From 3ffbf0cf6fc66bd134043736de61f677f5bb2030 Mon Sep 17 00:00:00 2001
From: David Michael Barr <b@rr-dav.id.au>
Date: Wed, 10 Feb 2021 15:08:58 +0900
Subject: [PATCH] Use explicit table lookup for ac_q and dc_q

Resolves an unusual compiler decision to invoke memmove.
---
 src/quantize.rs | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/src/quantize.rs b/src/quantize.rs
index f02d96eeab..dcea1fab74 100644
--- a/src/quantize.rs
+++ b/src/quantize.rs
@@ -32,25 +32,17 @@ pub fn get_log_tx_scale(tx_size: TxSize) -> usize {
 }
 
 pub fn dc_q(qindex: u8, delta_q: i8, bit_depth: usize) -> i16 {
-  let &table = match bit_depth {
-    8 => &dc_qlookup_Q3,
-    10 => &dc_qlookup_10_Q3,
-    12 => &dc_qlookup_12_Q3,
-    _ => unimplemented!(),
-  };
-
-  table[(qindex as isize + delta_q as isize).max(0).min(255) as usize]
+  static DC_Q: [&[i16; 256]; 3] =
+    [&dc_qlookup_Q3, &dc_qlookup_10_Q3, &dc_qlookup_12_Q3];
+  let bd = ((bit_depth ^ 8) >> 1).min(2);
+  DC_Q[bd][((qindex as isize + delta_q as isize).max(0) as usize).min(255)]
 }
 
 pub fn ac_q(qindex: u8, delta_q: i8, bit_depth: usize) -> i16 {
-  let &table = match bit_depth {
-    8 => &ac_qlookup_Q3,
-    10 => &ac_qlookup_10_Q3,
-    12 => &ac_qlookup_12_Q3,
-    _ => unimplemented!(),
-  };
-
-  table[(qindex as isize + delta_q as isize).max(0).min(255) as usize]
+  static AC_Q: [&[i16; 256]; 3] =
+    [&ac_qlookup_Q3, &ac_qlookup_10_Q3, &ac_qlookup_12_Q3];
+  let bd = ((bit_depth ^ 8) >> 1).min(2);
+  AC_Q[bd][((qindex as isize + delta_q as isize).max(0) as usize).min(255)]
 }
 
 // TODO: Handle lossless properly.