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[v2,1/4] riscv: Use builtins for the fmaximum and fminimum

Message ID 20260813142320.3617764-1-jz531210@gmail.com (mailing list archive)
State New
Headers
Series [v2,1/4] riscv: Use builtins for the fmaximum and fminimum |

Checks

Context Check Description
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linaro-tcwg-bot/tcwg_glibc_build--master-aarch64 success Build passed
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Commit Message

Julian Zhu Aug. 13, 2026, 2:23 p.m. UTC 
  Enable the fmax and fmin builtins for the fmaximum{_num} and fminimum{_num}.
The generic fmaximum{_num} and fminimum{_num} use them for ordered operands,
on rv64gc the double-precision functions drop from 21, 26, 23 and
29 instructions to 8, 8, 14 and 14.

fmax and fmin keep their own implementations, which need a signaling NaN
check because the instruction returns the number where C requires a
quiet NaN.  The headers live in rvd because without floating-point
registers GCC lowers the builtins to a call, which would recurse.

Signed-off-by: Julian Zhu <jz531210@gmail.com>
---
 sysdeps/riscv/rvd/math-use-builtins-fmax.h | 15 +++++++++++++++
 sysdeps/riscv/rvd/math-use-builtins-fmin.h | 15 +++++++++++++++
 2 files changed, 30 insertions(+)
 create mode 100644 sysdeps/riscv/rvd/math-use-builtins-fmax.h
 create mode 100644 sysdeps/riscv/rvd/math-use-builtins-fmin.h
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Patch

diff --git a/sysdeps/riscv/rvd/math-use-builtins-fmax.h b/sysdeps/riscv/rvd/math-use-builtins-fmax.h
new file mode 100644
index 0000000000..8865377475
--- /dev/null
+++ b/sysdeps/riscv/rvd/math-use-builtins-fmax.h
@@ -0,0 +1,15 @@ 
+/* This does not affect fmax and fmaxf, which have their own
+   implementations in rvd and rvf: the instruction returns the number for
+   a signaling NaN operand where C requires a quiet NaN, so they need an
+   explicit check.  Only the fmaximum and fminimum families and hypot use
+   these builtins.  */
+#if __GNUC_PREREQ (13, 0)
+# define USE_FMAX_BUILTIN 1
+# define USE_FMAXF_BUILTIN 1
+#else
+# define USE_FMAX_BUILTIN 0
+# define USE_FMAXF_BUILTIN 0
+#endif
+
+#define USE_FMAXL_BUILTIN 0
+#define USE_FMAXF128_BUILTIN 0
diff --git a/sysdeps/riscv/rvd/math-use-builtins-fmin.h b/sysdeps/riscv/rvd/math-use-builtins-fmin.h
new file mode 100644
index 0000000000..06e46bf7dd
--- /dev/null
+++ b/sysdeps/riscv/rvd/math-use-builtins-fmin.h
@@ -0,0 +1,15 @@ 
+/* This does not affect fmin and fminf, which have their own
+   implementations in rvd and rvf: the instruction returns the number for
+   a signaling NaN operand where C requires a quiet NaN, so they need an
+   explicit check.  Only the fmaximum and fminimum families and hypot use
+   these builtins.  */
+#if __GNUC_PREREQ (13, 0)
+# define USE_FMIN_BUILTIN 1
+# define USE_FMINF_BUILTIN 1
+#else
+# define USE_FMIN_BUILTIN 0
+# define USE_FMINF_BUILTIN 0
+#endif
+
+#define USE_FMINL_BUILTIN 0
+#define USE_FMINF128_BUILTIN 0