pan/bi: Add fexp2 implementation

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4615>

src/panfrost/Makefile.sources

@@ -5,6 +5,7 @@ bifrost_FILES := \
         bifrost/bi_lower_combine.c \
         bifrost/bi_tables.c \
         bifrost/bi_schedule.c \
+        bifrost/bi_special.c \
         bifrost/bi_print.c \
         bifrost/bi_print.h \
         bifrost/bi_quirks.h \

src/panfrost/bifrost/bi_special.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2020 Collabora Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Authors (Collabora):
+ *      Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
+ */
+
+#include "compiler.h"
+
+/* Bifrost requires special functions to be lowered in various machine specific
+ * ways. The routines in this file are used in codegen for this. */
+
+/* New Bifrost has a FEXP2_FAST instruction but requires an auxiliary
+ * parameter. */
+
+static void
+bi_emit_fexp2_new(bi_context *ctx, nir_alu_instr *instr)
+{
+        /* FMA_MSCALE T, X, 1.0, 0, 0x18 */
+
+        bi_instruction mscale = {
+                .type = BI_FMA,
+                .op = { .mscale = true },
+                .dest = bi_make_temp(ctx),
+                .dest_type = nir_type_float32,
+                .writemask = 0xF,
+                .src = {
+                        bir_src_index(&instr->src[0].src),
+                        BIR_INDEX_CONSTANT | 0,
+                        BIR_INDEX_ZERO,
+                        BIR_INDEX_CONSTANT | 32,
+                },
+                .src_types = {
+                        nir_type_float32,
+                        nir_type_float32,
+                        nir_type_float32,
+                        nir_type_int32,
+                },
+                .constant = {
+                        /* 0x3f80000000 = 1.0f as fp32
+                         * 24 = shift to multiply by 2^24 */
+                        .u64 = (0x3f800000) | (24ull << 32)
+                }
+        };
+
+        /* F2I_RTE T, T */
+
+        bi_instruction f2i = {
+                .type = BI_CONVERT,
+                .dest = bi_make_temp(ctx),
+                .dest_type = nir_type_int32,
+                .writemask = 0xF,
+                .src = { mscale.dest },
+                .src_types = { nir_type_float32 },
+                .roundmode = BIFROST_RTE
+        };
+
+        /* FEXP2_FAST T, T, X */
+
+        bi_instruction fexp = {
+                .type = BI_SPECIAL,
+                .op = { .special = BI_SPECIAL_EXP2_LOW },
+                .dest = bir_dest_index(&instr->dest.dest),
+                .dest_type = nir_type_float32,
+                .writemask = 0xF,
+                .src = { f2i.dest, mscale.src[0] },
+                .src_types = { nir_type_int32, nir_type_float32 },
+        };
+
+        bi_emit(ctx, mscale);
+        bi_emit(ctx, f2i);
+        bi_emit(ctx, fexp);
+}
+
+void
+bi_emit_fexp2(bi_context *ctx, nir_alu_instr *instr)
+{
+        /* TODO: G71 */
+        bi_emit_fexp2_new(ctx, instr);
+}

src/panfrost/bifrost/bifrost_compile.c

@@ -526,7 +526,16 @@ bi_fuse_csel_cond(bi_instruction *csel, nir_alu_src cond,
 static void
 emit_alu(bi_context *ctx, nir_alu_instr *instr)
 {
-        /* Assume it's something we can handle normally */
+        /* Try some special functions */
+        switch (instr->op) {
+        case nir_op_fexp2:
+                bi_emit_fexp2(ctx, instr);
+                return;
+        default:
+                break;
+        }
+
+        /* Otherwise, assume it's something we can handle normally */
         bi_instruction alu = {
                 .type = bi_class_for_nir_alu(instr->op),
                 .dest = bir_dest_index(&instr->dest.dest),

src/panfrost/bifrost/compiler.h

@@ -558,6 +558,10 @@ pan_next_block(pan_block *block)
         return list_first_entry(&(block->link), pan_block, link);
 }
 
+/* Special functions */
+
+void bi_emit_fexp2(bi_context *ctx, nir_alu_instr *instr);
+
 /* BIR manipulation */
 
 bool bi_has_outmod(bi_instruction *ins);

src/panfrost/bifrost/meson.build

@@ -28,6 +28,7 @@ libpanfrost_bifrost_files = files(
   'bi_pack.c',
   'bi_ra.c',
   'bi_schedule.c',
+  'bi_special.c',
   'bi_tables.c',
   'bir.c',
   'bifrost_compile.c',