agx: track block divergence

conservative for now. we'll need this for correctness.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36399>

src/asahi/compiler/agx_compile.c

@@ -2560,6 +2560,9 @@ agx_create_block(agx_context *ctx)
 {
    agx_block *blk = rzalloc(ctx, agx_block);
 
+   /* This is conservative, TODO: divergence analysis */
+   blk->divergent = ctx->total_nesting > 0;
+
    util_dynarray_init(&blk->predecessors, blk);
 
    return blk;

src/asahi/compiler/agx_compiler.h

@@ -452,6 +452,9 @@ typedef struct agx_block {
    struct util_dynarray predecessors;
    bool unconditional_jumps;
 
+   /* Could there be masked execution? */
+   bool divergent;
+
    /* Liveness analysis results */
    BITSET_WORD *live_in;
    BITSET_WORD *live_out;