pan/bi: Add support for if-else blocks
Branch lowering code lifted from Midgard as usual. Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4097>
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@ -52,10 +52,38 @@ create_empty_block(bi_context *ctx)
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return blk;
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}
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static void
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bi_block_add_successor(bi_block *block, bi_block *successor)
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{
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assert(block);
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assert(successor);
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for (unsigned i = 0; i < ARRAY_SIZE(block->successors); ++i) {
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if (block->successors[i]) {
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if (block->successors[i] == successor)
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return;
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else
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continue;
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}
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block->successors[i] = successor;
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_mesa_set_add(successor->predecessors, block);
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return;
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}
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unreachable("Too many successors");
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}
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static bi_block *
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emit_block(bi_context *ctx, nir_block *block)
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{
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ctx->current_block = create_empty_block(ctx);
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if (ctx->after_block) {
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ctx->current_block = ctx->after_block;
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ctx->after_block = NULL;
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} else {
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ctx->current_block = create_empty_block(ctx);
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}
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list_addtail(&ctx->current_block->link, &ctx->blocks);
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list_inithead(&ctx->current_block->instructions);
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@ -67,6 +95,85 @@ emit_block(bi_context *ctx, nir_block *block)
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return ctx->current_block;
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}
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/* Emits an unconditional branch to the end of the current block, returning a
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* pointer so the user can fill in details */
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static bi_instruction *
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bi_emit_branch(bi_context *ctx)
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{
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bi_instruction branch = {
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.type = BI_BRANCH,
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.branch = {
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.cond = BI_COND_ALWAYS
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}
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};
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return bi_emit(ctx, branch);
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}
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/* Sets a condition for a branch by examing the NIR condition. If we're
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* familiar with the condition, we unwrap it to fold it into the branch
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* instruction. Otherwise, we consume the condition directly. We
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* generally use 1-bit booleans which allows us to use small types for
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* the conditions.
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*/
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static void
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bi_set_branch_cond(bi_instruction *branch, nir_src *cond, bool invert)
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{
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/* TODO: Try to unwrap instead of always bailing */
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branch->src[0] = bir_src_index(cond);
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branch->src[1] = BIR_INDEX_ZERO;
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branch->src_types[0] = branch->src_types[1] = nir_type_uint16;
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branch->branch.cond = invert ? BI_COND_EQ : BI_COND_NE;
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}
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static void
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emit_if(bi_context *ctx, nir_if *nif)
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{
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bi_block *before_block = ctx->current_block;
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/* Speculatively emit the branch, but we can't fill it in until later */
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bi_instruction *then_branch = bi_emit_branch(ctx);
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bi_set_branch_cond(then_branch, &nif->condition, true);
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/* Emit the two subblocks. */
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bi_block *then_block = emit_cf_list(ctx, &nif->then_list);
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bi_block *end_then_block = ctx->current_block;
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/* Emit a jump from the end of the then block to the end of the else */
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bi_instruction *then_exit = bi_emit_branch(ctx);
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/* Emit second block, and check if it's empty */
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int count_in = ctx->instruction_count;
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bi_block *else_block = emit_cf_list(ctx, &nif->else_list);
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bi_block *end_else_block = ctx->current_block;
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ctx->after_block = create_empty_block(ctx);
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/* Now that we have the subblocks emitted, fix up the branches */
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assert(then_block);
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assert(else_block);
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if (ctx->instruction_count == count_in) {
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/* The else block is empty, so don't emit an exit jump */
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bi_remove_instruction(then_exit);
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then_branch->branch.target = ctx->after_block;
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} else {
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then_branch->branch.target = else_block;
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then_exit->branch.target = ctx->after_block;
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bi_block_add_successor(end_then_block, then_exit->branch.target);
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}
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/* Wire up the successors */
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bi_block_add_successor(before_block, then_branch->branch.target); /* then_branch */
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bi_block_add_successor(before_block, then_block); /* fallthrough */
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bi_block_add_successor(end_else_block, ctx->after_block); /* fallthrough */
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}
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static bi_block *
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emit_cf_list(bi_context *ctx, struct exec_list *list)
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{
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@ -83,11 +190,11 @@ emit_cf_list(bi_context *ctx, struct exec_list *list)
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break;
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}
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#if 0
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case nir_cf_node_if:
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emit_if(ctx, nir_cf_node_as_if(node));
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break;
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#if 0
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case nir_cf_node_loop:
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emit_loop(ctx, nir_cf_node_as_loop(node));
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break;
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