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[libc] implement strings/ffs #129892

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Merged
merged 6 commits into from
Mar 8, 2025
Merged

[libc] implement strings/ffs #129892

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6f2d8ef
implement ffs
c8ef Mar 5, 2025
a0e76ae
fix ci
c8ef Mar 5, 2025
f83e2c8
fix ci
c8ef Mar 5, 2025
5409f31
Merge branch 'main' into ffs
c8ef Mar 7, 2025
ccc7f83
use first trailing one
c8ef Mar 7, 2025
63bbca5
guard using LP64 since long could be 32bit
c8ef Mar 7, 2025
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6 changes: 6 additions & 0 deletions libc/src/strings/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,8 @@ add_entrypoint_object(
ffs.cpp
HDRS
ffs.h
DEPENDS
libc.src.__support.math_extras
)

add_entrypoint_object(
Expand All @@ -68,6 +70,8 @@ add_entrypoint_object(
ffsl.cpp
HDRS
ffsl.h
DEPENDS
libc.src.__support.math_extras
)

add_entrypoint_object(
Expand All @@ -76,6 +80,8 @@ add_entrypoint_object(
ffsll.cpp
HDRS
ffsll.h
DEPENDS
libc.src.__support.math_extras
)

add_entrypoint_object(
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5 changes: 4 additions & 1 deletion libc/src/strings/ffs.cpp
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Expand Up @@ -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
5 changes: 4 additions & 1 deletion libc/src/strings/ffsl.cpp
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Expand Up @@ -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
5 changes: 4 additions & 1 deletion libc/src/strings/ffsll.cpp
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Expand Up @@ -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
11 changes: 9 additions & 2 deletions libc/test/src/strings/ffs_test.cpp
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Expand Up @@ -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);
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19 changes: 17 additions & 2 deletions libc/test/src/strings/ffsl_test.cpp
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Expand Up @@ -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);
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@lntue lntue Mar 7, 2025

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Can you guard this part, because long might be 32-bit on some platforms.

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@c8ef c8ef Mar 7, 2025

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Ah, I almost forgot about this. Thanks for reminding me!

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);
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19 changes: 17 additions & 2 deletions libc/test/src/strings/ffsll_test.cpp
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Expand Up @@ -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);
Expand Down