Handle value access in terminators.

Fixes case where value is created inside loop body and consumed by a
return outside it.

reference/shaders-no-opt/asm/comp/temorary-access-terminator.vk.nocompat.asm.comp.vk

@@ -0,0 +1,36 @@
+#version 450
+#extension GL_KHR_shader_subgroup_ballot : require
+layout(local_size_x = 64, local_size_y = 1, local_size_z = 1) in;
+
+layout(set = 0, binding = 0) uniform usamplerBuffer _4;
+layout(set = 0, binding = 0, r32ui) uniform writeonly uimageBuffer _5;
+
+uvec4 WaveMatch(uint _45)
+{
+    uvec4 _52;
+    for (;;)
+    {
+        bool _51 = _45 == subgroupBroadcastFirst(_45);
+        _52 = subgroupBallot(_51);
+        if (_51)
+        {
+            break;
+        }
+        else
+        {
+            continue;
+        }
+    }
+    return _52;
+}
+
+void main()
+{
+    uvec4 _32 = WaveMatch(texelFetch(_4, int(gl_GlobalInvocationID.x)).x);
+    uint _37 = gl_GlobalInvocationID.x * 4u;
+    imageStore(_5, int(_37), uvec4(_32.x));
+    imageStore(_5, int(_37 + 1u), uvec4(_32.y));
+    imageStore(_5, int(_37 + 2u), uvec4(_32.z));
+    imageStore(_5, int(_37 + 3u), uvec4(_32.w));
+}
+

shaders-no-opt/asm/comp/temorary-access-terminator.vk.nocompat.asm.comp

@@ -0,0 +1,86 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Unknown(30017); 21022
+; Bound: 55
+; Schema: 0
+               OpCapability Shader
+               OpCapability SampledBuffer
+               OpCapability ImageBuffer
+               OpCapability GroupNonUniform
+               OpCapability GroupNonUniformBallot
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %main "main" %gl_GlobalInvocationID
+               OpExecutionMode %main LocalSize 64 1 1
+               OpName %main "main"
+               OpName %WaveMatch "WaveMatch"
+               OpDecorate %8 DescriptorSet 0
+               OpDecorate %8 Binding 0
+               OpDecorate %11 DescriptorSet 0
+               OpDecorate %11 Binding 0
+               OpDecorate %11 NonReadable
+               OpDecorate %gl_GlobalInvocationID BuiltIn GlobalInvocationId
+       %void = OpTypeVoid
+          %2 = OpTypeFunction %void
+       %uint = OpTypeInt 32 0
+          %6 = OpTypeImage %uint Buffer 0 0 0 1 Unknown
+%_ptr_UniformConstant_6 = OpTypePointer UniformConstant %6
+          %8 = OpVariable %_ptr_UniformConstant_6 UniformConstant
+          %9 = OpTypeImage %uint Buffer 0 0 0 2 R32ui
+%_ptr_UniformConstant_9 = OpTypePointer UniformConstant %9
+         %11 = OpVariable %_ptr_UniformConstant_9 UniformConstant
+     %v3uint = OpTypeVector %uint 3
+%_ptr_Input_v3uint = OpTypePointer Input %v3uint
+%gl_GlobalInvocationID = OpVariable %_ptr_Input_v3uint Input
+%_ptr_Input_uint = OpTypePointer Input %uint
+     %uint_0 = OpConstant %uint 0
+     %v4uint = OpTypeVector %uint 4
+         %24 = OpTypeFunction %v4uint %uint
+     %uint_3 = OpConstant %uint 3
+       %bool = OpTypeBool
+     %uint_4 = OpConstant %uint 4
+     %uint_1 = OpConstant %uint 1
+     %uint_2 = OpConstant %uint 2
+       %main = OpFunction %void None %2
+          %4 = OpLabel
+               OpBranch %53
+         %53 = OpLabel
+         %12 = OpLoad %9 %11
+         %13 = OpLoad %6 %8
+         %18 = OpAccessChain %_ptr_Input_uint %gl_GlobalInvocationID %uint_0
+         %20 = OpLoad %uint %18
+         %22 = OpImageFetch %v4uint %13 %20
+         %23 = OpCompositeExtract %uint %22 0
+         %37 = OpFunctionCall %v4uint %WaveMatch %23
+         %38 = OpCompositeExtract %uint %37 0
+         %39 = OpCompositeExtract %uint %37 1
+         %40 = OpCompositeExtract %uint %37 2
+         %41 = OpCompositeExtract %uint %37 3
+         %42 = OpIMul %uint %20 %uint_4
+         %44 = OpCompositeConstruct %v4uint %38 %38 %38 %38
+               OpImageWrite %12 %42 %44
+         %45 = OpCompositeConstruct %v4uint %39 %39 %39 %39
+         %46 = OpIAdd %uint %42 %uint_1
+               OpImageWrite %12 %46 %45
+         %48 = OpCompositeConstruct %v4uint %40 %40 %40 %40
+         %49 = OpIAdd %uint %42 %uint_2
+               OpImageWrite %12 %49 %48
+         %51 = OpCompositeConstruct %v4uint %41 %41 %41 %41
+         %52 = OpIAdd %uint %42 %uint_3
+               OpImageWrite %12 %52 %51
+               OpReturn
+               OpFunctionEnd
+  %WaveMatch = OpFunction %v4uint None %24
+         %25 = OpFunctionParameter %uint
+         %27 = OpLabel
+               OpBranch %28
+         %28 = OpLabel
+               OpLoopMerge %30 %29 None
+               OpBranch %29
+         %29 = OpLabel
+         %31 = OpGroupNonUniformBroadcastFirst %uint %uint_3 %25
+         %34 = OpIEqual %bool %25 %31
+         %35 = OpGroupNonUniformBallot %v4uint %uint_3 %34
+               OpBranchConditional %34 %30 %28
+         %30 = OpLabel
+               OpReturnValue %35
+               OpFunctionEnd

spirv_cross.cpp

@@ -1659,6 +1659,9 @@ bool Compiler::traverse_all_reachable_opcodes(const SPIRBlock &block, OpcodeHand
 		}
 	}
 
+	if (!handler.handle_terminator(block))
+		return false;
+
 	return true;
 }
 
@@ -3055,6 +3058,27 @@ bool Compiler::AnalyzeVariableScopeAccessHandler::id_is_potential_temporary(uint
 	return compiler.ir.ids[id].empty() || (compiler.ir.ids[id].get_type() == TypeExpression);
 }
 
+bool Compiler::AnalyzeVariableScopeAccessHandler::handle_terminator(const SPIRBlock &block)
+{
+	switch (block.terminator)
+	{
+	case SPIRBlock::Return:
+		if (block.return_value)
+			notify_variable_access(block.return_value, block.self);
+		break;
+
+	case SPIRBlock::Select:
+	case SPIRBlock::MultiSelect:
+		notify_variable_access(block.condition, block.self);
+		break;
+
+	default:
+		break;
+	}
+
+	return true;
+}
+
 bool Compiler::AnalyzeVariableScopeAccessHandler::handle(spv::Op op, const uint32_t *args, uint32_t length)
 {
 	// Keep track of the types of temporaries, so we can hoist them out as necessary.

spirv_cross.hpp

@@ -765,6 +765,10 @@ protected:
 		// Return true if traversal should continue.
 		// If false, traversal will end immediately.
 		virtual bool handle(spv::Op opcode, const uint32_t *args, uint32_t length) = 0;
+		virtual bool handle_terminator(const SPIRBlock &)
+		{
+			return true;
+		}
 
 		virtual bool follow_function_call(const SPIRFunction &)
 		{
@@ -979,6 +983,7 @@ protected:
 		bool id_is_phi_variable(uint32_t id) const;
 		bool id_is_potential_temporary(uint32_t id) const;
 		bool handle(spv::Op op, const uint32_t *args, uint32_t length) override;
+		bool handle_terminator(const SPIRBlock &block) override;
 
 		Compiler &compiler;
 		SPIRFunction &entry;