[ARM,MVE] Add an InstCombine rule permitting VPNOT.

Summary:
If a user writing C code using the ACLE MVE intrinsics generates a
predicate and then complements it, then the resulting IR will use the
`pred_v2i` IR intrinsic to turn some `<n x i1>` vector into a 16-bit
integer; complement that integer; and convert back. This will generate
machine code that moves the predicate out of the `P0` register,
complements it in an integer GPR, and moves it back in again.

This InstCombine rule replaces `i2v(~v2i(x))` with a direct complement
of the original predicate vector, which we can already instruction-
select as the VPNOT instruction which complements P0 in place.

Reviewers: ostannard, MarkMurrayARM, dmgreen

Reviewed By: dmgreen

Subscribers: kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70484

1 files changed, 94 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/ARM/mve-v2i2v.ll b/llvm/test/Transforms/InstCombine/ARM/mve-v2i2v.ll
index 4594102a468..7c511135ba1 100644
--- a/llvm/test/Transforms/InstCombine/ARM/mve-v2i2v.ll
+++ b/llvm/test/Transforms/InstCombine/ARM/mve-v2i2v.ll
@@ -1,6 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -instcombine -S -o - %s | FileCheck %s
 
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+
 declare i32 @llvm.arm.mve.pred.v2i.v4i1(<4 x i1>)
 declare i32 @llvm.arm.mve.pred.v2i.v8i1(<8 x i1>)
 declare i32 @llvm.arm.mve.pred.v2i.v16i1(<16 x i1>)
@@ -234,3 +236,95 @@ entry:
   %vout = call <4 x i1> @llvm.arm.mve.pred.i2v.v4i1(i32 %wide2)
   ret <4 x i1> %vout
 }
+
+; If a predicate vector is round-tripped to an integer and back, and
+; complemented while it's in integer form, we should collapse that to
+; a complement of the vector itself. (Rationale: this is likely to
+; allow it to be code-generated as MVE VPNOT.)
+
+define <4 x i1> @vpnot_4(<4 x i1> %vin) {
+; CHECK-LABEL: @vpnot_4(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[VOUT:%.*]] = xor <4 x i1> [[VIN:%.*]], <i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    ret <4 x i1> [[VOUT]]
+;
+entry:
+  %int = call i32 @llvm.arm.mve.pred.v2i.v4i1(<4 x i1> %vin)
+  %flipped = xor i32 %int, 65535
+  %vout = call <4 x i1> @llvm.arm.mve.pred.i2v.v4i1(i32 %flipped)
+  ret <4 x i1> %vout
+}
+
+define <8 x i1> @vpnot_8(<8 x i1> %vin) {
+; CHECK-LABEL: @vpnot_8(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[VOUT:%.*]] = xor <8 x i1> [[VIN:%.*]], <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    ret <8 x i1> [[VOUT]]
+;
+entry:
+  %int = call i32 @llvm.arm.mve.pred.v2i.v8i1(<8 x i1> %vin)
+  %flipped = xor i32 %int, 65535
+  %vout = call <8 x i1> @llvm.arm.mve.pred.i2v.v8i1(i32 %flipped)
+  ret <8 x i1> %vout
+}
+
+define <16 x i1> @vpnot_16(<16 x i1> %vin) {
+; CHECK-LABEL: @vpnot_16(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[VOUT:%.*]] = xor <16 x i1> [[VIN:%.*]], <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    ret <16 x i1> [[VOUT]]
+;
+entry:
+  %int = call i32 @llvm.arm.mve.pred.v2i.v16i1(<16 x i1> %vin)
+  %flipped = xor i32 %int, 65535
+  %vout = call <16 x i1> @llvm.arm.mve.pred.i2v.v16i1(i32 %flipped)
+  ret <16 x i1> %vout
+}
+
+; And this still works even if the i32 is narrowed to i16 and back on
+; opposite sides of the xor.
+
+define <4 x i1> @vpnot_narrow_4(<4 x i1> %vin) {
+; CHECK-LABEL: @vpnot_narrow_4(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[VOUT:%.*]] = xor <4 x i1> [[VIN:%.*]], <i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    ret <4 x i1> [[VOUT]]
+;
+entry:
+  %int = call i32 @llvm.arm.mve.pred.v2i.v4i1(<4 x i1> %vin)
+  %narrow = trunc i32 %int to i16
+  %flipped_narrow = xor i16 %narrow, -1
+  %flipped = zext i16 %flipped_narrow to i32
+  %vout = call <4 x i1> @llvm.arm.mve.pred.i2v.v4i1(i32 %flipped)
+  ret <4 x i1> %vout
+}
+
+define <8 x i1> @vpnot_narrow_8(<8 x i1> %vin) {
+; CHECK-LABEL: @vpnot_narrow_8(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[VOUT:%.*]] = xor <8 x i1> [[VIN:%.*]], <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    ret <8 x i1> [[VOUT]]
+;
+entry:
+  %int = call i32 @llvm.arm.mve.pred.v2i.v8i1(<8 x i1> %vin)
+  %narrow = trunc i32 %int to i16
+  %flipped_narrow = xor i16 %narrow, -1
+  %flipped = zext i16 %flipped_narrow to i32
+  %vout = call <8 x i1> @llvm.arm.mve.pred.i2v.v8i1(i32 %flipped)
+  ret <8 x i1> %vout
+}
+
+define <16 x i1> @vpnot_narrow_16(<16 x i1> %vin) {
+; CHECK-LABEL: @vpnot_narrow_16(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[VOUT:%.*]] = xor <16 x i1> [[VIN:%.*]], <i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    ret <16 x i1> [[VOUT]]
+;
+entry:
+  %int = call i32 @llvm.arm.mve.pred.v2i.v16i1(<16 x i1> %vin)
+  %narrow = trunc i32 %int to i16
+  %flipped_narrow = xor i16 %narrow, -1
+  %flipped = zext i16 %flipped_narrow to i32
+  %vout = call <16 x i1> @llvm.arm.mve.pred.i2v.v16i1(i32 %flipped)
+  ret <16 x i1> %vout
+}