[libc][riscv] Check if we have F or D extension before using them

[petrhosek]

We shouldn't be using instructions that require F or D extensions unconditionally before checking if those instructions are available.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Petr Hosek (petrhosek)

Changes

We shouldn't be using instructions that require F or D extensions unconditionally before checking if those instructions are available.

---

Full diff: https://github.com/llvm/llvm-project/pull/79036.diff

2 Files Affected:

• (modified) libc/src/__support/FPUtil/riscv/FMA.h (+4)
• (modified) libc/src/__support/FPUtil/riscv/sqrt.h (+4)

diff --git a/libc/src/__support/FPUtil/riscv/FMA.h b/libc/src/__support/FPUtil/riscv/FMA.h
index 32bef1ea8843e15..1dd7c8c9a462d41 100644
--- a/libc/src/__support/FPUtil/riscv/FMA.h
+++ b/libc/src/__support/FPUtil/riscv/FMA.h
@@ -26,6 +26,7 @@
 namespace LIBC_NAMESPACE {
 namespace fputil {
 
+#if defined(__riscv_flen)
 template <typename T>
 LIBC_INLINE cpp::enable_if_t<cpp::is_same_v<T, float>, T> fma(T x, T y, T z) {
   float result;
@@ -35,6 +36,7 @@ LIBC_INLINE cpp::enable_if_t<cpp::is_same_v<T, float>, T> fma(T x, T y, T z) {
   return result;
 }
 
+#if __riscv_flen == 64
 template <typename T>
 LIBC_INLINE cpp::enable_if_t<cpp::is_same_v<T, double>, T> fma(T x, T y, T z) {
   double result;
@@ -43,6 +45,8 @@ LIBC_INLINE cpp::enable_if_t<cpp::is_same_v<T, double>, T> fma(T x, T y, T z) {
                   : "f"(x), "f"(y), "f"(z));
   return result;
 }
+#endif // __riscv_flen == 64
+#endif // defined(__riscv_flen)
 
 } // namespace fputil
 } // namespace LIBC_NAMESPACE
diff --git a/libc/src/__support/FPUtil/riscv/sqrt.h b/libc/src/__support/FPUtil/riscv/sqrt.h
index a42687004639b4b..5ab027e617cc18a 100644
--- a/libc/src/__support/FPUtil/riscv/sqrt.h
+++ b/libc/src/__support/FPUtil/riscv/sqrt.h
@@ -21,17 +21,21 @@
 namespace LIBC_NAMESPACE {
 namespace fputil {
 
+#if defined(__riscv_flen)
 template <> LIBC_INLINE float sqrt<float>(float x) {
   float result;
   __asm__ __volatile__("fsqrt.s %0, %1\n\t" : "=f"(result) : "f"(x));
   return result;
 }
 
+#if __riscv_flen == 64
 template <> LIBC_INLINE double sqrt<double>(double x) {
   double result;
   __asm__ __volatile__("fsqrt.d %0, %1\n\t" : "=f"(result) : "f"(x));
   return result;
 }
+#endif // __riscv_flen == 64
+#endif // defined(__riscv_flen)
 
 } // namespace fputil
 } // namespace LIBC_NAMESPACE

[nickdesaulniers]

unless you have a more complex expression, stick with #ifdef

[petrhosek]

Done.