shader: emit constant-true guarded blocks inline and fold immediate constant-buffer indices

src/graphics/shader/recompiler/backend/spirv/spirvEmitterInternal.h

@@ -580,6 +580,10 @@ auto EmitIndexSwitch(EmitterState& state, uint32_t index, uint32_t count,
 
 template <typename Fn>
 void EmitIfCondition(EmitterState& state, uint32_t condition, Fn&& fn) {
+	if (condition == ConstantBool(state, true)) {
+		fn();
+		return;
+	}
 	const auto then_label  = state.builder.AllocateId();
 	const auto merge_label = state.builder.AllocateId();
 	state.builder.AddFunction(spv::OpSelectionMerge, merge_label, spv::SelectionControlMaskNone);
@@ -593,6 +597,7 @@ void EmitIfCondition(EmitterState& state, uint32_t condition, Fn&& fn) {
 template <typename Fn>
 uint32_t EmitValueOrDefaultIfCondition(EmitterState& state, uint32_t condition, uint32_t type,
                                        uint32_t default_value, Fn&& fn) {
+	if (condition == ConstantBool(state, true)) return fn();
 	const auto then_label  = state.builder.AllocateId();
 	const auto header     = state.current_label;
 	const auto merge_label = state.builder.AllocateId();

src/graphics/shader/recompiler/backend/spirv/spirvEmitterMemory.cpp

@@ -1605,9 +1605,12 @@ void EmitReadConstBuffer(ValueEmitContext& ctx, const IR::Inst& inst) {
 	}
 	auto& state        = ctx.state;
 	mem.kind           = IR::ResourceKind::ScalarBuffer;
-	auto index = Binary(state, spv::OpShiftRightLogical, TypeU32(state), ctx.Arg(inst, 1),
+	const auto offset = inst.Arg(1).Resolve();
-	                    ConstantU32(state, 2));
+	auto       index  = offset.IsImmediate()
-	if (mem.offset >= 4u) {
+	                        ? ConstantU32(state, (offset.U32() >> 2u) + (mem.offset >> 2u))
+	                        : Binary(state, spv::OpShiftRightLogical, TypeU32(state),
+	                                 ctx.Arg(inst, 1), ConstantU32(state, 2));
+	if (!offset.IsImmediate() && mem.offset >= 4u) {
 		index = Binary(state, spv::OpIAdd, TypeU32(state), index, ConstantU32(state, mem.offset >> 2u));
 	}
 	const auto access    = PrepareMemoryResourceAccess(state, mem);

tests/shaderCfgTests.cpp

@@ -10532,6 +10532,7 @@ void TestComputeDispatchWaveSize() {
 
 void TestNewShaderRecompilerBufferLoadsGuardedByExec() {
   const uint32_t shader[] = {
+      EncodeVopc(0xd4, 0 + 256, 1), // v_cmpx_gt_u32 v0, v1
       EncodeMubuf0(0x0c),
       EncodeMubuf1(0, 0, 1), // buffer_load_dword
                              // v0