use first trailing one

Author: c8ef

libc/src/strings/CMakeLists.txt

@@ -60,6 +60,8 @@ add_entrypoint_object(
     ffs.cpp
   HDRS
     ffs.h
+  DEPENDS
+    libc.src.__support.math_extras
 )
 
 add_entrypoint_object(
@@ -68,6 +70,8 @@ add_entrypoint_object(
     ffsl.cpp
   HDRS
     ffsl.h
+  DEPENDS
+    libc.src.__support.math_extras
 )
 
 add_entrypoint_object(
@@ -76,6 +80,8 @@ add_entrypoint_object(
     ffsll.cpp
   HDRS
     ffsll.h
+  DEPENDS
+    libc.src.__support.math_extras
 )
 
 add_entrypoint_object(

libc/src/strings/ffs.cpp

@@ -9,9 +9,12 @@
 #include "src/strings/ffs.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/math_extras.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
-LLVM_LIBC_FUNCTION(int, ffs, (int i)) { return __builtin_ffs(i); }
+LLVM_LIBC_FUNCTION(int, ffs, (int i)) {
+  return first_trailing_one(static_cast<unsigned>(i));
+}
 
 } // namespace LIBC_NAMESPACE_DECL

libc/src/strings/ffsl.cpp

@@ -9,9 +9,12 @@
 #include "src/strings/ffsl.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/math_extras.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
-LLVM_LIBC_FUNCTION(int, ffsl, (long i)) { return __builtin_ffsl(i); }
+LLVM_LIBC_FUNCTION(int, ffsl, (long i)) {
+  return first_trailing_one(static_cast<unsigned long>(i));
+}
 
 } // namespace LIBC_NAMESPACE_DECL

libc/src/strings/ffsll.cpp

@@ -9,9 +9,12 @@
 #include "src/strings/ffsll.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/math_extras.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
-LLVM_LIBC_FUNCTION(int, ffsll, (long long i)) { return __builtin_ffsll(i); }
+LLVM_LIBC_FUNCTION(int, ffsll, (long long i)) {
+  return first_trailing_one(static_cast<unsigned long long>(i));
+}
 
 } // namespace LIBC_NAMESPACE_DECL

libc/test/src/strings/ffs_test.cpp

@@ -14,8 +14,15 @@
 namespace LIBC_NAMESPACE_DECL {
 
 TEST(LlvmLibcFfsTest, SimpleFfs) {
-  ASSERT_EQ(ffs(0), 0);
-  ASSERT_EQ(ffs(1), 1);
+  ASSERT_EQ(ffs(0x00000000), 0);
+  ASSERT_EQ(ffs(0x00000001), 1);
+  ASSERT_EQ(ffs(0x00000020), 6);
+  ASSERT_EQ(ffs(0x00000400), 11);
+  ASSERT_EQ(ffs(0x00008000), 16);
+  ASSERT_EQ(ffs(0x00010000), 17);
+  ASSERT_EQ(ffs(0x00200000), 22);
+  ASSERT_EQ(ffs(0x04000000), 27);
+  ASSERT_EQ(ffs(0x80000000), 32);
   ASSERT_EQ(ffs(0xfbe71), 1);
   ASSERT_EQ(ffs(0xfbe70), 5);
   ASSERT_EQ(ffs(0x10), 5);

libc/test/src/strings/ffsl_test.cpp

@@ -14,8 +14,23 @@
 namespace LIBC_NAMESPACE_DECL {
 
 TEST(LlvmLibcFfslTest, SimpleFfsl) {
-  ASSERT_EQ(ffsl(0L), 0);
-  ASSERT_EQ(ffsl(1L), 1);
+  ASSERT_EQ(ffsl(0x00000000L), 0);
+  ASSERT_EQ(ffsl(0x00000001L), 1);
+  ASSERT_EQ(ffsl(0x00000020L), 6);
+  ASSERT_EQ(ffsl(0x00000400L), 11);
+  ASSERT_EQ(ffsl(0x00008000L), 16);
+  ASSERT_EQ(ffsl(0x00010000L), 17);
+  ASSERT_EQ(ffsl(0x00200000L), 22);
+  ASSERT_EQ(ffsl(0x04000000L), 27);
+  ASSERT_EQ(ffsl(0x80000000L), 32);
+  ASSERT_EQ(ffsl(0x0000000100000000L), 33);
+  ASSERT_EQ(ffsl(0x0000002000000000L), 38);
+  ASSERT_EQ(ffsl(0x0000040000000000L), 43);
+  ASSERT_EQ(ffsl(0x0000800000000000L), 48);
+  ASSERT_EQ(ffsl(0x0001000000000000L), 49);
+  ASSERT_EQ(ffsl(0x0020000000000000L), 54);
+  ASSERT_EQ(ffsl(0x0400000000000000L), 59);
+  ASSERT_EQ(ffsl(0x8000000000000000L), 64);
   ASSERT_EQ(ffsl(0xfbe71L), 1);
   ASSERT_EQ(ffsl(0xfbe70L), 5);
   ASSERT_EQ(ffsl(0x10L), 5);

libc/test/src/strings/ffsll_test.cpp

@@ -14,8 +14,23 @@
 namespace LIBC_NAMESPACE_DECL {
 
 TEST(LlvmLibcFfsllTest, SimpleFfsll) {
-  ASSERT_EQ(ffsll(0LL), 0);
-  ASSERT_EQ(ffsll(1LL), 1);
+  ASSERT_EQ(ffsll(0x0000000000000000LL), 0);
+  ASSERT_EQ(ffsll(0x0000000000000001LL), 1);
+  ASSERT_EQ(ffsll(0x0000000000000020LL), 6);
+  ASSERT_EQ(ffsll(0x0000000000000400LL), 11);
+  ASSERT_EQ(ffsll(0x0000000000008000LL), 16);
+  ASSERT_EQ(ffsll(0x0000000000010000LL), 17);
+  ASSERT_EQ(ffsll(0x0000000000200000LL), 22);
+  ASSERT_EQ(ffsll(0x0000000004000000LL), 27);
+  ASSERT_EQ(ffsll(0x0000000080000000LL), 32);
+  ASSERT_EQ(ffsll(0x0000000100000000LL), 33);
+  ASSERT_EQ(ffsll(0x0000002000000000LL), 38);
+  ASSERT_EQ(ffsll(0x0000040000000000LL), 43);
+  ASSERT_EQ(ffsll(0x0000800000000000LL), 48);
+  ASSERT_EQ(ffsll(0x0001000000000000LL), 49);
+  ASSERT_EQ(ffsll(0x0020000000000000LL), 54);
+  ASSERT_EQ(ffsll(0x0400000000000000LL), 59);
+  ASSERT_EQ(ffsll(0x8000000000000000LL), 64);
   ASSERT_EQ(ffsll(0xfbe71LL), 1);
   ASSERT_EQ(ffsll(0xfbe70LL), 5);
   ASSERT_EQ(ffsll(0x10LL), 5);