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llvm-mirror/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ule-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

227 lines
6.5 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 u<= x & C
; Should be transformed into:
; x u<= C
; Iff: isPowerOf2(C + 1)
; C can be 0 and -1.
declare i8 @gen8()
declare <2 x i8> @gen2x8()
declare <3 x i8> @gen3x8()
; ============================================================================ ;
; Basic positive tests
; ============================================================================ ;
define i1 @p0() {
; CHECK-LABEL: @p0(
; 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 ule i8 %x, %tmp0
ret i1 %ret
}
define i1 @pv(i8 %y) {
; CHECK-LABEL: @pv(
; 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 ule i8 %x, %tmp1
ret i1 %ret
}
; ============================================================================ ;
; Vector tests
; ============================================================================ ;
define <2 x i1> @p1_vec_splat() {
; CHECK-LABEL: @p1_vec_splat(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <2 x i8> [[X]], <i8 4, i8 4>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 3>
%ret = icmp ule <2 x i8> %x, %tmp0
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat() {
; CHECK-LABEL: @p2_vec_nonsplat(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <2 x i8> [[X]], <i8 4, i8 16>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 15> ; doesn't have to be splat.
%ret = icmp ule <2 x i8> %x, %tmp0
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat_edgecase0() {
; CHECK-LABEL: @p2_vec_nonsplat_edgecase0(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X]], <i8 3, i8 0>
; CHECK-NEXT: [[RET:%.*]] = icmp ule <2 x i8> [[X]], [[TMP0]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 0>
%ret = icmp ule <2 x i8> %x, %tmp0
ret <2 x i1> %ret
}
define <2 x i1> @p2_vec_nonsplat_edgecase1() {
; CHECK-LABEL: @p2_vec_nonsplat_edgecase1(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
; CHECK-NEXT: [[TMP1:%.*]] = icmp ule <2 x i8> [[X]], <i8 3, i8 -1>
; CHECK-NEXT: ret <2 x i1> [[TMP1]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 -1>
%ret = icmp ule <2 x i8> %x, %tmp0
ret <2 x i1> %ret
}
define <3 x i1> @p3_vec_splat_undef() {
; CHECK-LABEL: @p3_vec_splat_undef(
; CHECK-NEXT: [[X:%.*]] = call <3 x i8> @gen3x8()
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%x = call <3 x i8> @gen3x8()
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
%ret = icmp ule <3 x i8> %x, %tmp0
ret <3 x i1> %ret
}
; ============================================================================ ;
; Commutativity tests.
; ============================================================================ ;
define i1 @c0(i8 %x) {
; CHECK-LABEL: @c0(
; CHECK-NEXT: ret i1 true
;
%tmp0 = and i8 %x, 3
%ret = icmp ule i8 %tmp0, %x ; 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 %tmp0, %x ; swapped order
%ret = icmp ule i8 %x, %tmp1
ret i1 %ret
}
define i1 @cv1(i8 %y) {
; CHECK-LABEL: @cv1(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: ret i1 true
;
%x = call i8 @gen8()
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %x, %tmp0
%ret = icmp ule i8 %tmp1, %x ; swapped order
ret i1 %ret
}
define i1 @cv2(i8 %x, i8 %y) {
; CHECK-LABEL: @cv2(
; CHECK-NEXT: ret i1 true
;
%tmp0 = lshr i8 -1, %y
%tmp1 = and i8 %tmp0, %x ; swapped order
%ret = icmp ule i8 %tmp1, %x ; swapped order
ret i1 %ret
}
; ============================================================================ ;
; One-use tests. We don't care about multi-uses here.
; ============================================================================ ;
declare void @use8(i8)
define i1 @oneuse0() {
; CHECK-LABEL: @oneuse0(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; 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]]
;
%x = call i8 @gen8()
%tmp0 = and i8 %x, 3
call void @use8(i8 %tmp0)
%ret = icmp ule i8 %x, %tmp0
ret i1 %ret
}
; ============================================================================ ;
; Negative tests
; ============================================================================ ;
define i1 @n0() {
; CHECK-LABEL: @n0(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X]], 4
; CHECK-NEXT: [[RET:%.*]] = icmp ule i8 [[X]], [[TMP0]]
; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = and i8 %x, 4 ; power-of-two, but invalid.
%ret = icmp ule i8 %x, %tmp0
ret i1 %ret
}
define i1 @n1(i8 %y, i8 %notx) {
; CHECK-LABEL: @n1(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen8()
; CHECK-NEXT: [[TMP0:%.*]] = and i8 [[X]], 3
; CHECK-NEXT: [[RET:%.*]] = icmp ule i8 [[TMP0]], [[NOTX:%.*]]
; CHECK-NEXT: ret i1 [[RET]]
;
%x = call i8 @gen8()
%tmp0 = and i8 %x, 3
%ret = icmp ule i8 %tmp0, %notx ; not %x
ret i1 %ret
}
define <2 x i1> @n2() {
; CHECK-LABEL: @n2(
; CHECK-NEXT: [[X:%.*]] = call <2 x i8> @gen2x8()
; CHECK-NEXT: [[TMP0:%.*]] = and <2 x i8> [[X]], <i8 3, i8 16>
; CHECK-NEXT: [[RET:%.*]] = icmp ule <2 x i8> [[X]], [[TMP0]]
; CHECK-NEXT: ret <2 x i1> [[RET]]
;
%x = call <2 x i8> @gen2x8()
%tmp0 = and <2 x i8> %x, <i8 3, i8 16> ; only the first one is valid.
%ret = icmp ule <2 x i8> %x, %tmp0
ret <2 x i1> %ret
}