On Mon, Aug 29, 2016 at 9:06 PM, Timothy Arceri <timothy.arc...@collabora.com> wrote: > Can't the phi have more than one source from before the loop? e.g > > int i = 0; > if (somthing) > i = 1; > else > i = 2; > > for ( ; i < 5; i++) > do_stuff(i);
In fact, no. :) NIR's control flow avoids so-called "critical edges" by ensuring that all if/else must be preceded by a single basic block and followed by a single basic block. It simplifies a lot of situations. This invariant and a few more are documented at the top of nir_control_flow.c. In your example, there will be a basic block between the end of the if/else construct and the beginning of the loop which will contain a phi node for i. phi nodes only have as many sources as its containing basic block has incoming edges. There are only two ways (that I can think of) that a block may have more than two incoming edges in NIR: multiple break or continue statements in a loop. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
