From 2f88a0a3b293fbe010d13e941b968304b498c157 Mon Sep 17 00:00:00 2001
From: nmzik <Nmzik@mail.ru>
Date: Tue, 13 Oct 2026 00:53:23 +0200
Subject: [PATCH] shader: elide bitcasts between identical physical types

---
 .../backend/spirv/spirvEmitterInstructions.h  |  7 +++---
 tests/ShaderRecompilerComputeTests.cpp        | 22 ++++++++++++++++---
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/graphics/shader/recompiler/backend/spirv/spirvEmitterInstructions.h b/src/graphics/shader/recompiler/backend/spirv/spirvEmitterInstructions.h
index 6bd749e6..ad6b3138 100644
--- a/src/graphics/shader/recompiler/backend/spirv/spirvEmitterInstructions.h
+++ b/src/graphics/shader/recompiler/backend/spirv/spirvEmitterInstructions.h
@@ -5,15 +5,17 @@
 #include <bit>
 
 namespace Libs::Graphics::ShaderRecompiler::Spirv::Emitter {
+uint32_t EmitIdentity(ValueEmitContext& ctx, uint32_t value);
+
 // Operand signatures distinguish SPIR-V IDs (uint32_t), raw literals/values
 // (IR::Value), and instructions whose metadata or operand loads must stay lazy.
 #define EMIT_NATIVE(name, opcode, type, ...)                                                       \
 	inline constexpr auto Emit##name = EmitNative<spv::opcode, IR::Type::type, __VA_ARGS__>;
-EMIT_NATIVE(BitCastU16F16, OpBitcast, U32, uint32_t)
+inline constexpr auto EmitBitCastU16F16 = EmitIdentity;
 inline constexpr auto EmitBitCastF16U16 = EmitBitCastU16F16;
 inline constexpr auto EmitConvertU32U16 = EmitBitCastU16F16;
 inline constexpr auto EmitConvertU32U8  = EmitBitCastU16F16;
-inline constexpr auto EmitBitCastU32F32 = EmitBitCastU16F16;
+EMIT_NATIVE(BitCastU32F32, OpBitcast, U32, uint32_t)
 EMIT_NATIVE(BitCastF32U32, OpBitcast, F32, uint32_t)
 EMIT_NATIVE(BitCastU64F64, OpBitcast, U64, uint32_t)
 EMIT_NATIVE(BitCastF64U64, OpBitcast, F64, uint32_t)
@@ -207,7 +209,6 @@ uint32_t              EmitFPSin(EmitterState& state, uint32_t arg0);
 uint32_t              EmitFPCos(EmitterState& state, uint32_t arg0);
 #undef EMIT_NATIVE
 
-uint32_t              EmitIdentity(ValueEmitContext& ctx, uint32_t value);
 void                  EmitVoid(ValueEmitContext&);
 inline constexpr auto EmitReference    = EmitVoid;
 inline constexpr auto EmitReferenceU32 = EmitVoid;
diff --git a/tests/ShaderRecompilerComputeTests.cpp b/tests/ShaderRecompilerComputeTests.cpp
index ac3b7e2e..064aaf0f 100644
--- a/tests/ShaderRecompilerComputeTests.cpp
+++ b/tests/ShaderRecompilerComputeTests.cpp
@@ -1,3 +1,5 @@
+#define SPV_ENABLE_UTILITY_CODE
+
 #include "common/assert.h"
 #include "common/emulatorConfig.h"
 #include "common/file.h"
@@ -1610,7 +1612,21 @@ void CheckRectListShaders() {
   ValidateSpirv(name, position_only.evaluation);
 }
 
-void CheckSpirvText(const TestCase &test, const std::vector<u32> &spirv) {
+void CheckSpirvEmission(const TestCase &test, const std::vector<u32> &spirv) {
+  std::vector<u32> result_types(spirv[3]);
+  for (size_t offset = 5; offset < spirv.size();) {
+    const auto words = std::span<const u32>(spirv).subspan(offset, spirv[offset] >> 16u);
+    const auto opcode = static_cast<spv::Op>(words[0] & 0xffffu);
+    bool has_result = false, has_type = false;
+    spv::HasResultAndType(opcode, &has_result, &has_type);
+    if (has_result && has_type) result_types[words[2]] = words[1];
+    if (opcode == spv::OpBitcast) {
+      Require(test.name, "bitcast changes representation",
+              words[1] != result_types[words[3]],
+              "emitted a redundant bitcast between identical SPIR-V types");
+    }
+    offset += words.size();
+  }
   if (test.required_spirv.empty() && test.forbidden_spirv.empty()) {
     return;
   }
@@ -1737,7 +1753,7 @@ CompiledShader CompileCase(const TestCase &test, u32 host_subgroup_size = 64) {
   Require(test.name, "SPIR-V emit", !result.spirv.empty(),
           "recompiler returned empty SPIR-V");
   ValidateSpirv(test.name, result.spirv);
-  CheckSpirvText(test, result.spirv);
+  CheckSpirvEmission(test, result.spirv);
   if (test.expected_buffer_resources) {
     std::vector<u32> resources;
     for (u32 i = 0; i < result.program.info.buffers.size(); ++i) {
@@ -36184,7 +36200,7 @@ void CheckIndirectBufferStore(VulkanHarness &vulkan) {
     } else {
       test.required_spirv = {"OpSwitch"};
     }
-    CheckSpirvText(test, compiled.spirv);
+    CheckSpirvEmission(test, compiled.spirv);
 
     for (const bool swapped : {false, true}) {
       if (layout != Layout::Shared && layout != Layout::IndexedNullChild && swapped) continue;