[PATCH] newlib: riscv: Remove unnecessary byte load for strlen()

[Eric Salem]

For architectures where XLEN is 32 bits, when detecting a null byte, a
word is read at a time. Once a null is found in the word, its precise
location is then determined. Make clear to the compiler that if the
first three bytes are not null, the last byte must be null, and does not
need to be read from the string, since its value is always zero.

Reviewed-by: Christian Herber <christian.herber@oss.nxp.com>
Signed-off-by: Eric Salem <ericsalem@gmail.com>
---
 newlib/libc/machine/riscv/strlen.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/newlib/libc/machine/riscv/strlen.c b/newlib/libc/machine/riscv/strlen.c
index 9bfd2a136753..9f1be1b0e70e 100644
--- a/newlib/libc/machine/riscv/strlen.c
+++ b/newlib/libc/machine/riscv/strlen.c
@@ -47,16 +47,16 @@ size_t strlen(const char *str)
     return ret + (psval >> 3) - sp;
   #else
     char c0 = str[0 - sp], c1 = str[1 - sp], c2 = str[2 - sp], c3 = str[3 - sp];
-    if (c0 == 0)    return ret + 0 - sp;
-    if (c1 == 0)    return ret + 1 - sp;
-    if (c2 == 0)    return ret + 2 - sp;
-    if (c3 == 0)    return ret + 3 - sp;
+    if (c0 == 0)                        return ret + 0 - sp;
+    if (c1 == 0)                        return ret + 1 - sp;
+    if (c2 == 0)                        return ret + 2 - sp;
+    if (__riscv_xlen == 32 || c3 == 0)  return ret + 3 - sp;
 
     #if __riscv_xlen == 64
       c0 = str[4 - sp], c1 = str[5 - sp], c2 = str[6 - sp];
-      if (c0 == 0)  return ret + 4 - sp;
-      if (c1 == 0)  return ret + 5 - sp;
-      if (c2 == 0)  return ret + 6 - sp;
+      if (c0 == 0)                      return ret + 4 - sp;
+      if (c1 == 0)                      return ret + 5 - sp;
+      if (c2 == 0)                      return ret + 6 - sp;
     #endif
 
     return ret + 7 - sp;
-- 
2.49.0