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Re: [PATCH, ARM] Fix out-of-range immediate assembly errors on 64-bit hosts

Hi Julian,

This patch fixes some immediate-out-of-range errors for VBIC, VORR etc. on 64-bit hosts. On such hosts, the X_add_number field of expressions will be 64 bits wide. INT_MIN and INT_MAX are used to signify that any immediate may be accepted for parse_immediate: unfortunately on a 64-bit host, 0xff000000 for instance is then interpreted as a positive integer outside that range.

Sorry - can you explain that last part again please ? I get how INT_MIN and INT_MAX are being used to indicate "any integer value is acceptable" to parse_immediate(), but where does this 0xffff0000 value come from and why would it cause problems for parse_immediate() ?

I've just made passing INT_MIN/INT_MAX disable the check instead, though I'm not very fond of that solution.

There appears to be only once place where INT_MAX/INT_MIN are used, so maybe it would be cleaner to change that code to pass realistic minimum and maximum values ?

    * config/tc-arm.c (parse_immediate): Handle 64-bit X_add_number

That sentence is not quite true. The change is to skip the range checks when the range is INT_MIN -> INT_MAX.

!       /* 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)
! 	{
!           inst.operands[i].reg = ((exp.X_add_number >> 16) >> 16) & 0xffffffff;
! 	  inst.operands[i].regisimm = 1;
! 	}

I am a little bit confused here. How is ((x >> 16) >> 16) different from (x >> 32) ? If not, then why express it that way ?


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