[shader_recompiler/Maxwell] Unstub ISBERD completely (#160)

Unstub previous ISBERD stubs.
Should improve internal shader handling in certain aspects.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/160
Co-authored-by: SDK Chan <sdkchan@eden-emu.dev>
Co-committed-by: SDK Chan <sdkchan@eden-emu.dev>

src/shader_recompiler/frontend/maxwell/translate/impl/internal_stage_buffer_entry_read.cpp

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -37,16 +40,56 @@ void TranslatorVisitor::ISBERD(u64 insn) {
     } const isberd{insn};
 
     if (isberd.skew != 0) {
-        throw NotImplementedException("SKEW");
+        IR::U32 current_lane_id{ir.LaneId()};
+        IR::U32 result{ir.IAdd(X(isberd.src_reg), current_lane_id)};
+        X(isberd.dest_reg, result);
     }
     if (isberd.o != 0) {
-        throw NotImplementedException("O");
+        IR::U32 address{};
+        IR::F32 result{};
+        if (isberd.src_reg_num == 0xFF) {
+            address = ir.Imm32(isberd.imm);
+            result = ir.GetAttributeIndexed(address);
+        } else {
+            IR::U32 offset = ir.Imm32(isberd.imm);
+            address = ir.IAdd(X(isberd.src_reg), offset);
+            result = ir.GetAttributeIndexed(address);
+        }
+        X(isberd.dest_reg, ir.BitCast<IR::U32>(result));
     }
     if (isberd.mode != Mode::Default) {
-        throw NotImplementedException("Mode {}", isberd.mode.Value());
+        IR::F32 result{};
+        IR::U32 index{};
+        if (isberd.src_reg_num == 0xFF) {
+            index = ir.Imm32(isberd.imm);
+        } else {
+            index = ir.IAdd(X(isberd.src_reg), ir.Imm32(isberd.imm));
+        }
+
+        switch (static_cast<u64>(isberd.mode.Value())) {
+        case static_cast<u64>(Mode::Patch):
+            result = ir.GetPatch(index.Patch());
+            break;
+        case static_cast<u64>(Mode::Prim):
+            result = ir.GetAttribute(index.Attribute());
+            break;
+        case static_cast<u64>(Mode::Attr):
+            result = ir.GetAttributeIndexed(index);
+            break;
+        }
+        X(isberd.dest_reg, ir.BitCast<IR::U32>(result));
     }
     if (isberd.shift != Shift::Default) {
-        throw NotImplementedException("Shift {}", isberd.shift.Value());
+        IR::U32 result{};
+        switch (static_cast<u64>(isberd.shift.Value())) {
+        case static_cast<u64>(Shift::U16):
+            result = ir.ShiftLeftLogical(result, static_cast<IR::U32>(ir.Imm16(1)));
+            break;
+        case static_cast<u64>(Shift::B32):
+            result = ir.ShiftLeftLogical(result, ir.Imm32(1));
+            break;
+        }
+        X(isberd.dest_reg, result);
     }
     //LOG_DEBUG(Shader, "(STUBBED) called {}", insn);
     if (isberd.src_reg_num == 0xFF) {