[libc][stdfix] Add integer square root with fixed point output functi…

…ons. (#83959) Fix #83924.
llvm · Mar 6, 2024 · ad33fe1 · ad33fe1
1 parent ee1bcf7
commit ad33fe1
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Showing 20 changed files with 491 additions and 60 deletions.
diff --git a/libc/config/baremetal/api.td b/libc/config/baremetal/api.td
@@ -2,6 +2,7 @@ include "config/public_api.td"
 
 include "spec/stdc.td"
 include "spec/stdc_ext.td"
+include "spec/llvm_libc_ext.td"
 
 def AssertMacro : MacroDef<"assert"> {
   let Defn = [{

diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
@@ -306,6 +306,8 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
     libc.src.stdfix.sqrtur
     # libc.src.stdfix.sqrtulk
     libc.src.stdfix.sqrtulr
+    libc.src.stdfix.uhksqrtus
+    libc.src.stdfix.uksqrtui
   )
 endif()
 

diff --git a/libc/config/baremetal/riscv/entrypoints.txt b/libc/config/baremetal/riscv/entrypoints.txt
@@ -306,6 +306,8 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
     libc.src.stdfix.sqrtur
     # libc.src.stdfix.sqrtulk
     libc.src.stdfix.sqrtulr
+    libc.src.stdfix.uhksqrtus
+    libc.src.stdfix.uksqrtui
   )
 endif()
 

diff --git a/libc/config/linux/api.td b/libc/config/linux/api.td
@@ -5,8 +5,8 @@ include "spec/posix.td"
 include "spec/linux.td"
 include "spec/gnu_ext.td"
 include "spec/bsd_ext.td"
-include "spec/llvm_libc_ext.td"
 include "spec/stdc_ext.td"
+include "spec/llvm_libc_ext.td"
 
 def AssertMacro : MacroDef<"assert"> {
   let Defn = [{

diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -495,6 +495,8 @@ if(LIBC_COMPILER_HAS_FIXED_POINT)
     libc.src.stdfix.sqrtur
     # libc.src.stdfix.sqrtulk
     libc.src.stdfix.sqrtulr
+    libc.src.stdfix.uhksqrtus
+    libc.src.stdfix.uksqrtui
   )
 endif()
 

diff --git a/libc/docs/math/stdfix.rst b/libc/docs/math/stdfix.rst
@@ -4,14 +4,19 @@ StdFix Functions
 
 .. include:: ../check.rst
 
-Standards
----------
+Standards and Goals
+-------------------
 
 -   stdfix.h is specified in the `ISO/IEC TR 18037:2008 <https://www.iso.org/standard/51126.html>`_,
     C extensions to support embedded processors .
 
 -   Its `specifications <https://standards.iso.org/ittf/PubliclyAvailableStandards/c051126_ISO_IEC_TR_18037_2008.zip>`_.
 
+-   Our goal is to implement a complete set of math functions for fixed point
+    types, most of them are currently not included in the ISO/IEC TR
+    18037:2008 standard.  Our math functions for fixed point types are modeled
+    after the C99/C23 math functions for floating point types.
+
 ---------------
 Source location
 ---------------
@@ -53,6 +58,8 @@ Predefined Macros
 Fixed-point Arithmetics
 =======================
 
+The following functions are included in the ISO/IEC TR 18037:2008 standard.
+
 +---------------+------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------+
 | Function Name | _Fract (r)                                                                               | _Accum (k)                                                                               |
 |               +------------------------------+----------------------------+------------------------------+------------------------------+----------------------------+------------------------------+
@@ -78,8 +85,6 @@ Fixed-point Arithmetics
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 | round         | |check|        | |check|     | |check|       | |check|    | |check|        | |check|     | |check|        | |check|     | |check|       | |check|    | |check|        | |check|     |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
-| sqrt          | |check|        |             | |check|       |            | |check|        |             | |check|        |             | |check|       |            |                |             |
-+---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 
 ================== =========
 Type Generic Macro Available
@@ -93,6 +98,9 @@ roundfx
 Higher math functions
 =====================
 
+The following math functions are modeled after C99/C23 math functions for
+floating point types, but are not part of the ISO/IEC TR 18037:2008 spec.
+
 +---------------+------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------+
 | Function Name | _Fract (r)                                                                               | _Accum (k)                                                                               |
 |               +------------------------------+----------------------------+------------------------------+------------------------------+----------------------------+------------------------------+
@@ -108,13 +116,18 @@ Higher math functions
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 | sin           |                |             |               |            |                |             |                |             |               |            |                |             |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
+| sqrt          | |check|        |             | |check|       |            | |check|        |             | |check|        |             | |check|       |            |                |             |
++---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 | tan           |                |             |               |            |                |             |                |             |               |            |                |             |
 +---------------+----------------+-------------+---------------+------------+----------------+-------------+----------------+-------------+---------------+------------+----------------+-------------+
 
 
 Conversion Functions
 ====================
 
+The following conversion functions are included in the ISO/IEC TR 18037:2008
+standard.
+
 +---------------+------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------+
 | Function Name | _Fract (r)                                                                               | _Accum (k)                                                                               |
 |               +------------------------------+----------------------------+------------------------------+------------------------------+----------------------------+------------------------------+

diff --git a/libc/spec/llvm_libc_ext.td b/libc/spec/llvm_libc_ext.td
@@ -51,9 +51,29 @@ def LLVMLibcExt : StandardSpec<"llvm_libc_ext"> {
       ]
   >;
 
+  HeaderSpec StdFix = HeaderSpec<
+      "stdfix.h",
+      [],  // macros
+      [],  // types
+      [],  // enums
+      [    // functions
+          GuardedFunctionSpec<"sqrtuhr", RetValSpec<UnsignedShortFractType>, [ArgSpec<UnsignedShortFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"sqrtur", RetValSpec<UnsignedFractType>, [ArgSpec<UnsignedFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"sqrtulr", RetValSpec<UnsignedLongFractType>, [ArgSpec<UnsignedLongFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+
+          GuardedFunctionSpec<"sqrtuhk", RetValSpec<UnsignedShortAccumType>, [ArgSpec<UnsignedShortAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"sqrtuk", RetValSpec<UnsignedAccumType>, [ArgSpec<UnsignedAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"sqrtulk", RetValSpec<UnsignedLongAccumType>, [ArgSpec<UnsignedLongAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+
+          GuardedFunctionSpec<"uhksqrtus", RetValSpec<UnsignedShortAccumType>, [ArgSpec<UnsignedShortType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+          GuardedFunctionSpec<"uksqrtui", RetValSpec<UnsignedAccumType>, [ArgSpec<UnsignedIntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
+      ]
+  >;
+
   let Headers = [
-    Strings,
-    Sched,
     Assert,
+    Sched,
+    Stdfix,
+    Strings,
   ];
 }
diff --git a/libc/spec/stdc_ext.td b/libc/spec/stdc_ext.td
@@ -47,14 +47,6 @@ def StdcExt : StandardSpec<"stdc_ext"> {
           GuardedFunctionSpec<"rounduhk", RetValSpec<UnsignedShortAccumType>, [ArgSpec<UnsignedShortAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
           GuardedFunctionSpec<"rounduk", RetValSpec<UnsignedAccumType>, [ArgSpec<UnsignedAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
           GuardedFunctionSpec<"roundulk", RetValSpec<UnsignedLongAccumType>, [ArgSpec<UnsignedLongAccumType>, ArgSpec<IntType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
-
-          GuardedFunctionSpec<"sqrtuhr", RetValSpec<UnsignedShortFractType>, [ArgSpec<UnsignedShortFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
-          GuardedFunctionSpec<"sqrtur", RetValSpec<UnsignedFractType>, [ArgSpec<UnsignedFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
-          GuardedFunctionSpec<"sqrtulr", RetValSpec<UnsignedLongFractType>, [ArgSpec<UnsignedLongFractType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
-
-          GuardedFunctionSpec<"sqrtuhk", RetValSpec<UnsignedShortAccumType>, [ArgSpec<UnsignedShortAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
-          GuardedFunctionSpec<"sqrtuk", RetValSpec<UnsignedAccumType>, [ArgSpec<UnsignedAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
-          GuardedFunctionSpec<"sqrtulk", RetValSpec<UnsignedLongAccumType>, [ArgSpec<UnsignedLongAccumType>], "LIBC_COMPILER_HAS_FIXED_POINT">,
       ]
   >;
 

diff --git a/libc/src/__support/fixed_point/CMakeLists.txt b/libc/src/__support/fixed_point/CMakeLists.txt
@@ -32,5 +32,6 @@ add_header_library(
     libc.src.__support.macros.attributes
     libc.src.__support.macros.optimization
     libc.src.__support.CPP.bit
+    libc.src.__support.CPP.limits
     libc.src.__support.CPP.type_traits
 )
diff --git a/libc/src/__support/fixed_point/fx_rep.h b/libc/src/__support/fixed_point/fx_rep.h
@@ -48,6 +48,8 @@ template <> struct FXRep<short fract> {
   LIBC_INLINE static constexpr Type MAX() { return SFRACT_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0HR; }
   LIBC_INLINE static constexpr Type EPS() { return SFRACT_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5HR; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25HR; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_signed_t<StorageType>;
@@ -66,6 +68,8 @@ template <> struct FXRep<unsigned short fract> {
   LIBC_INLINE static constexpr Type MAX() { return USFRACT_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0UHR; }
   LIBC_INLINE static constexpr Type EPS() { return USFRACT_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5UHR; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25UHR; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_unsigned_t<StorageType>;
@@ -84,6 +88,8 @@ template <> struct FXRep<fract> {
   LIBC_INLINE static constexpr Type MAX() { return FRACT_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0R; }
   LIBC_INLINE static constexpr Type EPS() { return FRACT_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5R; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25R; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_signed_t<StorageType>;
@@ -102,6 +108,8 @@ template <> struct FXRep<unsigned fract> {
   LIBC_INLINE static constexpr Type MAX() { return UFRACT_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0UR; }
   LIBC_INLINE static constexpr Type EPS() { return UFRACT_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5UR; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25UR; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_unsigned_t<StorageType>;
@@ -120,6 +128,8 @@ template <> struct FXRep<long fract> {
   LIBC_INLINE static constexpr Type MAX() { return LFRACT_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0LR; }
   LIBC_INLINE static constexpr Type EPS() { return LFRACT_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5LR; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25LR; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_signed_t<StorageType>;
@@ -138,6 +148,8 @@ template <> struct FXRep<unsigned long fract> {
   LIBC_INLINE static constexpr Type MAX() { return ULFRACT_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0ULR; }
   LIBC_INLINE static constexpr Type EPS() { return ULFRACT_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5ULR; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25ULR; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_unsigned_t<StorageType>;
@@ -156,6 +168,8 @@ template <> struct FXRep<short accum> {
   LIBC_INLINE static constexpr Type MAX() { return SACCUM_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0HK; }
   LIBC_INLINE static constexpr Type EPS() { return SACCUM_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5HK; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25HK; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_signed_t<StorageType>;
@@ -174,6 +188,8 @@ template <> struct FXRep<unsigned short accum> {
   LIBC_INLINE static constexpr Type MAX() { return USACCUM_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0UHK; }
   LIBC_INLINE static constexpr Type EPS() { return USACCUM_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5UHK; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25UHK; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_unsigned_t<StorageType>;
@@ -192,6 +208,8 @@ template <> struct FXRep<accum> {
   LIBC_INLINE static constexpr Type MAX() { return ACCUM_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0K; }
   LIBC_INLINE static constexpr Type EPS() { return ACCUM_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5K; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25K; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_signed_t<StorageType>;
@@ -210,6 +228,8 @@ template <> struct FXRep<unsigned accum> {
   LIBC_INLINE static constexpr Type MAX() { return UACCUM_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0UK; }
   LIBC_INLINE static constexpr Type EPS() { return UACCUM_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5UK; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25UK; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_unsigned_t<StorageType>;
@@ -228,6 +248,8 @@ template <> struct FXRep<long accum> {
   LIBC_INLINE static constexpr Type MAX() { return LACCUM_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0LK; }
   LIBC_INLINE static constexpr Type EPS() { return LACCUM_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5LK; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25LK; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_signed_t<StorageType>;
@@ -246,6 +268,8 @@ template <> struct FXRep<unsigned long accum> {
   LIBC_INLINE static constexpr Type MAX() { return ULACCUM_MIN; }
   LIBC_INLINE static constexpr Type ZERO() { return 0.0ULK; }
   LIBC_INLINE static constexpr Type EPS() { return ULACCUM_EPSILON; }
+  LIBC_INLINE static constexpr Type ONE_HALF() { return 0.5ULK; }
+  LIBC_INLINE static constexpr Type ONE_FOURTH() { return 0.25ULK; }
 
   using StorageType = typename internal::Storage<TOTAL_LEN>::Type;
   using CompType = cpp::make_unsigned_t<StorageType>;