[libc-commits] [libc] [libc][math][c23] Finish optimizing fmul (PR #107517)

[Job Henandez Lara via libc-commits]

https://github.com/Jobhdez created https://github.com/llvm/llvm-project/pull/107517

None

>From 975bc84afea623831b71d70ec1a75fc6080c0a45 Mon Sep 17 00:00:00 2001
From: Job Hernandez <hj93 at protonmail.com>
Date: Thu, 5 Sep 2024 21:26:49 -0700
Subject: [PATCH] add draft, one more test to go

---
 libc/src/math/generic/CMakeLists.txt |  4 +++-
 libc/src/math/generic/fmul.cpp       | 18 ++++++++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 350072f4b9649d..5a1ee3b8b83c77 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -2958,7 +2958,9 @@ add_entrypoint_object(
   HDRS
     ../fmul.h
   DEPENDS
-    libc.src.__support.FPUtil.generic.mul
+    libc.hdr.errno_macros
+    libc.hdr.fenv_macros
+    libc.src.__support.FPUtil.double_double
   COMPILE_OPTIONS
     -O3
 )
diff --git a/libc/src/math/generic/fmul.cpp b/libc/src/math/generic/fmul.cpp
index 64c27d6e2f9564..fe8f5b0bb7c45b 100644
--- a/libc/src/math/generic/fmul.cpp
+++ b/libc/src/math/generic/fmul.cpp
@@ -5,16 +5,30 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-
+#include "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
 #include "src/math/fmul.h"
 #include "src/__support/FPUtil/generic/mul.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/FPUtil/double_double.h"
 
 namespace LIBC_NAMESPACE_DECL {
-
+  /*
 LLVM_LIBC_FUNCTION(float, fmul, (double x, double y)) {
   return fputil::generic::mul<float>(x, y);
 }
+  */
+LLVM_LIBC_FUNCTION(float, fmul, (double x, double y)) {
+  fputil::DoubleDouble prod = fputil::exact_mult(x, y);
+  if (LIBC_UNLIKELY(fputil::FPBits<double>(prod.hi).is_inf_or_nan() || fputil::FPBits<double>(prod.hi).is_zero()))
+    return static_cast<float>(prod.hi);
+  if (LIBC_UNLIKELY(fputil::FPBits<double>(prod.hi).is_inf() || fputil::FPBits<double>(prod.hi).is_zero())) {
+    fputil::set_errno_if_required(EDOM);
+    fputil::raise_except_if_required(FE_INVALID);
+    return fputil::FPBits<double>::quiet_nan().get_val();
+  }
+  return static_cast<float>(prod.hi + prod.lo);
+}
 
 } // namespace LIBC_NAMESPACE_DECL