llvm-mirror/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-eq-to-icmp-ule.ll
Sanjay Patel 5b68045419 [InstCombine] make icmp vector canonicalization safe for constant with undef elements
This is a fix for:
https://bugs.llvm.org/show_bug.cgi?id=43730
...and as shown there, we have existing test cases that show potential miscompiles.

We could just bail out for vector constants that contain any undef elements, or we can do as shown here:
allow the transform, but replace the undefs with a safe value.

For most of the tests shown, this results in a full splat constant (no undefs) which is probably a win
for further IR analysis because we conservatively don't match undefs in most cases. Codegen can probably
recover these kinds of undef lanes via demanded elements analysis if that's profitable.

Differential Revision: https://reviews.llvm.org/D69519
2019-10-29 10:58:14 -04:00

212 lines
6.2 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
; https://bugs.llvm.org/show_bug.cgi?id=38123
; Pattern:
; x & C == x
; Should be transformed into:
; x u<= C
; Iff: isPowerOf2(C + 1)
; C can be 0 and -1.
; ============================================================================ ;
; Basic positive tests
; ============================================================================ ;
define i1 @p0(i8 %x) {
; CHECK-LABEL: @p0(
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i8 [[X:%.*]], 4
; CHECK-NEXT: ret i1 [[TMP1]]
;
%tmp0 = and i8 %x, 3
%ret = icmp eq i8 %tmp0, %x
ret i1 %ret
}
define i1 @pv(i8 %x, i8 %y) {
; CHECK-LABEL: @pv(
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp uge i8 [[TMP0]], [[X:%.*]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %tmp0, %x
%ret = icmp eq i8 %tmp1, %x
ret i1 %ret
}
; ============================================================================ ;
; Vector tests
; ============================================================================ ;
define <2 x i1> @p1_vec_splat(<2 x i8> %x) {
; CHECK-LABEL: @p1_vec_splat(
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <2 x i8> [[X:%.*]], <i8 4, i8 4>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 3>
%ret = icmp eq <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat(<2 x i8> %x) {
; CHECK-LABEL: @p2_vec_nonsplat(
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <2 x i8> [[X:%.*]], <i8 4, i8 16>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 15> ; doesn't have to be splat.
%ret = icmp eq <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat_edgecase0(<2 x i8> %x) {
; CHECK-LABEL: @p2_vec_nonsplat_edgecase0(
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X:%.*]], <i8 3, i8 0>
; CHECK-NEXT: [[RET:%.*]] = icmp eq <2 x i8> [[TMP0]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 0>
%ret = icmp eq <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat_edgecase1(<2 x i8> %x) {
; CHECK-LABEL: @p2_vec_nonsplat_edgecase1(
; CHECK-NEXT: [[TMP1:%.*]] = icmp ule <2 x i8> [[X:%.*]], <i8 3, i8 -1>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 -1>
%ret = icmp eq <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}
define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
; CHECK-LABEL: @p3_vec_splat_undef(
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X:%.*]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
%ret = icmp eq <3 x i8> %tmp0, %x
ret <3 x i1> %ret
}
; ============================================================================ ;
; Commutativity tests.
; ============================================================================ ;
declare i8 @gen8()
define i1 @c0() {
; CHECK-LABEL: @c0(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i8 [[X]], 4
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = and i8 %x, 3
%ret = icmp eq i8 %x, %tmp0 ; swapped order
ret i1 %ret
}
; ============================================================================ ;
; Commutativity tests with variable
; ============================================================================ ;
define i1 @cv0(i8 %y) {
; CHECK-LABEL: @cv0(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp ule i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %x, %tmp0 ; swapped order
%ret = icmp eq i8 %tmp1, %x
ret i1 %ret
}
define i1 @cv1(i8 %y) {
; CHECK-LABEL: @cv1(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp ule i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %tmp0, %x
%ret = icmp eq i8 %x, %tmp1 ; swapped order
ret i1 %ret
}
define i1 @cv2(i8 %y) {
; CHECK-LABEL: @cv2(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = icmp ule i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[TMP1]]
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %x, %tmp0 ; swapped order
%ret = icmp eq i8 %x, %tmp1 ; swapped order
ret i1 %ret
}
; ============================================================================ ;
; One-use tests. We don't care about multi-uses here.
; ============================================================================ ;
declare void @use8(i8)
define i1 @oneuse0(i8 %x) {
; CHECK-LABEL: @oneuse0(
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X:%.*]], 3
; CHECK-NEXT: call void @use8(i8 [[TMP0]])
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i8 [[X]], 4
; CHECK-NEXT: ret i1 [[TMP1]]
;
%tmp0 = and i8 %x, 3
call void @use8(i8 %tmp0)
%ret = icmp eq i8 %tmp0, %x
ret i1 %ret
}
; ============================================================================ ;
; Negative tests
; ============================================================================ ;
define i1 @n0(i8 %x) {
; CHECK-LABEL: @n0(
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X:%.*]], 4
; CHECK-NEXT: [[RET:%.*]] = icmp eq i8 [[TMP0]], [[X]]
; CHECK-NEXT: ret i1 [[RET]]
;
%tmp0 = and i8 %x, 4 ; power-of-two, but invalid.
%ret = icmp eq i8 %tmp0, %x
ret i1 %ret
}
define i1 @n1(i8 %x, i8 %y, i8 %notx) {
; CHECK-LABEL: @n1(
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X:%.*]], 3
; CHECK-NEXT: [[RET:%.*]] = icmp eq i8 [[TMP0]], [[NOTX:%.*]]
; CHECK-NEXT: ret i1 [[RET]]
;
%tmp0 = and i8 %x, 3
%ret = icmp eq i8 %tmp0, %notx ; not %x
ret i1 %ret
}
define <2 x i1> @n2(<2 x i8> %x) {
; CHECK-LABEL: @n2(
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X:%.*]], <i8 3, i8 16>
; CHECK-NEXT: [[RET:%.*]] = icmp eq <2 x i8> [[TMP0]], [[X]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%tmp0 = and <2 x i8> %x, <i8 3, i8 16> ; only the first one is valid.
%ret = icmp eq <2 x i8> %tmp0, %x
ret <2 x i1> %ret
}