I check the current implementation of browser and vfrcompile, detail shows
below:
Below IFR data generated from the vfr file:
suppressif 8|8 == 0x8;
>000001AA: 0A 82
>000001AC: 45 8A 08 00 00 00 00 00 00 00
>000001B6: 45 0A 08 00 00 00 00 00 00 00
>000001C0: 45 0A 08 00 00 00 00 00 00 00
>000001CA: 2F 02
>000001CC: 36 02
>000001CE: 29 02
checkbox varid = MyIfrNVData.ChooseToActivateNuclearWeaponry,
>000001D0: 06 8E 29 00 2A 00 03 00 34 12 D4 00 00 03
prompt = STRING_TOKEN(0x0029),
help = STRING_TOKEN(0x002A),
flags = CHECKBOX_DEFAULT | CHECKBOX_DEFAULT_MFG,
default = TRUE,
>000001DE: 5B 06 00 00 00 01
endcheckbox;
>000001E4: 29 02
endif;
>000001E6: 29 02
In browser, when do the "|" operate, it save the result as an UINT64 type and
the result is 0x9. When check the suppressif opcode, it found the data type is
UINT64 and value is 0x9,not 0, so the checkbox is suppressed.
Thanks,
Eric
-----Original Message-----
From: Tim Lewis [mailto:tim.le...@insyde.com]
Sent: Friday, August 29, 2014 7:18 AM
To: edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] Bitwise OR operator problems
So this leads to the follow on question (now that I've got the precedence
straight): suppressif 8|8 == 0x8 is an illegal statement.
in IFR (8 8 EFI_IFR_EQUAL 8 EFI_IFR_BITWISE_OR) since EFI_IFR_EQUAL results in
a BOOLEAN, but EFI_IFR_BITWISE_OR requires an integer, and IFR is strongly
typed.
In Laszlo's original analysis: 8|(8 == 0x8) means 8|1
The specification says:
This opcode performs the following actions:
1. Pop two expressions from the expression stack.
2. If the two expressions cannot be evaluated as unsigned integers, push
Undefined.
3. Otherwise, zero-extend the unsigned integers to 64-bits.
4. Perform a bitwise-OR of the two values.
5. Push the result.
There is no implicit type conversion in IFR, so in order for VfrCompile.exe to
handle this expression, I would expect a EFI_IFR_TO_BOOLEAN to be generated
implicitly. But in my analysis of the IFR being generated, it is not.
In fact, an optimizer tool we have written catches these as errors, along with
the fact that the suppressif expression is not evaluating to a bool.
Tim
-----Original Message-----
From: Tim Lewis [mailto:tim.le...@insyde.com]
Sent: Thursday, August 28, 2014 5:53 PM
To: edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] Bitwise OR operator problems
Laszlo --
You are correct. I have verified the VFR grammar which has similar priority.
It is actually the behavior for integer conversion in suppressif that is
confusing me, not the order of evaluation like I thought.
Tim
-----Original Message-----
From: Laszlo Ersek [mailto:ler...@redhat.com]
Sent: Thursday, August 28, 2014 5:43 PM
To: edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] Bitwise OR operator problems
On 08/28/14 11:31, Laszlo Ersek wrote:
> In the C language, both operator & and operator | bind
> *less* strongly than operator ==.
(Sorry for following up on my own email.) I found some references:
http://en.wikipedia.org/wiki/Operator_precedence_in_C#Criticism_of_bitwise_and_equality_operators_precedence
http://cm.bell-labs.com/cm/cs/who/dmr/chist.html
See under "Neonatal C".
Thanks
Laszlo
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