[llvm-commits] [llvm] r141365 - in /llvm/trunk: lib/Target/ARM/ARMISelDAGToDAG.cpp lib/Target/ARM/ARMISelLowering.cpp lib/Target/ARM/ARMInstrInfo.td lib/Target/ARM/ARMInstrThumb2.td test/CodeGen/ARM/iabs.ll test/CodeGen/Thumb/iabs.ll

[Ana Pazos]

Folks,

I tried to find the ARM Architecture Reference Manual for ARMv6 from ARM website. It is not available anymore according to this FAQ:

"The original ARM v6 Architecture Reference Manual for the ARM11 cores (ARM DDI 0100I) is superseded by the ARMv7-AR Architecture Reference Manual which is now the definitive document for Applications and Real-Time variants of the v6 and v7 ARM Architecture, including all ARM11-class cores."
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka6657.html


But the Architecture Reference Manual for ARMv7A and ARMV7AR (ARM DDI 0406B) page A8-285 says this about RSB immediate instruction:

"The immediate value to be added to the value obtained from <Rn>. The only permitted value for encoding T1 is 0. See Modified immediate constants in Thumb instructions on page A6-17 or Modified immediate constants in ARM instructions on page A5-9 for the range of values for encoding T2 or A1".
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0406b/index.html


So it should be ok to encode rsb with immediate value 0 in Thumb1 mode... Not sure why the assembler complains:

arm-none-linux-gnueabi-gcc -march=armv6 floatsidf.s -o floatsidf.o
floatsidf.s: Assembler messages:
floatsidf.s:2: Error: character following name is not '#'
floatsidf.s:3: Error: unknown pseudo-op: `.private_extern'
floatsidf.s:7: Error: junk at end of line, first unrecognized character is`_'
floatsidf.s:19: Error: cannot honor width suffix -- `rsb r0,r0,#0'
floatsidf.s:100: Error: unknown pseudo-op: `.subsections_via_symbols'

Anyways, attached is the patch to disable the optimization in Thumb1 mode.

Thanks,
Ana.

-----Original Message-----
From: Anton Korobeynikov [mailto:anton at korobeynikov.info] 
Sent: Friday, October 07, 2011 2:58 PM
To: Ana Pazos
Cc: Eric Christopher; llvm-commits at cs.uiuc.edu; rajav at codeaurora.org
Subject: Re: [llvm-commits] [llvm] r141365 - in /llvm/trunk: lib/Target/ARM/ARMISelDAGToDAG.cpp lib/Target/ARM/ARMISelLowering.cpp lib/Target/ARM/ARMInstrInfo.td lib/Target/ARM/ARMInstrThumb2.td test/CodeGen/ARM/iabs.ll test/CodeGen/Thumb/iabs.ll

Hi Ana,

> What is your command line? Did you set any other flags?
Attached is .ll and .s.
For me it seems we should just disable this transform in Thumb1 mode.
What do you think?

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University
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