From 7e1e7be8fcd67884b881aaa1760914566e8356a5 Mon Sep 17 00:00:00 2001
From: Dave Rodgman <dave.rodgman@arm.com>
Date: Tue, 5 Sep 2023 18:12:33 +0100
Subject: [PATCH] Simplify fixes for unreachable code

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
---
 library/bignum_core.c | 35 +++++++----------------------------
 library/common.h      | 19 -------------------
 2 files changed, 7 insertions(+), 47 deletions(-)

diff --git a/library/bignum_core.c b/library/bignum_core.c
index 85dca5530..441151e66 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -77,40 +77,19 @@ size_t mbedtls_mpi_core_bitlen(const mbedtls_mpi_uint *A, size_t A_limbs)
     return 0;
 }
 
-/* Convert a big-endian byte array aligned to the size of mbedtls_mpi_uint
- * into the storage form used by mbedtls_mpi. */
-static mbedtls_mpi_uint mpi_bigendian_to_host_c(mbedtls_mpi_uint a)
-{
-    uint8_t i;
-    unsigned char *a_ptr;
-    mbedtls_mpi_uint tmp = 0;
-
-    for (i = 0, a_ptr = (unsigned char *) &a; i < ciL; i++, a_ptr++) {
-        tmp <<= CHAR_BIT;
-        tmp |= (mbedtls_mpi_uint) *a_ptr;
-    }
-
-    return tmp;
-}
-
 static mbedtls_mpi_uint mpi_bigendian_to_host(mbedtls_mpi_uint a)
 {
     if (MBEDTLS_IS_BIG_ENDIAN) {
         /* Nothing to do on bigendian systems. */
         return a;
     } else {
-MBEDTLS_IGNORE_UNREACHABLE_BEGIN
-        switch (sizeof(mbedtls_mpi_uint)) {
-            case 4:
-                return (mbedtls_mpi_uint) MBEDTLS_BSWAP32((uint32_t) a);
-            case 8:
-                return (mbedtls_mpi_uint) MBEDTLS_BSWAP64((uint64_t) a);
-        }
-
-        /* Fall back to C-based reordering if we don't know the byte order
-         * or we couldn't use a compiler-specific builtin. */
-        return mpi_bigendian_to_host_c(a);
-MBEDTLS_IGNORE_UNREACHABLE_END
+#if defined(MBEDTLS_HAVE_INT32)
+        return (mbedtls_mpi_uint) MBEDTLS_BSWAP32((uint32_t) a);
+#elif defined(MBEDTLS_HAVE_INT64)
+        return (mbedtls_mpi_uint) MBEDTLS_BSWAP64((uint64_t) a);
+#else
+#error "This is one of several places that need to be adapted to support a new limb size"
+#endif
     }
 }
 
diff --git a/library/common.h b/library/common.h
index 4e1b2fa2d..3c472c685 100644
--- a/library/common.h
+++ b/library/common.h
@@ -334,23 +334,4 @@ static inline void mbedtls_xor_no_simd(unsigned char *r,
 #define MBEDTLS_OPTIMIZE_FOR_PERFORMANCE
 #endif
 
-/* Define macros that can be used to disable warnings about unreachable code. */
-#if defined(__clang__)
-
-#define MBEDTLS_PRAGMA(x) _Pragma(#x)
-
-#define MBEDTLS_IGNORE_UNREACHABLE_BEGIN \
-    MBEDTLS_PRAGMA(clang diagnostic push) \
-    MBEDTLS_PRAGMA(clang diagnostic ignored "-Wunreachable-code")
-
-#define MBEDTLS_IGNORE_UNREACHABLE_END \
-    MBEDTLS_PRAGMA(clang diagnostic pop)
-
-#else
-
-#define MBEDTLS_IGNORE_UNREACHABLE_BEGIN
-#define MBEDTLS_IGNORE_UNREACHABLE_END
-
-#endif
-
 #endif /* MBEDTLS_LIBRARY_COMMON_H */