !0 = !{ i8 1, i8 5 } -- 2.7.4