[libc][math] Implement fast pass for double precision atan2 with 1 ULP errors. (#100648)

Author: lntue

libc/config/darwin/arm/entrypoints.txt

@@ -120,6 +120,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.acoshf
     libc.src.math.asinf
     libc.src.math.asinhf
+    libc.src.math.atan2
     libc.src.math.atan2f
     libc.src.math.atanf
     libc.src.math.atanhf

libc/config/linux/aarch64/entrypoints.txt

@@ -343,6 +343,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.acoshf
     libc.src.math.asinf
     libc.src.math.asinhf
+    libc.src.math.atan2
     libc.src.math.atan2f
     libc.src.math.atanf
     libc.src.math.atanhf

libc/config/linux/arm/entrypoints.txt

@@ -213,6 +213,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.acoshf
     libc.src.math.asinf
     libc.src.math.asinhf
+    libc.src.math.atan2
     libc.src.math.atan2f
     libc.src.math.atanf
     libc.src.math.atanhf

libc/config/linux/riscv/entrypoints.txt

@@ -365,6 +365,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.acoshf
     libc.src.math.asinf
     libc.src.math.asinhf
+    libc.src.math.atan2
     libc.src.math.atan2f
     libc.src.math.atanf
     libc.src.math.atanhf

libc/config/linux/x86_64/entrypoints.txt

@@ -365,6 +365,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.acoshf
     libc.src.math.asinf
     libc.src.math.asinhf
+    libc.src.math.atan2
     libc.src.math.atan2f
     libc.src.math.atanf
     libc.src.math.atanhf

libc/config/windows/entrypoints.txt

@@ -118,6 +118,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.acoshf
     libc.src.math.asinf
     libc.src.math.asinhf
+    libc.src.math.atan2
     libc.src.math.atan2f
     libc.src.math.atanf
     libc.src.math.atanhf

libc/docs/math/index.rst

@@ -260,7 +260,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | atan      | |check|          |                 |                        |                      |                        | 7.12.4.3               | F.10.1.3                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| atan2     | |check|          |                 |                        |                      |                        | 7.12.4.4               | F.10.1.4                   |
+| atan2     | |check|          | 1 ULP           |                        |                      |                        | 7.12.4.4               | F.10.1.4                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | atan2pi   |                  |                 |                        |                      |                        | 7.12.4.11              | F.10.1.11                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

libc/spec/stdc.td

@@ -692,6 +692,7 @@ def StdC : StandardSpec<"stdc"> {
 
           FunctionSpec<"atanf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
 
+          FunctionSpec<"atan2", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>]>,
           FunctionSpec<"atan2f", RetValSpec<FloatType>, [ArgSpec<FloatType>, ArgSpec<FloatType>]>,
 
           FunctionSpec<"acoshf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,

libc/src/math/generic/CMakeLists.txt

@@ -3848,6 +3848,26 @@ add_entrypoint_object(
     libc.src.__support.macros.optimization
 )
 
+add_entrypoint_object(
+  atan2
+  SRCS
+    atan2.cpp
+  HDRS
+    ../atan2.h
+  COMPILE_OPTIONS
+    -O3
+  DEPENDS
+    .inv_trigf_utils
+    libc.src.__support.FPUtil.double_double
+    libc.src.__support.FPUtil.dyadic_float
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.multiply_add
+    libc.src.__support.FPUtil.nearest_integer
+    libc.src.__support.FPUtil.polyeval
+    libc.src.__support.FPUtil.rounding_mode
+    libc.src.__support.macros.optimization
+)
+
 add_entrypoint_object(
   scalblnf16
   SRCS