From b0e79208385ca3183fd1abdd4c6628268840e9ef Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Mon, 17 Dec 2018 18:09:40 -0300
Subject: shader_decode: Implement XMAD

---
 src/video_core/shader/decode/xmad.cpp | 86 ++++++++++++++++++++++++++++++++++-
 1 file changed, 85 insertions(+), 1 deletion(-)

(limited to 'src/video_core/shader')

diff --git a/src/video_core/shader/decode/xmad.cpp b/src/video_core/shader/decode/xmad.cpp
index 27a2fc05d..fcab1fb80 100644
--- a/src/video_core/shader/decode/xmad.cpp
+++ b/src/video_core/shader/decode/xmad.cpp
@@ -16,7 +16,91 @@ u32 ShaderIR::DecodeXmad(BasicBlock& bb, u32 pc) {
     const Instruction instr = {program_code[pc]};
     const auto opcode = OpCode::Decode(instr);
 
-    UNIMPLEMENTED();
+    UNIMPLEMENTED_IF(instr.xmad.sign_a);
+    UNIMPLEMENTED_IF(instr.xmad.sign_b);
+    UNIMPLEMENTED_IF_MSG(instr.generates_cc,
+                         "Condition codes generation in XMAD is not implemented");
+
+    Node op_a = GetRegister(instr.gpr8); // instr.xmad.sign_a
+
+    // TODO(bunnei): Needs to be fixed once op_a or op_b is signed
+    UNIMPLEMENTED_IF(instr.xmad.sign_a != instr.xmad.sign_b);
+    const bool is_signed_a = instr.xmad.sign_a == 1;
+    const bool is_signed_b = instr.xmad.sign_b == 1;
+    const bool is_signed_c = is_signed_a;
+
+    auto [is_merge, op_b, op_c] = [&]() -> std::tuple<bool, Node, Node> {
+        switch (opcode->get().GetId()) {
+        case OpCode::Id::XMAD_CR:
+            return {instr.xmad.merge_56, GetConstBuffer(instr.cbuf34.index, instr.cbuf34.offset),
+                    GetRegister(instr.gpr39)};
+        case OpCode::Id::XMAD_RR:
+            return {instr.xmad.merge_37, GetRegister(instr.gpr20), GetRegister(instr.gpr39)};
+        case OpCode::Id::XMAD_RC:
+            return {false, GetRegister(instr.gpr39),
+                    GetConstBuffer(instr.cbuf34.index, instr.cbuf34.offset)};
+        case OpCode::Id::XMAD_IMM:
+            return {instr.xmad.merge_37, Immediate(static_cast<u32>(instr.xmad.imm20_16)),
+                    GetRegister(instr.gpr39)};
+        default:
+            UNIMPLEMENTED_MSG("Unhandled XMAD instruction: {}", opcode->get().GetName());
+        }
+    }();
+
+    if (instr.xmad.high_a) {
+        op_a = SignedOperation(OperationCode::ILogicalShiftRight, is_signed_a, NO_PRECISE, op_a,
+                               Immediate(16));
+    } else {
+        op_a = SignedOperation(OperationCode::IBitwiseAnd, is_signed_a, NO_PRECISE, op_a,
+                               Immediate(0xffff));
+    }
+
+    const Node original_b = op_b;
+    if (instr.xmad.high_b) {
+        op_b = SignedOperation(OperationCode::ILogicalShiftRight, is_signed_b, NO_PRECISE, op_a,
+                               Immediate(16));
+    } else {
+        op_b = SignedOperation(OperationCode::IBitwiseAnd, is_signed_b, NO_PRECISE, op_b,
+                               Immediate(0xffff));
+    }
+
+    // TODO(Rodrigo): Use an appropiate sign for this operation
+    Node product = Operation(OperationCode::IMul, NO_PRECISE, op_a, op_b);
+    if (instr.xmad.product_shift_left) {
+        product = Operation(OperationCode::ILogicalShiftLeft, NO_PRECISE, op_a, Immediate(16));
+    }
+
+    op_c = [&]() {
+        switch (instr.xmad.mode) {
+        case Tegra::Shader::XmadMode::None:
+            return op_c;
+        case Tegra::Shader::XmadMode::CLo:
+            return SignedOperation(OperationCode::IBitwiseAnd, is_signed_c, NO_PRECISE, op_c,
+                                   Immediate(0xffff));
+        case Tegra::Shader::XmadMode::CHi:
+            return SignedOperation(OperationCode::ILogicalShiftRight, is_signed_c, NO_PRECISE, op_c,
+                                   Immediate(16));
+        case Tegra::Shader::XmadMode::CBcc: {
+            const Node shifted_b = SignedOperation(OperationCode::ILogicalShiftLeft, is_signed_b,
+                                                   NO_PRECISE, original_b, Immediate(16));
+            return SignedOperation(OperationCode::IAdd, is_signed_c, NO_PRECISE, op_c, shifted_b);
+        }
+        default: {
+            UNIMPLEMENTED_MSG("Unhandled XMAD mode: {}", static_cast<u32>(instr.xmad.mode.Value()));
+        }
+        }
+    }();
+
+    // TODO(Rodrigo): Use an appropiate sign for this operation
+    Node sum = Operation(OperationCode::IAdd, product, op_c);
+    if (is_merge) {
+        const Node a = Operation(OperationCode::IBitwiseAnd, NO_PRECISE, sum, Immediate(0xffff));
+        const Node b =
+            Operation(OperationCode::ILogicalShiftLeft, NO_PRECISE, original_b, Immediate(0xffff));
+        sum = Operation(OperationCode::IBitwiseOr, NO_PRECISE, a, b);
+    }
+
+    SetRegister(bb, instr.gpr0, sum);
 
     return pc;
 }
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