[Bug middle-end/50569] Wrong code error: memcpy eliminated when it is needed

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50569

Mikael Pettersson <mikpe at it dot uu.se> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jamborm at gcc dot gnu.org

--- Comment #8 from Mikael Pettersson <mikpe at it dot uu.se> 2011-11-04 20:57:51 UTC ---
The regression started with r164136:
http://gcc.gnu.org/ml/gcc-cvs/2010-09/msg00428.html

Comparing the ARM assembly code from r164135 and r164136 on the reduced test
case clearly shows the error:

--- pr50569.s-r164135   2011-11-04 21:06:58.000000000 +0100
+++ pr50569.s-r164136   2011-11-04 21:10:48.000000000 +0100
@@ -17,19 +17,10 @@
        @ args = 0, pretend = 0, frame = 0
        @ frame_needed = 0, uses_anonymous_args = 0
        @ link register save eliminated.
-       ldrb    r2, [r0, #1]    @ zero_extendqisi2
-       ldrb    r3, [r0, #0]    @ zero_extendqisi2
-       ldrb    r1, [r0, #2]    @ zero_extendqisi2
-       orr     r3, r3, r2, asl #8
-       ldrb    r2, [r0, #3]    @ zero_extendqisi2
-       orr     r3, r3, r1, asl #16
-       orr     r3, r3, r2, asl #24
+       ldr     r3, [r0, #0]
        cmp     r3, #63
        mvnls   r3, #0
-       strlsb  r3, [r0, #0]
-       strlsb  r3, [r0, #1]
-       strlsb  r3, [r0, #2]
-       strlsb  r3, [r0, #3]
+       strls   r3, [r0, #0]
        bx      lr
        .size   frob_entry, .-frob_entry
        .align  2