From 108e98ec32ba61a19965611206633cd2ebb0d6ba Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Wed, 10 Oct 2018 01:09:09 +0000
Subject: [PATCH] [WebAssembly] Fix fneg lowering

Summary:
Subtraction from zero and floating point negation do not have the same
semantics, so fix lowering.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D52948

llvm-svn: 344107
---
 .../lib/Target/WebAssembly/WebAssemblyInstrSIMD.td | 41 +++++++---------------
 llvm/test/CodeGen/WebAssembly/simd-arith.ll        |  6 ++--
 2 files changed, 17 insertions(+), 30 deletions(-)

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
index 672f391..28262fb 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -400,6 +400,9 @@ multiclass SIMDBinaryInt<SDNode node, string name, bits<32> baseInst> {
   defm "" : SIMDBinary<v2i64, "i64x2", node, name, !add(baseInst, 3)>;
 }
 
+// Integer vector negation
+def ivneg : PatFrag<(ops node:$in), (sub immAllZerosV, node:$in)>;
+
 // Integer addition: add
 let isCommutable = 1 in
 defm ADD : SIMDBinaryInt<add, "add", 24>;
@@ -411,29 +414,18 @@ defm SUB : SIMDBinaryInt<sub, "sub", 28>;
 defm MUL : SIMDBinaryIntNoI64x2<mul, "mul", 32>;
 
 // Integer negation: neg
-multiclass SIMDNeg<ValueType vec_t, string vec, PatFrag splat_pat,
-                   ValueType lane_t, SDNode node, dag lane, bits<32> simdop> {
-  defm NEG_#vec_t : SIMD_I<(outs V128:$dst), (ins V128:$vec),
-                           (outs), (ins),
-                           [(set
-                             (vec_t V128:$dst),
-                             (vec_t (node
-                               (vec_t (splat_pat lane)),
-                               (vec_t V128:$vec)
-                             ))
+multiclass SIMDNeg<ValueType vec_t, string vec, SDNode neg, bits<32> simdop> {
+  defm NEG_#vec_t : SIMD_I<(outs V128:$dst), (ins V128:$vec), (outs), (ins),
+                           [(set (vec_t V128:$dst),
+                             (vec_t (neg (vec_t V128:$vec)))
                            )],
                            vec#".neg\t$dst, $vec", vec#".neg", simdop>;
 }
 
-multiclass SIMDNegInt<ValueType vec_t, string vec, PatFrag splat_pat,
-                      ValueType lane_t, bits<32> simdop> {
-  defm "" : SIMDNeg<vec_t, vec, splat_pat, lane_t, sub, (lane_t 0), simdop>;
-}
-
-defm "" : SIMDNegInt<v16i8, "i8x16", splat16, i32, 36>;
-defm "" : SIMDNegInt<v8i16, "i16x8", splat8, i32, 37>;
-defm "" : SIMDNegInt<v4i32, "i32x4", splat4, i32, 38>;
-defm "" : SIMDNegInt<v2i64, "i64x2", splat2, i64, 39>;
+defm "" : SIMDNeg<v16i8, "i8x16", ivneg, 36>;
+defm "" : SIMDNeg<v8i16, "i16x8", ivneg, 37>;
+defm "" : SIMDNeg<v4i32, "i32x4", ivneg, 38>;
+defm "" : SIMDNeg<v2i64, "i64x2", ivneg, 39>;
 
 //===----------------------------------------------------------------------===//
 // Saturating integer arithmetic
@@ -718,15 +710,8 @@ def : StorePatExternSymOffOnly<vec_t, store, !cast<NI>("STORE_"#vec_t)>;
 //===----------------------------------------------------------------------===//
 
 // Negation: neg
-def fpimm0 : FPImmLeaf<fAny, [{ return Imm.isExactlyValue(+0.0); }]>;
-multiclass SIMDNegFP<ValueType vec_t, string vec, PatFrag splat_pat,
-                     ValueType lane_t, bits<32> simdop> {
-  defm "" : SIMDNeg<vec_t, vec, splat_pat, lane_t, fsub, (lane_t fpimm0),
-                    simdop>;
-}
-
-defm "" : SIMDNegFP<v4f32, "f32x4", splat4, f32, 125>;
-defm "" : SIMDNegFP<v2f64, "f64x2", splat2, f64, 126>;
+defm "" : SIMDNeg<v4f32, "f32x4", fneg, 125>;
+defm "" : SIMDNeg<v2f64, "f64x2", fneg, 126>;
 
 // Absolute value: abs
 multiclass SIMDAbs<ValueType vec_t, string vec, bits<32> simdop> {
diff --git a/llvm/test/CodeGen/WebAssembly/simd-arith.ll b/llvm/test/CodeGen/WebAssembly/simd-arith.ll
index 0bda334..f3e7015 100644
--- a/llvm/test/CodeGen/WebAssembly/simd-arith.ll
+++ b/llvm/test/CodeGen/WebAssembly/simd-arith.ll
@@ -748,7 +748,8 @@ define <2 x i64> @bitselect_v2i64(<2 x i64> %c, <2 x i64> %v1, <2 x i64> %v2) {
 ; SIMD128-NEXT: f32x4.neg $push[[R:[0-9]+]]=, $0{{$}}
 ; SIMD128-NEXT: return $pop[[R]]{{$}}
 define <4 x float> @neg_v4f32(<4 x float> %x) {
-  %a = fsub <4 x float> <float 0., float 0., float 0., float 0.>, %x
+  ; nsz makes this semantically equivalent to flipping sign bit
+  %a = fsub nsz <4 x float> <float 0.0, float 0.0, float 0.0, float 0.0>, %x
   ret <4 x float> %a
 }
 
@@ -830,7 +831,8 @@ define <4 x float> @sqrt_v4f32(<4 x float> %x) {
 ; SIMD128-NEXT: f64x2.neg $push[[R:[0-9]+]]=, $0{{$}}
 ; SIMD128-NEXT: return $pop[[R]]{{$}}
 define <2 x double> @neg_v2f64(<2 x double> %x) {
-  %a = fsub <2 x double> <double 0., double 0.>, %x
+  ; nsz makes this semantically equivalent to flipping sign bit
+  %a = fsub nsz <2 x double> <double 0., double 0.>, %x
   ret <2 x double> %a
 }
 
-- 
2.7.4