From 34ac9b4d7e71198503d7fca88c0494e1f97701e7 Mon Sep 17 00:00:00 2001
From: ameerj <52414509+ameerj@users.noreply.github.com>
Date: Sat, 27 Feb 2021 01:45:13 -0500
Subject: shader: Implement BFE

---
 src/shader_recompiler/CMakeLists.txt               |  1 +
 .../maxwell/translate/impl/bitfield_extract.cpp    | 66 ++++++++++++++++++++++
 .../maxwell/translate/impl/not_implemented.cpp     | 12 ----
 3 files changed, 67 insertions(+), 12 deletions(-)
 create mode 100644 src/shader_recompiler/frontend/maxwell/translate/impl/bitfield_extract.cpp

diff --git a/src/shader_recompiler/CMakeLists.txt b/src/shader_recompiler/CMakeLists.txt
index b4d2dcc42..8be2d353f 100644
--- a/src/shader_recompiler/CMakeLists.txt
+++ b/src/shader_recompiler/CMakeLists.txt
@@ -59,6 +59,7 @@ add_library(shader_recompiler STATIC
     frontend/maxwell/opcodes.h
     frontend/maxwell/program.cpp
     frontend/maxwell/program.h
+    frontend/maxwell/translate/impl/bitfield_extract.cpp
     frontend/maxwell/translate/impl/common_encoding.h
     frontend/maxwell/translate/impl/floating_point_add.cpp
     frontend/maxwell/translate/impl/floating_point_conversion_integer.cpp
diff --git a/src/shader_recompiler/frontend/maxwell/translate/impl/bitfield_extract.cpp b/src/shader_recompiler/frontend/maxwell/translate/impl/bitfield_extract.cpp
new file mode 100644
index 000000000..4a03e6939
--- /dev/null
+++ b/src/shader_recompiler/frontend/maxwell/translate/impl/bitfield_extract.cpp
@@ -0,0 +1,66 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/bit_field.h"
+#include "common/common_types.h"
+#include "shader_recompiler/frontend/maxwell/translate/impl/impl.h"
+
+namespace Shader::Maxwell {
+namespace {
+void BFE(TranslatorVisitor& v, u64 insn, const IR::U32& src) {
+    union {
+        u64 insn;
+        BitField<0, 8, IR::Reg> dest_reg;
+        BitField<8, 8, IR::Reg> offset_reg;
+        BitField<40, 1, u64> brev;
+        BitField<48, 1, u64> is_signed;
+    } const bfe{insn};
+
+    const IR::U32 offset{v.ir.BitFieldExtract(src, v.ir.Imm32(0), v.ir.Imm32(8), false)};
+    const IR::U32 count{v.ir.BitFieldExtract(src, v.ir.Imm32(8), v.ir.Imm32(8), false)};
+
+    // Common constants
+    const IR::U32 zero{v.ir.Imm32(0)};
+    const IR::U32 one{v.ir.Imm32(1)};
+    const IR::U32 max_size{v.ir.Imm32(32)};
+    // Edge case conditions
+    const IR::U1 zero_count{v.ir.IEqual(count, zero)};
+    const IR::U1 exceed_count{v.ir.IGreaterThanEqual(v.ir.IAdd(offset, count), max_size, false)};
+    const IR::U1 replicate{v.ir.IGreaterThanEqual(offset, max_size, false)};
+
+    IR::U32 base{v.X(bfe.offset_reg)};
+    if (bfe.brev != 0) {
+        base = v.ir.BitReverse(base);
+    }
+    IR::U32 result{v.ir.BitFieldExtract(base, offset, count, bfe.is_signed != 0)};
+    if (bfe.is_signed != 0) {
+        const IR::U1 is_negative{v.ir.ILessThan(base, zero, true)};
+        const IR::U32 replicated_bit{v.ir.Select(is_negative, v.ir.Imm32(-1), zero)};
+        const IR::U32 exceed_bit{v.ir.BitFieldExtract(base, v.ir.Imm32(31), one, false)};
+        // Replicate condition
+        result = IR::U32{v.ir.Select(replicate, replicated_bit, result)};
+        // Exceeding condition
+        const IR::U32 exceed_result{v.ir.BitFieldInsert(result, exceed_bit, v.ir.Imm32(31), one)};
+        result = IR::U32{v.ir.Select(exceed_count, exceed_result, result)};
+    }
+    // Zero count condition
+    result = IR::U32{v.ir.Select(zero_count, zero, result)};
+
+    v.X(bfe.dest_reg, result);
+}
+} // Anonymous namespace
+
+void TranslatorVisitor::BFE_reg(u64 insn) {
+    BFE(*this, insn, GetReg20(insn));
+}
+
+void TranslatorVisitor::BFE_cbuf(u64 insn) {
+    BFE(*this, insn, GetCbuf(insn));
+}
+
+void TranslatorVisitor::BFE_imm(u64 insn) {
+    BFE(*this, insn, GetImm20(insn));
+}
+
+} // namespace Shader::Maxwell
diff --git a/src/shader_recompiler/frontend/maxwell/translate/impl/not_implemented.cpp b/src/shader_recompiler/frontend/maxwell/translate/impl/not_implemented.cpp
index 127686b43..3714f5f4f 100644
--- a/src/shader_recompiler/frontend/maxwell/translate/impl/not_implemented.cpp
+++ b/src/shader_recompiler/frontend/maxwell/translate/impl/not_implemented.cpp
@@ -49,18 +49,6 @@ void TranslatorVisitor::BAR(u64) {
     ThrowNotImplemented(Opcode::BAR);
 }
 
-void TranslatorVisitor::BFE_reg(u64) {
-    ThrowNotImplemented(Opcode::BFE_reg);
-}
-
-void TranslatorVisitor::BFE_cbuf(u64) {
-    ThrowNotImplemented(Opcode::BFE_cbuf);
-}
-
-void TranslatorVisitor::BFE_imm(u64) {
-    ThrowNotImplemented(Opcode::BFE_imm);
-}
-
 void TranslatorVisitor::BFI_reg(u64) {
     ThrowNotImplemented(Opcode::BFI_reg);
 }
-- 
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