Unsupported ARM mrc encodings

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Bugzilla Link	20533
Resolution	FIXED
Resolved on	Jun 16, 2016 07:47
Version	trunk
OS	Linux
Blocks	#19300
CC	@rengolin

Extended Description

The llvm assembler doesnt support some special encodings which exist atleast for Arm9:

mrc p15, 0, r15, c7, c14, 3
mrc p15, 0, r15, c7, c10, 3

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0290g/Babebdcb.html

Tested using Clang 3.5 from the Wheezy repository:
Debian clang version 3.5.0-1~exp1 (trunk) (based on LLVM 3.5.0)

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Posted wrong link, correct link is:
http://infocenter.arm.com/help/topic/com.arm.doc.ddi0198e/I1014942.html#Cegbgjhf

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Compiler commandline is:
arm-none-eabi-clang++ -fmessage-length=0 -mcpu=arm926ej-s -fstrict-aliasing -fstrict-overflow -Wpointer-arith -std=gnu++11 -Wall -Wstrict-overflow=3 -O0 -g3 -gdwarf-4 -fasynchronous-unwind-tables

some more invalid operands:
MRC P15, 0, R0, C3, c0, 0
MCR P15, 0, R0, C3, c0, 0

unknown token in expression (usefull pseudo op in gas and arm assembler):
ldr r0, =#-0x408

unknown directive:
.sect

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Hexadecimal Numbers seem to be unsupported if they start with 0X (upper case X)
eg.

.skip 0x64
.skip 0X64 /* Error !/
mov r0, #​0x64
mov r0, #​0X64 / Error !*/

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Hello?

This doesnt seem a big problem to fix

[rengolin]

A bit late to see this, but most of the problems have been fixed.

1. MRC/MCR and friends have been implemented

• Your example uses r15 which is not allowed
• Clang catches it, GAS doesn't

2. ldr r0, = has been implemented (will be available in 3.9)

• With the exception that it doesn't use the # syntax (GAS accepts it, too)

Others, not yet:

3. The assembler is still case sensitive

• We may want to fix that... on another bug

4. .sect doesn't seem to be implemented

• We may want to fix that... on another bug

Since this bug was originally for MRC/MCR, I'm closing it.

If you want the other two issues looked at, please open one bug each and show what is the case for supporting them, other than "GAS accepts it", as GAS accepts many things that are wrong and we shouldn't just do the same.