From d64848245d324a50835dc5cd96cb00513a8249b5 Mon Sep 17 00:00:00 2001
From: Joel Linn <jl@conductive.de>
Date: Wed, 16 Feb 2022 00:17:28 +0100
Subject: [PATCH] [CPU] Improve vrefp accuracy

---
 src/xenia/cpu/backend/x64/x64_emitter.cc   |  3 ++-
 src/xenia/cpu/backend/x64/x64_emitter.h    |  3 ++-
 src/xenia/cpu/backend/x64/x64_sequences.cc | 28 +++++++++++++++++-----
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/src/xenia/cpu/backend/x64/x64_emitter.cc b/src/xenia/cpu/backend/x64/x64_emitter.cc
index 5cd6780be..97b14e03e 100644
--- a/src/xenia/cpu/backend/x64/x64_emitter.cc
+++ b/src/xenia/cpu/backend/x64/x64_emitter.cc
@@ -2,7 +2,7 @@
  ******************************************************************************
  * Xenia : Xbox 360 Emulator Research Project                                 *
  ******************************************************************************
- * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Copyright 2022 Ben Vanik. All rights reserved.                             *
  * Released under the BSD license - see LICENSE in the root for more details. *
  ******************************************************************************
  */
@@ -653,6 +653,7 @@ void X64Emitter::MovMem64(const Xbyak::RegExp& addr, uint64_t v) {
 static const vec128_t xmm_consts[] = {
     /* XMMZero                */ vec128f(0.0f),
     /* XMMOne                 */ vec128f(1.0f),
+    /* XMMOnePD               */ vec128d(1.0),
     /* XMMNegativeOne         */ vec128f(-1.0f, -1.0f, -1.0f, -1.0f),
     /* XMMFFFF                */
     vec128i(0xFFFFFFFFu, 0xFFFFFFFFu, 0xFFFFFFFFu, 0xFFFFFFFFu),
diff --git a/src/xenia/cpu/backend/x64/x64_emitter.h b/src/xenia/cpu/backend/x64/x64_emitter.h
index 840e355fc..9117beea3 100644
--- a/src/xenia/cpu/backend/x64/x64_emitter.h
+++ b/src/xenia/cpu/backend/x64/x64_emitter.h
@@ -2,7 +2,7 @@
  ******************************************************************************
  * Xenia : Xbox 360 Emulator Research Project                                 *
  ******************************************************************************
- * Copyright 2019 Ben Vanik. All rights reserved.                             *
+ * Copyright 2022 Ben Vanik. All rights reserved.                             *
  * Released under the BSD license - see LICENSE in the root for more details. *
  ******************************************************************************
  */
@@ -49,6 +49,7 @@ enum RegisterFlags {
 enum XmmConst {
   XMMZero = 0,
   XMMOne,
+  XMMOnePD,
   XMMNegativeOne,
   XMMFFFF,
   XMMMaskX16Y16,
diff --git a/src/xenia/cpu/backend/x64/x64_sequences.cc b/src/xenia/cpu/backend/x64/x64_sequences.cc
index 62f6e9a3f..08badaa9c 100644
--- a/src/xenia/cpu/backend/x64/x64_sequences.cc
+++ b/src/xenia/cpu/backend/x64/x64_sequences.cc
@@ -2,7 +2,7 @@
  ******************************************************************************
  * Xenia : Xbox 360 Emulator Research Project                                 *
  ******************************************************************************
- * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Copyright 2022 Ben Vanik. All rights reserved.                             *
  * Released under the BSD license - see LICENSE in the root for more details. *
  ******************************************************************************
  */
@@ -2376,21 +2376,37 @@ EMITTER_OPCODE_TABLE(OPCODE_RSQRT, RSQRT_F32, RSQRT_F64, RSQRT_V128);
 // ============================================================================
 // OPCODE_RECIP
 // ============================================================================
+// Altivec guarantees an error of < 1/4096 for vrefp while AVX only gives
+// < 1.5*2^-12 ≈ 1/2730 for rcpps. This breaks camp, horse and random event
+// spawning, breaks cactus collision as well as flickering grass in 5454082B
 struct RECIP_F32 : Sequence<RECIP_F32, I<OPCODE_RECIP, F32Op, F32Op>> {
   static void Emit(X64Emitter& e, const EmitArgType& i) {
-    e.vrcpss(i.dest, i.src1);
+    if (e.IsFeatureEnabled(kX64EmitAVX512Ortho)) {
+      e.vrcp14ss(i.dest, i.src1, i.src1);
+    } else {
+      e.vmovaps(e.xmm0, e.GetXmmConstPtr(XMMOne));
+      e.vdivss(i.dest, e.xmm0, i.src1);
+    }
   }
 };
 struct RECIP_F64 : Sequence<RECIP_F64, I<OPCODE_RECIP, F64Op, F64Op>> {
   static void Emit(X64Emitter& e, const EmitArgType& i) {
-    e.vcvtsd2ss(i.dest, i.src1);
-    e.vrcpss(i.dest, i.dest);
-    e.vcvtss2sd(i.dest, i.dest);
+    if (e.IsFeatureEnabled(kX64EmitAVX512Ortho)) {
+      e.vrcp14sd(i.dest, i.src1, i.src1);
+    } else {
+      e.vmovapd(e.xmm0, e.GetXmmConstPtr(XMMOnePD));
+      e.vdivsd(i.dest, e.xmm0, i.src1);
+    }
   }
 };
 struct RECIP_V128 : Sequence<RECIP_V128, I<OPCODE_RECIP, V128Op, V128Op>> {
   static void Emit(X64Emitter& e, const EmitArgType& i) {
-    e.vrcpps(i.dest, i.src1);
+    if (e.IsFeatureEnabled(kX64EmitAVX512Ortho)) {
+      e.vrcp14ps(i.dest, i.src1);
+    } else {
+      e.vmovaps(e.xmm0, e.GetXmmConstPtr(XMMOne));
+      e.vdivps(i.dest, e.xmm0, i.src1);
+    }
   }
 };
 EMITTER_OPCODE_TABLE(OPCODE_RECIP, RECIP_F32, RECIP_F64, RECIP_V128);