From 23e1363d55ba0921473b195af104edce5c0d1ba0 Mon Sep 17 00:00:00 2001
From: Michael Wright <michaelwr@google.com>
Date: Sun, 12 Jul 2020 00:07:14 +0100
Subject: [PATCH] Cast away signedness of built-ins in BitSet.

Most of the built-in functions return signed values but BitSet deals
only in unsigned values. We can safely cast these away though as they're
always indices, which can't be negative.

Bug: 160010896
Test: atest inputflinger_tests, atest libinput_tests
Change-Id: I6e0b33972fabcd41ad1c269ea0e2a07b13b33c12
---
 libutils/include/utils/BitSet.h | 38 +++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/libutils/include/utils/BitSet.h b/libutils/include/utils/BitSet.h
index 8abfb1a07..1df46264f 100644
--- a/libutils/include/utils/BitSet.h
+++ b/libutils/include/utils/BitSet.h
@@ -46,7 +46,9 @@ struct BitSet32 {
     // Returns the number of marked bits in the set.
     inline uint32_t count() const { return count(value); }
 
-    static inline uint32_t count(uint32_t value) { return __builtin_popcountl(value); }
+    static inline uint32_t count(uint32_t value) {
+        return static_cast<uint32_t>(__builtin_popcountl(value));
+    }
 
     // Returns true if the bit set does not contain any marked bits.
     inline bool isEmpty() const { return isEmpty(value); }
@@ -128,7 +130,7 @@ struct BitSet32 {
     }
 
     static inline uint32_t getIndexOfBit(uint32_t value, uint32_t n) {
-        return __builtin_popcountl(value & ~(0xffffffffUL >> n));
+        return static_cast<uint32_t>(__builtin_popcountl(value & ~(0xffffffffUL >> n)));
     }
 
     inline bool operator== (const BitSet32& other) const { return value == other.value; }
@@ -153,17 +155,17 @@ private:
     // input, which is only guaranteed to be 16b, not 32. The compiler should optimize this away.
     static inline uint32_t clz_checked(uint32_t value) {
         if (sizeof(unsigned int) == sizeof(uint32_t)) {
-            return __builtin_clz(value);
+            return static_cast<uint32_t>(__builtin_clz(value));
         } else {
-            return __builtin_clzl(value);
+            return static_cast<uint32_t>(__builtin_clzl(value));
         }
     }
 
     static inline uint32_t ctz_checked(uint32_t value) {
         if (sizeof(unsigned int) == sizeof(uint32_t)) {
-            return __builtin_ctz(value);
+            return static_cast<uint32_t>(__builtin_ctz(value));
         } else {
-            return __builtin_ctzl(value);
+            return static_cast<uint32_t>(__builtin_ctzl(value));
         }
     }
 };
@@ -188,7 +190,9 @@ struct BitSet64 {
     // Returns the number of marked bits in the set.
     inline uint32_t count() const { return count(value); }
 
-    static inline uint32_t count(uint64_t value) { return __builtin_popcountll(value); }
+    static inline uint32_t count(uint64_t value) {
+        return static_cast<uint32_t>(__builtin_popcountll(value));
+    }
 
     // Returns true if the bit set does not contain any marked bits.
     inline bool isEmpty() const { return isEmpty(value); }
@@ -219,26 +223,32 @@ struct BitSet64 {
     // Result is undefined if all bits are unmarked.
     inline uint32_t firstMarkedBit() const { return firstMarkedBit(value); }
 
-    static inline uint32_t firstMarkedBit(uint64_t value) { return __builtin_clzll(value); }
+    static inline uint32_t firstMarkedBit(uint64_t value) {
+        return static_cast<uint32_t>(__builtin_clzll(value));
+    }
 
     // Finds the first unmarked bit in the set.
     // Result is undefined if all bits are marked.
     inline uint32_t firstUnmarkedBit() const { return firstUnmarkedBit(value); }
 
-    static inline uint32_t firstUnmarkedBit(uint64_t value) { return __builtin_clzll(~ value); }
+    static inline uint32_t firstUnmarkedBit(uint64_t value) {
+        return static_cast<uint32_t>(__builtin_clzll(~value));
+    }
 
     // Finds the last marked bit in the set.
     // Result is undefined if all bits are unmarked.
     inline uint32_t lastMarkedBit() const { return lastMarkedBit(value); }
 
-    static inline uint32_t lastMarkedBit(uint64_t value) { return 63 - __builtin_ctzll(value); }
+    static inline uint32_t lastMarkedBit(uint64_t value) {
+        return static_cast<uint32_t>(63 - __builtin_ctzll(value));
+    }
 
     // Finds the first marked bit in the set and clears it.  Returns the bit index.
     // Result is undefined if all bits are unmarked.
     inline uint32_t clearFirstMarkedBit() { return clearFirstMarkedBit(value); }
 
     static inline uint32_t clearFirstMarkedBit(uint64_t& value) {
-        uint64_t n = firstMarkedBit(value);
+        uint32_t n = firstMarkedBit(value);
         clearBit(value, n);
         return n;
     }
@@ -248,7 +258,7 @@ struct BitSet64 {
     inline uint32_t markFirstUnmarkedBit() { return markFirstUnmarkedBit(value); }
 
     static inline uint32_t markFirstUnmarkedBit(uint64_t& value) {
-        uint64_t n = firstUnmarkedBit(value);
+        uint32_t n = firstUnmarkedBit(value);
         markBit(value, n);
         return n;
     }
@@ -258,7 +268,7 @@ struct BitSet64 {
     inline uint32_t clearLastMarkedBit() { return clearLastMarkedBit(value); }
 
     static inline uint32_t clearLastMarkedBit(uint64_t& value) {
-        uint64_t n = lastMarkedBit(value);
+        uint32_t n = lastMarkedBit(value);
         clearBit(value, n);
         return n;
     }
@@ -268,7 +278,7 @@ struct BitSet64 {
     inline uint32_t getIndexOfBit(uint32_t n) const { return getIndexOfBit(value, n); }
 
     static inline uint32_t getIndexOfBit(uint64_t value, uint32_t n) {
-        return __builtin_popcountll(value & ~(0xffffffffffffffffULL >> n));
+        return static_cast<uint32_t>(__builtin_popcountll(value & ~(0xffffffffffffffffULL >> n)));
     }
 
     inline bool operator== (const BitSet64& other) const { return value == other.value; }