[ValueTracking] Add tests for knownbits of `abs`; NFC

[RKSimon]

LGTM - we already have the exhaustive tests in KnownBitsTest, but adding explicit test patterns for specific cases is fine.

[goldstein.w.n]

Rebase

[goldstein.w.n]

In D150099#4326321, @RKSimon wrote:

LGTM - we already have the exhaustive tests in KnownBitsTest, but adding explicit test patterns for specific cases is fine.

I see there are two things we want to test. 1) that the knownbits transformations are correct. 2) that is behaves as is expected in valuetracking. Without case 2 we could have a bug that just set all unknown.

[goldstein.w.n]

Rebase

[goldstein.w.n]

Rebase

llvm/test/Analysis/ValueTracking/knownbits-abs.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=instsimplify -S < %s | FileCheck %s
+declare i8 @llvm.abs.i8(i8, i1)
+
+define i1 @abs_low_bit_set(i8 %x) {
+; CHECK-LABEL: @abs_low_bit_set(
+; CHECK-NEXT:    [[XX:%.*]] = and i8 [[X:%.*]], -16
+; CHECK-NEXT:    [[V:%.*]] = or i8 [[XX]], 4
+; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[V]], i1 true)
+; CHECK-NEXT:    [[AND:%.*]] = and i8 [[ABS]], 4
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[AND]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %xx = and i8 %x, 240
+  %v = or i8 %xx, 4
+  %abs = call i8 @llvm.abs.i8(i8 %v, i1 true)
+  %and = and i8 %abs, 4
+  %r = icmp eq i8 %and, 0
+  ret i1 %r
+}
+
+define i1 @abs_unknown_low_bit_set_fail(i8 %x) {
+; CHECK-LABEL: @abs_unknown_low_bit_set_fail(
+; CHECK-NEXT:    [[V:%.*]] = or i8 [[X:%.*]], 2
+; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[V]], i1 true)
+; CHECK-NEXT:    [[AND:%.*]] = and i8 [[ABS]], 2
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[AND]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %v = or i8 %x, 2
+  %abs = call i8 @llvm.abs.i8(i8 %v, i1 true)
+  %and = and i8 %abs, 2
+  %r = icmp eq i8 %and, 0
+  ret i1 %r
+}
+
+define i1 @abs_negative(i8 %x) {
+; CHECK-LABEL: @abs_negative(
+; CHECK-NEXT:    [[XX:%.*]] = and i8 [[X:%.*]], -16
+; CHECK-NEXT:    [[V:%.*]] = or i8 [[XX]], -124
+; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[V]], i1 true)
+; CHECK-NEXT:    [[AND:%.*]] = and i8 [[ABS]], 8
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[AND]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %xx = and i8 %x, 240
+  %v = or i8 %xx, 132
+  %abs = call i8 @llvm.abs.i8(i8 %v, i1 true)
+  %and = and i8 %abs, 8
+  %r = icmp eq i8 %and, 0
+  ret i1 %r
+}
+
+define i1 @abs_negative2(i8 %x) {
+; CHECK-LABEL: @abs_negative2(
+; CHECK-NEXT:    [[V:%.*]] = or i8 [[X:%.*]], -125
+; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[V]], i1 true)
+; CHECK-NEXT:    [[AND:%.*]] = and i8 [[ABS]], 2
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[AND]], 2
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %v = or i8 %x, 131
+  %abs = call i8 @llvm.abs.i8(i8 %v, i1 true)
+  %and = and i8 %abs, 2
+  %r = icmp eq i8 %and, 2
+  ret i1 %r
+}
+
+define i1 @abs_negative_no_carry_info_fail(i8 %x) {
+; CHECK-LABEL: @abs_negative_no_carry_info_fail(
+; CHECK-NEXT:    [[V:%.*]] = or i8 [[X:%.*]], -126
+; CHECK-NEXT:    [[ABS:%.*]] = call i8 @llvm.abs.i8(i8 [[V]], i1 true)
+; CHECK-NEXT:    [[AND:%.*]] = and i8 [[ABS]], 2
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[AND]], 0
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %v = or i8 %x, 130
+  %abs = call i8 @llvm.abs.i8(i8 %v, i1 true)
+  %and = and i8 %abs, 2
+  %r = icmp eq i8 %and, 0
+  ret i1 %r
+}