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added description of control flow behavior (wrote this text at 34C3, not sure why I didn't post it at the time, it would be good if someone could independently verify it all)
1.0 can be multiplied 63 times by 0.5 until the result compares equal zero. This is consistent with a 7-bit exponent and output subnormal flushing.
1.0 can be multiplied 63 times by 0.5 until the result compares equal zero. This is consistent with a 7-bit exponent and output subnormal flushing.
== Control Flow ==
Control flow is implemented using three independent stacks: an 8-deep IF stack, a 4-deep CALL stack, and a 4-deep LOOP stack. All stacks are initially empty. After every instruction, the stacks are checked in the order CALL->IF->LOOP and if a stack is popped, the program counter update overwrites any previous update, even if set by a JMP instruction. The IF/LOOP stacks can only pop one entry per instruction, whereas the CALL stack can be completely emptied. If the CALL stack is popped four times in a single instruction, the last program counter update is missed. Executing a BREAK on an empty LOOP stack hangs the GPU. The stacks are actually ring buffers: overflow overwrites the oldest entry, the stack size is clamped.