Merge pull request #639 from KhronosGroup/fix-638

Properly track read dependencies for UAV access chain.

reference/opt/shaders-hlsl/asm/comp/access-chain-invalidate.asm.comp

@@ -0,0 +1,19 @@
+RWByteAddressBuffer _4 : register(u0);
+
+void comp_main()
+{
+    uint _21 = _4.Load(_4.Load(0) * 4 + 4);
+    for (uint _23 = 0u; _23 < 64u; )
+    {
+        _4.Store(_23 * 4 + 4, 0u);
+        _23++;
+        continue;
+    }
+    _4.Store(_4.Load(0) * 4 + 4, _21);
+}
+
+[numthreads(1, 1, 1)]
+void main()
+{
+    comp_main();
+}

reference/shaders-hlsl/asm/comp/access-chain-invalidate.asm.comp

@@ -0,0 +1,19 @@
+RWByteAddressBuffer _4 : register(u0);
+
+void comp_main()
+{
+    uint _21 = _4.Load(_4.Load(0) * 4 + 4);
+    for (uint _23 = 0u; _23 < 64u; )
+    {
+        _4.Store(_23 * 4 + 4, 0u);
+        _23++;
+        continue;
+    }
+    _4.Store(_4.Load(0) * 4 + 4, _21);
+}
+
+[numthreads(1, 1, 1)]
+void main()
+{
+    comp_main();
+}

shaders-hlsl/asm/comp/access-chain-invalidate.asm.comp

@@ -0,0 +1,61 @@
+; SPIR-V
+; Version: 1.0
+; Generator: Google Shaderc over Glslang; 7
+; Bound: 41
+; Schema: 0
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %main "main"
+               OpExecutionMode %main LocalSize 1 1 1
+               OpSource GLSL 450
+               OpSourceExtension "GL_GOOGLE_cpp_style_line_directive"
+               OpSourceExtension "GL_GOOGLE_include_directive"
+               OpName %main "main"
+               OpName %SSBO "SSBO"
+               OpMemberName %SSBO 0 "index"
+               OpMemberName %SSBO 1 "array"
+               OpName %_ ""
+               OpDecorate %_arr_uint_uint_64 ArrayStride 4
+               OpMemberDecorate %SSBO 0 Offset 0
+               OpMemberDecorate %SSBO 1 Offset 4
+               OpDecorate %SSBO BufferBlock
+               OpDecorate %_ DescriptorSet 0
+               OpDecorate %_ Binding 0
+       %void = OpTypeVoid
+          %3 = OpTypeFunction %void
+       %uint = OpTypeInt 32 0
+    %uint_64 = OpConstant %uint 64
+%_arr_uint_uint_64 = OpTypeArray %uint %uint_64
+       %SSBO = OpTypeStruct %uint %_arr_uint_uint_64
+%_ptr_Uniform_SSBO = OpTypePointer Uniform %SSBO
+          %_ = OpVariable %_ptr_Uniform_SSBO Uniform
+        %int = OpTypeInt 32 1
+      %int_1 = OpConstant %int 1
+      %int_0 = OpConstant %int 0
+%_ptr_Uniform_uint = OpTypePointer Uniform %uint
+     %uint_0 = OpConstant %uint 0
+       %bool = OpTypeBool
+       %main = OpFunction %void None %3
+          %5 = OpLabel
+         %18 = OpAccessChain %_ptr_Uniform_uint %_ %int_0
+         %19 = OpLoad %uint %18
+         %20 = OpAccessChain %_ptr_Uniform_uint %_ %int_1 %19
+         %21 = OpLoad %uint %20
+               OpBranch %24
+         %24 = OpLabel
+         %40 = OpPhi %uint %uint_0 %5 %35 %25
+         %31 = OpULessThan %bool %40 %uint_64
+               OpLoopMerge %26 %25 None
+               OpBranchConditional %31 %25 %26
+         %25 = OpLabel
+         %33 = OpAccessChain %_ptr_Uniform_uint %_ %int_1 %40
+               OpStore %33 %uint_0
+         %35 = OpIAdd %uint %40 %int_1
+               OpBranch %24
+         %26 = OpLabel
+         %37 = OpLoad %uint %18
+         %39 = OpAccessChain %_ptr_Uniform_uint %_ %int_1 %37
+               OpStore %39 %21
+               OpReturn
+               OpFunctionEnd

spirv_glsl.cpp

@@ -6147,7 +6147,7 @@ void CompilerGLSL::emit_instruction(const Instruction &instruction)
 		if (ptr_expression)
 			ptr_expression->need_transpose = old_need_transpose;
 
-		// By default, suppress usage tracking since using same expressio multiple times does not imply any extra work.
+		// By default, suppress usage tracking since using same expression multiple times does not imply any extra work.
 		// However, if we try to load a complex, composite object from a flattened buffer,
 		// we should avoid emitting the same code over and over and lower the result to a temporary.
 		auto &type = get<SPIRType>(result_type);

spirv_hlsl.cpp

@@ -3519,6 +3519,7 @@ void CompilerHLSL::emit_access_chain(const Instruction &instruction)
 	if (need_byte_access_chain)
 	{
 		uint32_t to_plain_buffer_length = static_cast<uint32_t>(type.array.size());
+		auto *backing_variable = maybe_get_backing_variable(ops[2]);
 
 		string base;
 		if (to_plain_buffer_length != 0)
@@ -3557,6 +3558,7 @@ void CompilerHLSL::emit_access_chain(const Instruction &instruction)
 		e.row_major_matrix = row_major_matrix;
 		e.matrix_stride = matrix_stride;
 		e.immutable = should_forward(ops[2]);
+		e.loaded_from = backing_variable ? backing_variable->self : 0;
 
 		if (chain)
 		{