[Bug c/13984] New: Bad code generated with -O0

["klawson at ad-holdings dot co dot uk" <gcc-bugzilla at gcc dot gnu dot org>]

The following code was generated by sh-elf-gcc. The space variable (a long) is
taken from @(0,r3) and stored in r1. The len variable is taken from @(4.r3) and
stored in r3. A subtract operation is then performed, and r3 is used to find
where to store the result. This is bad because r3 was used as temporary storage
for the subtract operation and no longer contains a reference to memory. The
final mov.l instruction causes a fault as it is storing to a misaligned
(nonsense) address.

	576				space -= len;
-	0x8c0bb984	<cyg_sosend+2148>:		mov	#64,r3
-	0x8c0bb986	<cyg_sosend+2150>:		add	r14,r3
-	0x8c0bb988	<cyg_sosend+2152>:		mov	#64,r3
-	0x8c0bb98a	<cyg_sosend+2154>:		add	r14,r3
-	0x8c0bb98c	<cyg_sosend+2156>:		mov.l	@(0,r3),r1
-	0x8c0bb98e	<cyg_sosend+2158>:		mov.l	@(4,r3),r3
-	0x8c0bb990	<cyg_sosend+2160>:		sub	r3,r1
-	0x8c0bb992	<cyg_sosend+2162>:		mov.l	r1,@(0,r3)

The following CFLAGS are used:
-mb -m3 -Wall -Wpointer-arith -Wstrict-prototypes -Winline -Wundef
-Woverloaded-virtual -ggdb -O0 -ffunction-sections -fdata-sections -fno-rtti
-fno-exceptions -fvtable-gc -finit-priority

Using optimisation level 1, the code is generated as:
	576				space -= len;
-	0x8c0a6080	<cyg_sosend+1280>:		sub	r8,r11

-- 
           Summary: Bad code generated with -O0
           Product: gcc
           Version: 3.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: klawson at ad-holdings dot co dot uk
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-cygwin
GCC target triplet: sh-elf-gcc


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13984