[WebAssembly] SIMD extract_lane

[tlively]

Summary

Implement instruction selection for all versions of the extract_lane
instruction. Use explicit sext/zext to differentiate between
extract_lane_s and extract_lane_u for applicable types, otherwise
default to extract_lane_u.

Patch by Thomas Lively

[aheejin]

Looks good

lib/Target/WebAssembly/WebAssemblyInstrSIMD.td

18

Question: How does "#SIZE#" turn it into a number?

22

Is a default value on an argument meaningful when some of subsequent parameters don't have defaults?

34

Looks like vector_extract is deprecated and [[ https://github.com/llvm-mirror/llvm/blob/a297d9641672dda1e268ec23d83387a4d42042ff/include/llvm/Target/TargetSelectionDAG.td#L404 | extractelt ]] is preferred. For other uses as well.

75

If we don't have these, do they not get selected?

[tlively]

lib/Target/WebAssembly/WebAssemblyInstrSIMD.td

18

# is like a superpowered strconcat in TableGen. In this case it casts SIZE from an int to a string then appends it to the LaneIdx identifier.

22

Nope, this slipped through a refactoring. Thanks!

34

It doesn't seem to be a drop-in replacement, though. When I replace vector_extract with extractelt I get a TableGen compilation error: Type set is empty for each HW mode: possible type contradiction in the pattern below. The pattern is EXTRACT_LANE_S_I8x16: (sext_inreg:{ *:[i32] } (extractelt:{ *:[] } V128:{ *:[] }:$vec, (imm:{ *:[i32] })<<P:Predicate_LaneIdx16>>:$idx), i8:{ *:[Other] })

75

That's correct. Without these patterns you just get a selection error without an explicit extension.

[tlively]

• Remove useless default arg

[aheejin]

lib/Target/WebAssembly/WebAssemblyInstrSIMD.td

34

Hmm, looks like extractelt has [[ https://github.com/llvm-mirror/llvm/blob/e747ac6d9aaaf2d02c3d0a6772285737ea4f08a3/include/llvm/Target/TargetSelectionDAG.td#L241-L243 | SDVecExtract ]] has SDTCisEltOfVec<0, 1> property that's not in vector_extract and it's causing the failure. Looks like, under this property, the result should be the same with the element type of the first argument, which means, i32 = extractelt i8v16 v imm wouldn't work, and I guess that's the reason.

Anyway, vector_extract is still being used widely in LLVM, so I guess that'd be OK.

75

About what we talked in person: I was wondering if scalar loads would have similar rules, but it turned out they do. So nevermind.

[aheejin]

test/CodeGen/WebAssembly/simd.ll

1

Can you remove -wasm-register-codegen-test-mode in this and the other CL? rL339474 was reverted, so we don't have that option yet.

[tlively]

• Remove useless default arg
• Fix llc args in test

lib/Target/WebAssembly/WebAssemblyInstrSIMD.td

 // WebAssemblyInstrSIMD.td - WebAssembly SIMD codegen support -*- tablegen -*-//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// WebAssembly SIMD operand code-gen constructs.
 ///
 //===----------------------------------------------------------------------===//
 
+// Immediate argument types
+def ImmByte : ImmLeaf<i32, [{ return 0 <= Imm && Imm < 256; }]>;
+foreach SIZE = [2, 4, 8, 16, 32] in
+def LaneIdx#SIZE : ImmLeaf<i32, "return 0 <= Imm && Imm < "#SIZE#";">;
+
+// lane extraction
+multiclass ExtractLane<ValueType vec_t, ImmLeaf imm_t,
+                       WebAssemblyRegClass reg_t, string name, bits<32> simdop,
+                       SDNode extract = vector_extract> {
+  defm "" : SIMD_I<(outs reg_t:$dst), (ins V128:$vec, I32:$idx),
+                   (outs), (ins I32:$idx),
+                   [(set reg_t:$dst,
+                     (extract (vec_t V128:$vec), (i32 imm_t:$idx)))],
+                   name#"\t$dst, $vec, $idx", name#"\t$idx", simdop>;
+}
+multiclass ExtractPat<ValueType lane_t, int mask> {
+  def _s : PatFrag<(ops node:$vec, node:$idx),
+                   (i32 (sext_inreg
+                     (i32 (vector_extract
+                       node:$vec,
+                       node:$idx
+                     )),
+                     lane_t
+                   ))>;
+  def _u : PatFrag<(ops node:$vec, node:$idx),
+                   (i32 (and
+                     (i32 (vector_extract
+                       node:$vec,
+                       node:$idx
+                     )),
+                     (i32 mask)
+                   ))>;
+}
+defm extract_i8x16 : ExtractPat<i8, 0xff>;
+defm extract_i16x8 : ExtractPat<i16, 0xffff>;
+multiclass ExtractLaneExtended<string sign, bits<32> baseInst> {
+  defm _I8x16 : ExtractLane<v16i8, LaneIdx16, I32, "i8x16.extract_lane"#sign,
+                            baseInst, !cast<PatFrag>("extract_i8x16"#sign)>;
+  defm _I16x8 : ExtractLane<v8i16, LaneIdx8, I32, "i16x8.extract_lane"#sign,
+                            !add(baseInst, 2),
+                            !cast<PatFrag>("extract_i16x8"#sign)>;
+}
+
 let Defs = [ARGUMENTS] in {
+defm EXTRACT_LANE_S : ExtractLaneExtended<"_s", 9>;
+defm EXTRACT_LANE_U : ExtractLaneExtended<"_u", 10>;
+defm EXTRACT_LANE_I32x4 :
+    ExtractLane<v4i32, LaneIdx4, I32, "i32x4.extract_lane", 13>;
+defm EXTRACT_LANE_I64x2 :
+    ExtractLane<v2i64, LaneIdx2, I64, "i64x2.extract_lane", 14>;
+defm EXTRACT_LANE_F32x4 :
+    ExtractLane<v4f32, LaneIdx4, F32, "f32x4.extract_lane", 15>;
+defm EXTRACT_LANE_F64x2 :
+    ExtractLane<v2f64, LaneIdx2, F64, "f64x2.extract_lane", 16>;
+} // Defs = [ARGUMENTS]
+
+// follow convention of making implicit expansions unsigned
+def : Pat<(i32 (vector_extract (v16i8 V128:$vec), (i32 LaneIdx16:$idx))),
+          (EXTRACT_LANE_U_I8x16 V128:$vec, (i32 LaneIdx16:$idx))>;
+def : Pat<(i32 (vector_extract (v8i16 V128:$vec), (i32 LaneIdx8:$idx))),
+          (EXTRACT_LANE_U_I16x8 V128:$vec, (i32 LaneIdx8:$idx))>;
 
+// arithmetic
+let Defs = [ARGUMENTS] in {
 let isCommutable = 1 in
 defm ADD : SIMDBinaryInt<add, "add ", 24>;
 defm SUB : SIMDBinaryInt<sub, "sub ", 28>;
 let isCommutable = 1 in
 defm MUL : SIMDBinaryInt<mul, "mul ", 32>;
-
 let isCommutable = 1 in
 defm ADD : SIMDBinaryFP<fadd, "add ", 122>;
 defm SUB : SIMDBinaryFP<fsub, "sub ", 124>;
 defm DIV : SIMDBinaryFP<fdiv, "div ", 126>;
 let isCommutable = 1 in
 defm MUL : SIMDBinaryFP<fmul, "mul ", 128>;
-
 } // Defs = [ARGUMENTS]

test/CodeGen/WebAssembly/simd.ll

+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-register-codegen-test-mode -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-register-codegen-test-mode -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128-VM
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-register-codegen-test-mode -mattr=-simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+
+; Test that basic SIMD128 vector manipulation operations assemble as expected.
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown"
+
+; ==============================================================================
+; 16 x i8
+; ==============================================================================
+; CHECK-LABEL: extract_v16i8_s:{{$}}
+; NO-SIMD128-NOT: i8x16
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i32{{$}}
+; SIMD128: i8x16.extract_lane_s $push0=, $0, 13{{$}}
+; SIMD128: return $pop0{{$}}
+define i32 @extract_v16i8_s(<16 x i8> %v) {
+  %elem = extractelement <16 x i8> %v, i8 13
+  %a = sext i8 %elem to i32
+  ret i32 %a
+}
+
+; CHECK-LABEL: extract_v16i8_u:{{$}}
+; NO-SIMD128-NOT: i8x16
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i32{{$}}
+; SIMD128: i8x16.extract_lane_u $push0=, $0, 13{{$}}
+; SIMD128: return $pop0{{$}}
+define i32 @extract_v16i8_u(<16 x i8> %v) {
+  %elem = extractelement <16 x i8> %v, i8 13
+  %a = zext i8 %elem to i32
+  ret i32 %a
+}
+
+; CHECK-LABEL: extract_v16i8:{{$}}
+; NO-SIMD128-NOT: i8x16
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i32{{$}}
+; SIMD128: i8x16.extract_lane_u $push0=, $0, 13{{$}}
+; SIMD128: return $pop0{{$}}
+define i8 @extract_v16i8(<16 x i8> %v) {
+  %elem = extractelement <16 x i8> %v, i8 13
+  ret i8 %elem
+}
+
+; ==============================================================================
+; 8 x i16
+; ==============================================================================
+; CHECK-LABEL: extract_v8i16_s:{{$}}
+; NO-SIMD128-NOT: i16x8
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i32{{$}}
+; SIMD128: i16x8.extract_lane_s $push0=, $0, 5{{$}}
+; SIMD128: return $pop0{{$}}
+define i32 @extract_v8i16_s(<8 x i16> %v) {
+  %elem = extractelement <8 x i16> %v, i16 5
+  %a = sext i16 %elem to i32
+  ret i32 %a
+}
+
+; CHECK-LABEL: extract_v8i16_u:{{$}}
+; NO-SIMD128-NOT: i16x8
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i32{{$}}
+; SIMD128: i16x8.extract_lane_u $push0=, $0, 5{{$}}
+; SIMD128: return $pop0{{$}}
+define i32 @extract_v8i16_u(<8 x i16> %v) {
+  %elem = extractelement <8 x i16> %v, i16 5
+  %a = zext i16 %elem to i32
+  ret i32 %a
+}
+
+; CHECK-LABEL: extract_v8i16:{{$}}
+; NO-SIMD128-NOT: i16x8
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i32{{$}}
+; SIMD128: i16x8.extract_lane_u $push0=, $0, 5{{$}}
+; SIMD128: return $pop0{{$}}
+define i16 @extract_v8i16(<8 x i16> %v) {
+  %elem = extractelement <8 x i16> %v, i16 5
+  ret i16 %elem
+}
+
+; ==============================================================================
+; 4 x i32
+; ==============================================================================
+; CHECK-LABEL: extract_v4i32:{{$}}
+; NO-SIMD128-NOT: i32x4
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i32{{$}}
+; SIMD128: i32x4.extract_lane $push0=, $0, 3{{$}}
+; SIMD128: return $pop0{{$}}
+define i32 @extract_v4i32(<4 x i32> %v) {
+  %elem = extractelement <4 x i32> %v, i32 3
+  ret i32 %elem
+}
+
+; ==============================================================================
+; 2 x i64
+; ==============================================================================
+; CHECK-LABEL: extract_v2i64:{{$}}
+; NO-SIMD128-NOT: i64x2
+; SIMD128-VM-NOT: i64x2
+; SIMD128: .param v128{{$}}
+; SIMD128: .result i64{{$}}
+; SIMD128: i64x2.extract_lane $push0=, $0, 1{{$}}
+; SIMD128: return $pop0{{$}}
+define i64 @extract_v2i64(<2 x i64> %v) {
+  %elem = extractelement <2 x i64> %v, i64 1
+  ret i64 %elem
+}
+
+; ==============================================================================
+; 4 x f32
+; ==============================================================================
+; CHECK-LABEL: extract_v4f32:{{$}}
+; NO-SIMD128-NOT: f32x4
+; SIMD128: .param v128{{$}}
+; SIMD128: .result f32{{$}}
+; SIMD128: f32x4.extract_lane $push0=, $0, 3{{$}}
+; SIMD128: return $pop0{{$}}
+define float @extract_v4f32(<4 x float> %v) {
+  %elem = extractelement <4 x float> %v, i32 3
+  ret float %elem
+}
+
+; ==============================================================================
+; 2 x f64
+; ==============================================================================
+; CHECK-LABEL: extract_v2f64:{{$}}
+; NO-SIMD128-NOT: f64x2
+; SIMD128-VM-NOT: f64x2
+; SIMD128: .param v128{{$}}
+; SIMD128: .result f64{{$}}
+; SIMD128: f64x2.extract_lane $push0=, $0, 1{{$}}
+; SIMD128: return $pop0{{$}}
+define double @extract_v2f64(<2 x double> %v) {
+  %elem = extractelement <2 x double> %v, i32 1
+  ret double %elem
+}