From 94f2be5473182789ec3f6388b43fcd708a505500 Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow <fsahmkow27@gmail.com>
Date: Fri, 10 May 2019 22:12:35 -0400
Subject: texture_cache: Optimize GetMipBlockHeight and GetMipBlockDepth

---
 src/common/bit_util.h                           | 44 +++++++++++++++++++++++++
 src/video_core/texture_cache/surface_params.cpp | 19 ++++-------
 2 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/src/common/bit_util.h b/src/common/bit_util.h
index d032df413..6f7d5a947 100644
--- a/src/common/bit_util.h
+++ b/src/common/bit_util.h
@@ -97,4 +97,48 @@ inline u32 CountTrailingZeroes64(u64 value) {
 }
 #endif
 
+#ifdef _MSC_VER
+
+inline u32 MostSignificantBit32(const u32 value) {
+    unsigned long result;
+    _BitScanReverse(&result, value);
+    return static_cast<u32>(result);
+}
+
+inline u32 MostSignificantBit64(const u64 value) {
+    unsigned long result;
+    _BitScanReverse64(&result, value);
+    return static_cast<u32>(result);
+}
+
+#else
+
+inline u32 MostSignificantBit32(const u32 value) {
+    return 31U - static_cast<u32>(__builtin_clz(value));
+}
+
+inline u32 MostSignificantBit64(const u64 value) {
+    return 63U - static_cast<u32>(__builtin_clzll(value));
+}
+
+#endif
+
+inline u32 Log2Floor32(const u32 value) {
+    return MostSignificantBit32(value);
+}
+
+inline u32 Log2Ceil32(const u32 value) {
+    const u32 log2_f = Log2Floor32(value);
+    return log2_f + ((value ^ (1U << log2_f)) != 0U);
+}
+
+inline u32 Log2Floor64(const u64 value) {
+    return MostSignificantBit64(value);
+}
+
+inline u32 Log2Ceil64(const u64 value) {
+    const u64 log2_f = static_cast<u64>(Log2Floor64(value));
+    return static_cast<u32>(log2_f + ((value ^ (1ULL << log2_f)) != 0ULL));
+}
+
 } // namespace Common
diff --git a/src/video_core/texture_cache/surface_params.cpp b/src/video_core/texture_cache/surface_params.cpp
index 3a47f404d..e7e671d8c 100644
--- a/src/video_core/texture_cache/surface_params.cpp
+++ b/src/video_core/texture_cache/surface_params.cpp
@@ -5,6 +5,7 @@
 #include <map>
 
 #include "common/alignment.h"
+#include "common/bit_util.h"
 #include "common/cityhash.h"
 #include "core/core.h"
 #include "video_core/engines/shader_bytecode.h"
@@ -190,11 +191,8 @@ u32 SurfaceParams::GetMipBlockHeight(u32 level) const {
     const u32 height{GetMipHeight(level)};
     const u32 default_block_height{GetDefaultBlockHeight()};
     const u32 blocks_in_y{(height + default_block_height - 1) / default_block_height};
-    u32 block_height = 4;
-    while (block_height > 0 && blocks_in_y <= (1U << block_height) * 4) {
-        --block_height;
-    }
-    return block_height;
+    const u32 block_height = Common::Log2Ceil32(blocks_in_y);
+    return std::clamp(block_height, 3U, 8U) - 3U;
 }
 
 u32 SurfaceParams::GetMipBlockDepth(u32 level) const {
@@ -206,15 +204,10 @@ u32 SurfaceParams::GetMipBlockDepth(u32 level) const {
     }
 
     const u32 depth{GetMipDepth(level)};
-    u32 block_depth = 5;
-    while (block_depth > 0 && depth * 2 <= (1U << block_depth)) {
-        --block_depth;
-    }
-
-    if (block_depth == 5 && GetMipBlockHeight(level) >= 2) {
-        return 4;
+    const u32 block_depth = Common::Log2Ceil32(depth);
+    if (block_depth > 4) {
+        return 5 - (GetMipBlockHeight(level) >= 2);
     }
-
     return block_depth;
 }
 
-- 
cgit v1.2.3