From 73169aa0b4efa81331e27521cfb28c4c8ba50fb6 Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Date: Wed, 30 Dec 2020 15:50:36 -0500
Subject: [PATCH] pan/bi: Stub FAU lowering pass

A given tuple can only load a single entry from FAU-RAM, so we need a
lowering pass before scheduling to assign FAU and lower the other
sources to moves.

Right now this only handles constants. Uniforms and general FAU are
todo.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8135>
---
 src/panfrost/bifrost/bifrost_compile.c | 51 ++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/src/panfrost/bifrost/bifrost_compile.c b/src/panfrost/bifrost/bifrost_compile.c
index 2a985d5cdad..dffbe32a8c3 100644
--- a/src/panfrost/bifrost/bifrost_compile.c
+++ b/src/panfrost/bifrost/bifrost_compile.c
@@ -3922,6 +3922,57 @@ glsl_type_size(const struct glsl_type *type, bool bindless)
         return glsl_count_attribute_slots(type, false);
 }
 
+static unsigned
+bi_lower_constant(bi_builder *b, bi_instr *ins, unsigned s, uint32_t *accum, unsigned cwords, bool allow_constant)
+{
+        uint32_t value = ins->src[s].value;
+
+        /* Staging registers can't have constants */
+        allow_constant &= !(s == 0 && bi_opcode_props[ins->op].sr_read);
+
+        /* If we're allowed any inline constants, see if this one works */
+        if (allow_constant) {
+                for (unsigned i = 0; i < cwords; ++i) {
+                        if (value == accum[i])
+                                return cwords;
+                }
+
+                if (value == 0 && !bi_opcode_props[ins->op].add)
+                        return cwords;
+
+                if (cwords < 2) {
+                        accum[cwords] = value;
+                        return cwords + 1;
+                }
+        }
+
+        /* should be const folded */
+        assert(!ins->src[s].abs && !ins->src[s].neg);
+        enum bi_swizzle old_swizzle = ins->src[s].swizzle;
+
+        b->cursor = bi_before_instr(ins);
+        ins->src[s] = bi_mov_i32(b, bi_imm_u32(value));
+        ins->src[s].swizzle = old_swizzle;
+        return cwords;
+}
+
+static void
+bi_lower_fau(bi_context *ctx, bi_block *block)
+{
+        bi_builder b = bi_init_builder(ctx);
+
+        bi_foreach_instr_in_block_safe(block, _ins) {
+                bi_instr *ins = (bi_instr *) _ins;
+                uint32_t constants[2];
+                unsigned cwords = 0;
+
+                bi_foreach_src(ins, s) {
+                        if (ins->src[s].type == BI_INDEX_CONSTANT)
+                                cwords = bi_lower_constant(&b, ins, s, constants, cwords, true);
+                }
+        }
+}
+
 static void
 bi_optimize_nir(nir_shader *nir)
 {