GPU/Shaders: Implemented SSY and SYNC as a way to modify control flow during shader execution.
SSY sets the target label to jump to when the SYNC instruction is executed.
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@ -141,6 +141,15 @@ private:
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ExitMethod jmp = Scan(target, end, labels);
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return exit_method = ParallelExit(no_jmp, jmp);
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}
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case OpCode::Id::SSY: {
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// The SSY instruction uses a similar encoding as the BRA instruction.
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ASSERT_MSG(instr.bra.constant_buffer == 0,
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"Constant buffer SSY is not supported");
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u32 target = offset + instr.bra.GetBranchTarget();
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labels.insert(target);
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// Continue scanning for an exit method.
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break;
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}
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}
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}
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}
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@ -1668,16 +1677,25 @@ private:
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break;
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}
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case OpCode::Id::SSY: {
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// The SSY opcode tells the GPU where to re-converge divergent execution paths, we
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// can ignore this when generating GLSL code.
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// The SSY opcode tells the GPU where to re-converge divergent execution paths, it
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// sets the target of the jump that the SYNC instruction will make. The SSY opcode
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// has a similar structure to the BRA opcode.
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ASSERT_MSG(instr.bra.constant_buffer == 0, "Constant buffer SSY is not supported");
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u32 target = offset + instr.bra.GetBranchTarget();
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shader.AddLine("ssy_target = " + std::to_string(target) + "u;");
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break;
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}
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case OpCode::Id::SYNC:
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case OpCode::Id::SYNC: {
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// The SYNC opcode jumps to the address previously set by the SSY opcode
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ASSERT(instr.flow.cond == Tegra::Shader::FlowCondition::Always);
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shader.AddLine("{ jmp_to = ssy_target; break; }");
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break;
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}
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case OpCode::Id::DEPBAR: {
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// TODO(Subv): Find out if we actually have to care about these instructions or if
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// TODO(Subv): Find out if we actually have to care about this instruction or if
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// the GLSL compiler takes care of that for us.
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LOG_WARNING(HW_GPU, "DEPBAR/SYNC instruction is stubbed");
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LOG_WARNING(HW_GPU, "DEPBAR instruction is stubbed");
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break;
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}
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default: {
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@ -1742,6 +1760,7 @@ private:
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} else {
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labels.insert(subroutine.begin);
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shader.AddLine("uint jmp_to = " + std::to_string(subroutine.begin) + "u;");
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shader.AddLine("uint ssy_target = 0u;");
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shader.AddLine("while (true) {");
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++shader.scope;
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@ -1757,7 +1776,7 @@ private:
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u32 compile_end = CompileRange(label, next_label);
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if (compile_end > next_label && compile_end != PROGRAM_END) {
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// This happens only when there is a label inside a IF/LOOP block
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shader.AddLine("{ jmp_to = " + std::to_string(compile_end) + "u; break; }");
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shader.AddLine(" jmp_to = " + std::to_string(compile_end) + "u; break; }");
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labels.emplace(compile_end);
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}
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