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GCC 4.1.2 for ARM (in NetBSD 4) produces buggy code with -fno-strict-aliasing?
Hi NetBSD ARMers,
I spent some time tracking down a panic for NetBSD/hpcarm 4.0 on a
Jornada 728, and I guess it is wise to share the result with this list.
Maybe this is already a well-known problem; I don't know.
The panic was triggered when I started using a wireless NIC. The crash
was in wi.o, and looking at the disassembly showed that GCC had produced
buggy code (it uses the wrong base register for loading a value).
c00d4018: e51b00d0 ldr r0, [fp, #-208]
c00d401c: e51b10d0 ldr r1, [fp, #-208]
c00d4020: e5900eb4 ldr r0, [r0, #3764]
c00d4024: e5903eb8 ldr r3, [r0, #3768]
The fourth line should not load using r0 as a base, but using r1.
By manually compiling wi.o and removing optimization options from the
command line, I noticed that removing -fno-strict-aliasing causes the
buggy code to be replaced with more reasonable code:
My guess is that all NetBSD ARM platforms which use this version of GCC
could be affected.
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