implement memset and memclr as well; reimplement memclr4 and memset4

Author: japaric

src/arm.rs

@@ -1,7 +1,7 @@
 use core::intrinsics;
 
 #[cfg(feature = "mem")]
-use mem::{memmove, memset};
+use mem::memmove;
 
 // NOTE This function and the ones below are implemented using assembly because they using a custom
 // calling convention which can't be implemented using a normal Rust function
@@ -126,28 +126,11 @@ extern "C" {
     fn memset(dest: *mut u8, c: i32, n: usize) -> *mut u8;
 }
 
-// FIXME: The `*4` and `*8` variants should be defined as aliases.
-
-// Assembly optimized memclr{4,8} and memset{4,8}
-//
-// Original source: https://github.com/bobbl/libaeabi-cortexm0/blob/15e10736afed6f947fba4b5740274fec4f2c95ca/memset.S
-// Author: Jörg Mische <[email protected]>
-// License: ICS
-//
-// Copyright (c) 2013 Jörg Mische <[email protected]>
-//
-// Permission to use, copy, modify, and/or distribute this software for any
-// purpose with or without fee is hereby granted, provided that the above
-// copyright notice and this permission notice appear in all copies.
-//
-// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
-// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
-// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
-// OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+// Assembly optimized memclr{,4,8} and memset{,4,8}
 global_asm!(r"
+@ fn __aeabi_memclr(r0: *mut u8, r1: usize)
+    .global __aeabi_memclr
+
 @ fn __aeabi_memclr4(r0: *mut u8, r1: usize)
 @ r0 is 4-byte aligned
     .global __aeabi_memclr4
@@ -156,12 +139,9 @@ global_asm!(r"
 @ r0 is 8-byte aligned
     .global __aeabi_memclr8
 
-__aeabi_memclr4:
-__aeabi_memclr8:
-    @ r2 = r2 ^ r2 = 0
-    eors r2, r2
-
-    @ tail call __aeabi_memset4(r0, r1, 0)
+@ fn __aeabi_memset(r0: *mut u8, r1: usize, r2: i32)
+@ r0 is 4-byte aligned
+    .global __aeabi_memset
 
 @ fn __aeabi_memset4(r0: *mut u8, r1: usize, r2: i32)
 @ r0 is 4-byte aligned
@@ -171,42 +151,53 @@ __aeabi_memclr8:
 @ r0 is 8-byte aligned
     .global __aeabi_memset8
 
+__aeabi_memclr4:
+__aeabi_memclr8:
+    @ r2 = r2 ^ r2 = 0
+    eors r2, r2
+
+    @ tail call __aeabi_memset4(r0, r1, 0)
+
 __aeabi_memset4:
 __aeabi_memset8:
-    @ branch to '2' if r1 < 4
-    subs r1, #4
-    blo  2f
+    cmp r1, #4
+    blt __aeabi_memset
 
     @ copy r2 lower byte into all the other bytes of r2
-    @ e.g. r2 = 0xdead_beef -> r2 = 0xefef_efef
+    @ e.g. r2 = 0xdeadbeef -> r2 = 0xefefefef
     lsls r2, r2, #24
     lsrs r3, r2, #8
     orrs r2, r3
     lsrs r3, r2, #16
     orrs r2, r3
 
+    b    2f
+
 1:  @ word-wise copy loop
     str  r2, [r0]
     adds r0, #4
-    subs r1, #4
-    bhs  1b
+2:  subs r1, #4
+    bcc  1b
 
-2:  @ 3 bytes left to copy
-    @ r1 = (original_r1 % 4) - 4
+    adds r1, #4
+    b    __aeabi_memset
 
-    adds r1, #2       @ branch to '4' if (original_r1 % 4) == {0,1}
-    blo  4f
-    strb r2, [r0]
-    strb r2, [r0, #1]
-    beq  3f           @ branch to '3' if (original_r1 % 4) == 2
-    strb r2, [r0, #2]
-3:  bx   lr
+__aeabi_memclr:
+    @ r2 = r2 ^ r2 = 0
+    eors r2, r2
 
-4:  @ 1 byte left to copy
-    adds r1, #1
-    bne  5f           @ branch to '5' if (original_r1 % 4) == 0
-    strb r2, [r0]
-5:  bx   lr
+    @ tail call __aeabi_memset(r0, r1, 0)
+
+__aeabi_memset:
+    cmp r1, #0
+    beq 2f
+
+1:  strb r2, [r0]
+    adds r0, #1
+    subs r1, #1
+    bne  1b
+
+2:  bx lr
 "#);
 
 // Assembly optimized memcpy{,4,8}
@@ -252,6 +243,7 @@ __aeabi_memcpy:
 2:  bx   lr
 "#);
 
+// FIXME: The `*4` and `*8` variants should be defined as aliases.
 #[cfg_attr(not(test), no_mangle)]
 pub unsafe extern "aapcs" fn __aeabi_memmove(dest: *mut u8, src: *const u8, n: usize) {
     memmove(dest, src, n);
@@ -264,14 +256,3 @@ pub unsafe extern "aapcs" fn __aeabi_memmove4(dest: *mut u8, src: *const u8, n:
 pub unsafe extern "aapcs" fn __aeabi_memmove8(dest: *mut u8, src: *const u8, n: usize) {
     memmove(dest, src, n);
 }
-
-// Note the different argument order
-#[cfg_attr(not(test), no_mangle)]
-pub unsafe extern "aapcs" fn __aeabi_memset(dest: *mut u8, n: usize, c: i32) {
-    memset(dest, c, n);
-}
-
-#[cfg_attr(not(test), no_mangle)]
-pub unsafe extern "aapcs" fn __aeabi_memclr(dest: *mut u8, n: usize) {
-    memset(dest, 0, n);
-}