Provide optimised bn_subw() and bn_subw_subw() for arm.

1 files changed, 50 insertions, 1 deletions

diff --git a/src/lib/libcrypto/bn/arch/arm/bn_arch.h b/src/lib/libcrypto/bn/arch/arm/bn_arch.h
index 136adf0e97..ef9bf7f156 100644
--- a/src/lib/libcrypto/bn/arch/arm/bn_arch.h
+++ b/src/lib/libcrypto/bn/arch/arm/bn_arch.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bn_arch.h,v 1.1 2023/01/20 10:04:33 jsing Exp $ */
+/*      $OpenBSD: bn_arch.h,v 1.2 2023/06/24 15:51:47 jsing Exp $ */
 /*
  * Copyright (c) 2023 Joel Sing <jsing@openbsd.org>
  *
@@ -15,10 +15,59 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <openssl/bn.h>
+
 #ifndef HEADER_BN_ARCH_H
 #define HEADER_BN_ARCH_H
 
 #ifndef OPENSSL_NO_ASM
 
+#if defined(__GNUC__)
+
+#define HAVE_BN_SUBW
+
+static inline void
+bn_subw(BN_ULONG a, BN_ULONG b, BN_ULONG *out_borrow, BN_ULONG *out_r0)
+{
+        BN_ULONG borrow, r0;
+
+        __asm__ (
+            "mov  %[borrow], #0 \n"
+            "subs %[r0], %[a], %[b] \n"
+            "sbc  %[borrow], %[borrow], #0 \n"
+            "neg  %[borrow], %[borrow] \n"
+            : [borrow]"=&r"(borrow), [r0]"=r"(r0)
+            : [a]"r"(a), [b]"r"(b)
+            : "cc");
+
+        *out_borrow = borrow;
+        *out_r0 = r0;
+}
+
+#define HAVE_BN_SUBW_SUBW
+
+static inline void
+bn_subw_subw(BN_ULONG a, BN_ULONG b, BN_ULONG c, BN_ULONG *out_borrow,
+    BN_ULONG *out_r0)
+{
+        BN_ULONG borrow, r0;
+
+        __asm__ (
+            "mov  %[borrow], #0 \n"
+            "subs %[r0], %[a], %[b] \n"
+            "sbc  %[borrow], %[borrow], #0 \n"
+            "subs %[r0], %[r0], %[c] \n"
+            "sbc  %[borrow], %[borrow], #0 \n"
+            "neg  %[borrow], %[borrow] \n"
+            : [borrow]"=&r"(borrow), [r0]"=&r"(r0)
+            : [a]"r"(a), [b]"r"(b), [c]"r"(c)
+            : "cc");
+
+        *out_borrow = borrow;
+        *out_r0 = r0;
+}
+
+#endif /* __GNUC__ */
+
 #endif
 #endif