RFA: Patch for PR gas/12715 incorrect encoding of 64-bit immediates for ARM targets

[Matthew Gretton-Dann]

All,

PR gas/12715 shows a bug in gas when assembling 64-bit immediates on an
ARM target when gas has been configured for a 32-bit host, and with
support multiple targets at least one of which is a 64-bit target.

The issue is here in gas/config/tc-arm.c, parse_big_immediate:

      /* If we're on a 64-bit host, then a 64-bit number can be returned
using
        O_constant.  We have to be careful not to break compilation for
        32-bit X_add_number, though.  */
      if ((exp.X_add_number & ~0xffffffffl) != 0)
        ...

On a 32-bit host with a 64-bit target exp.X_add_number is (ultimately)
of type BFD_HOST_64_BIT.  In this parser has stored the whole 64-bit
immediate in exp.X_add_number - not (as in the case when on a 32-bit
host with a 32-bit target) as a bignum.

In this case the if test above always fails, as 0xffffffffl is treated
as a 32-bit integer, so the bitwise inverse is 0, and so the test can
never be true.  And so the 64-bit immediate gets its top 32-bits set to
zero.

The fix is to make sure the constant is of the correct type before doing
the bitwise inverse.

I have tested this on an x86-64 host with the following configuration 
options:
 * --target=arm-none-eabi
 * --target=arm-none-eabi --enable-targets=all
 * --target=arm-none-eabi CFLAGS=-m32
 * --target=arm-none-eabi --enable-targets=all CFLAGS=-m32

Is this okay for trunk and the 2.21 branch?

Thanks,

Matt

gas/ChangeLog:
2011-05-11  Matthew Gretton-Dann  <matthew.gretton-dann@arm.com>

	PR gas/12715
	* config/tc-arm.c (parse_big_immediate):  Fix parsing of 64-bit
	immediates on 32-bit hosts.

gas/testsuite/ChangeLog:
2011-05-11  Matthew Gretton-Dann  <matthew.gretton-dann@arm.com>

	PR gas/12715
	* gas/arm/neon-const.s: Add testcase for 64-bit Neon constants.
	* gas/arm/neon-const.d: Likewise.

-- 
Matthew Gretton-Dann
Principal Engineer - PDSW Tools
ARM Ltd
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