linaro-toolchain February 2011

linaro-toolchain@lists.linaro.org

27 participants
66 discussions

by Ira Rosen

Hi, I continued to work on vect_interleave and vect_extract implementation on NEON: * debugged the compiler to find out what's the problem with neon_vzip/vuzp<mode>_internal * fixed it following Uli's advice * checked how neon_vzip/vuzp<mode>_internal work for intrinsics by writing tests * fixed the patch according to Uli's comments * now fully testing the patch Thanks, Ira

13 years, 9 months

Help with define_insn

by Ira Rosen

Hi, I am trying to implement interleave_high/low and extract_even/odd using vzip and vuzp instructions. I am attaching a patch that attempts to do that. It uses already existing neon_vzip<mode>_internal. The problem with it is that it doesn't express the fact that the two outputs of vzip depend on both inputs, which causes wrong code generation in CSE: for (a,b)<- vzip (c,d) and (e,f) <- vzip (g,d) CSE decides that b==f, since on RTL level b and f depend only on d. Here is neon_vzip<mode>_internal: (define_insn "neon_vzip<mode>_internal" [(set (match_operand:VDQW 0 "s_register_operand" "=w") (unspec:VDQW [(match_operand:VDQW 1 "s_register_operand" "0")] UNSPEC_VZIP1)) (set (match_operand:VDQW 2 "s_register_operand" "=w") (unspec:VDQW [(match_operand:VDQW 3 "s_register_operand" "2")] UNSPEC_VZIP2))] "TARGET_NEON" "vzip.<V_sz_elem>\t%<V_reg>0, %<V_reg>2" [(set (attr "neon_type") (if_then_else (ne (symbol_ref "<Is_d_reg>") (const_int 0)) (const_string "neon_bp_simple") (const_string "neon_bp_3cycle")))] ) Is there a way to properly mark the dependence? Thanks, Ira

13 years, 9 months

qemu-linaro prerelease available

by Peter Maydell

Hi; this is a note to say that we have now produced a prerelease tarball of qemu-linaro. (The first formal qemu-linaro release will happen in sync with other toolchain group releases on 8th Feb.) This prerelease is primarily to pipeclean the release process and to allow work to start on producing Ubuntu and Linaro packages; however it does include a number of useful bugfixes which are required if you want to be able to boot a recent Linaro snapshot on the beagle model. So the enthusiastic might like to build it from source and give it a spin. Like the Linaro kernel trees, the qemu-linaro tree aims to only include patches we are confident will go upstream; at the moment this means the OMAP3 support and ARM correctness fixes from the qemu-meego tree, based on the qemu upstream trunk. You can download the source tarball from: https://launchpad.net/qemu-linaro/+milestone/2011.02 -- Peter Maydell

13 years, 9 months

IT block semantic question

by David Gilbert

Hi, What do people understand to be the expected semantics of IT blocks in the cases below, of which there has been some confusion in relation to a recent Qt issue. The code in question had a sequence something like: comparison IT... EQ blahEQ TEQ BEQ The important bits here are that we have an IT EQ block and two special cases: 1) There is a TEQ in the IT block - are all comparisons in the block allowed and do their effects immediately take effect? As far as I can tell this is allowed and any flag changes are used straight away; 2) There is a BEQ at the end of the IT block, as far as I can tell, as long as the destination of the BEQ is close it shouldn't make any difference if the BEQ is included in the IT block or not. Does that match everyone elses understanding? Dave

13 years, 9 months

Generating ancilliary sections with gas

by Dave Martin

Hi all, With gas, does anyone know of a way to create a section whose name is based on that of the current section? The specific requirement is to be able to define a generic macro like the example "fixup" below, whose purpose is to record ancilliary data related to some other section. To illustrate: .macro fixup 100\@ : .pushsection fixup<current section name>, "a" .long 100\@b .popsection .endm .text ... fixup .long sym1 ... .section .other, "ax" ... fixup .long sym2 The linux kernel uses a technique just like this for patching SMP kernels at bootup to work on uniprocessor platforms (when CONFIG_SMP_ON_UP is enabled), resulting in code looking something like this: void exit __attribute__ (( __section__ (".text.exit") )) { ... asm( ... FIXUP("something") ... ); } Note that the inline asm may actually come out of a generic header file rather than being explitly written for this invocation. So it may have to be truly generic. Is far as I have been able to determine, it's not possible to generate sections named based on the current section. In practice, the kernel puts all the fixups into a single section. The downside of this is that when sections are selectively discarded at link time (which in general may happen -- for example, Linux discards the "module exit" code for drivers which are built into the kernel and therefore never exit) there is no way to selectively discard the related fixup entries. Currently the only solution is to include all the module exit code in the image and discard it at run-time when the kernel boots. This is obviously wasteful. Attempting to discard that code at like time results in a link error, since fixups refer to the removed sections. Of course, the "fixup" macro could be given an extra parameter to name the containing section, but the macro can then no longer be called in a generic way: all the calls to that macro must be manually (and buggily) maintained to ensure that the referenced section name is correct, some object post-processing must be done before linking, and/or a tool must be created to implement the missing assembler functionality. Unfortunately, such solutions are likely to be too fragile or complex to make it upstream. It's interesting to note that the same problem will apply for any section containing ancilliary data for another section. In particular, it looks like either the ABI or the assembler has had to grow a special-case workaround for this in order to support exception unwind information sections generated by .fnstart ... .fnend in a sane way: the unwind information sections get called .ARM.ex{idx,tab} for .text, and .ARM.ex{idx,tab}<section> for any other section. As a consequence, link-time discarding can handle this information properly, but IMHO this is a bit of a cheat and admits the general need to create sections with names based transparently on those of other sections, without satisfying that need. .popsection is also an example of such a cheat: most other aspects of assmbler state still cannot be saved and restored. In general, it would be useful if gas supported some general reflective abilities: i.e., the ability to query the current assembler state (section, subsection, active instruction set, active macro mode, etc.) and/or the ability to wrap or hook existing pseudo-ops. For example, the above problem would almost certainly solvable using assembler macros (albeit painfully) if wrapper macros could be defined for the section manipulation directives (section, .text, .data, .bss, .pushsection, .popsection, .previous). However, supporting some magic macro parameters reflecting the assembler state would be a lot simpler. As an example of the kind of behaviour I think would be useful, the macro argument qualifier could be extended to allow macros to query the assembler state in a backwards-compatible way; something like: .macro fixup base_section:gas_current_section_name, old_altmacro:gas_macro_mode .altmacro LOCAL fixup_location fixup_location: .pushsection \base_section\().fixup .long 100\@b .popsection \old_altmacro .endm Existing assembler code will continue to work just fine with this approach. Note how this also enables a local label to be generated hygenically, by making it possible to save and restore the macro mode. Otherwise, .altmacro (and hence LOCAL) is hard to use safely, since the initial macro mode is unknown and can't be restored. Any thoughts / comments? Cheers. ---Dave

13 years, 9 months

[GCC 5.5 - Help on ERROR] Compilation fails with mfpu=neon

by ShankarGanesh Kandasamy

Hi, Following compilation fails with -O3 -mfpu=neon,(but successful on -O2, -mfpu=neon) for Cortex-A5. Could you please help me out to resolve this error ? ubuntu@tegra:~/$ gcc-4.5 -v -c -o utility.o -DLINUX -DUNIX -DHAS_LONGLONG -DLITTLE_ENDIAN_ARCH -DSPEC_CPU2000 -O3 -mcpu=cortex-a5 -marm -mfpu=neon -mfloat-abi=softfp utility.c Using built-in specs. COLLECT_GCC=gcc-4.5 COLLECT_LTO_WRAPPER=/usr/lib/gcc/arm-linux-gnueabi/4.5.1/lto-wrapper Target: arm-linux-gnueabi Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.5.1-7ubuntu2' --with-bugurl=file:///usr/share/doc/gcc-4.5/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.5 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.5 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-plugin --enable-objc-gc --disable-sjlj-exceptions --with-arch=armv7-a --with-float=softfp --with-fpu=vfpv3-d16 --with-mode=thumb --disable-werror --enable-checking=release --build=arm-linux-gnueabi --host=arm-linux-gnueabi --target=arm-linux-gnueabi Thread model: posix gcc version 4.5.1 (Ubuntu/Linaro 4.5.1-7ubuntu2) COLLECT_GCC_OPTIONS='-v' '-c' '-o' 'utility.o' '-DLINUX' '-DUNIX' '-DHAS_LONGLONG' '-DLITTLE_ENDIAN_ARCH' '-DSPEC_CPU2000' '-O3' '-mcpu=cortex-a5' '-marm' '-mfpu=neon' '-mfloat-abi=softfp' /usr/lib/gcc/arm-linux-gnueabi/4.5.1/cc1 -quiet -v -DLINUX -DUNIX -DHAS_LONGLONG -DLITTLE_ENDIAN_ARCH -DSPEC_CPU2000 utility.c -D_FORTIFY_SOURCE=2 -quiet -dumpbase utility.c -mcpu=cortex-a5 -marm -mfpu=neon -mfloat-abi=softfp -auxbase-strip utility.o -O3 -version -fstack-protector -o /tmp/ccaZnpsw.s GNU C (Ubuntu/Linaro 4.5.1-7ubuntu2) version 4.5.1 (arm-linux-gnueabi) compiled by GNU C version 4.5.1, GMP version 4.3.2, MPFR version 3.0.0-p3, MPC version 0.8.2 GGC heuristics: --param ggc-min-expand=64 --param ggc-min-heapsize=64482 ignoring nonexistent directory "/usr/local/include/arm-linux-gnueabi" ignoring nonexistent directory "/usr/lib/gcc/arm-linux-gnueabi/4.5.1/../../../../arm-linux-gnueabi/include" ignoring nonexistent directory "/usr/include/arm-linux-gnueabi" #include "..." search starts here: #include <...> search starts here: /usr/local/include /usr/lib/gcc/arm-linux-gnueabi/4.5.1/include /usr/lib/gcc/arm-linux-gnueabi/4.5.1/include-fixed /usr/include End of search list. GNU C (Ubuntu/Linaro 4.5.1-7ubuntu2) version 4.5.1 (arm-linux-gnueabi) compiled by GNU C version 4.5.1, GMP version 4.3.2, MPFR version 3.0.0-p3, MPC version 0.8.2 GGC heuristics: --param ggc-min-expand=64 --param ggc-min-heapsize=64482 Compiler executable checksum: 52c4962735600b49ca41dc70631edd04 COLLECT_GCC_OPTIONS='-v' '-c' '-o' 'utility.o' '-DLINUX' '-DUNIX' '-DHAS_LONGLONG' '-DLITTLE_ENDIAN_ARCH' '-DSPEC_CPU2000' '-O3' '-mcpu=cortex-a5' '-marm' '-mfpu=neon' '-mfloat-abi=softfp' as -mcpu=cortex-a5 -mfloat-abi=softfp -mfpu=neon -meabi=5 -o utility.o /tmp/ccaZnpsw.s /tmp/ccaZnpsw.s: Assembler messages: /tmp/ccaZnpsw.s:460: Error: VFP/Neon double precision register expected -- `vmovl.s16 q5,s20' /tmp/ccaZnpsw.s:531: Error: VFP/Neon double precision register expected -- `vmovl.s16 q9,s14' /tmp/ccaZnpsw.s:537: Error: VFP/Neon double precision register expected -- `vmovl.s16 q7,s28' /tmp/ccaZnpsw.s:542: Error: VFP/Neon double precision register expected -- `vmovl.s16 q13,s12' /tmp/ccaZnpsw.s:543: Error: VFP/Neon double precision register expected -- `vmovl.s16 q14,s10' /tmp/ccaZnpsw.s:544: Error: VFP/Neon double precision register expected -- `vmovl.s16 q3,s8' /tmp/ccaZnpsw.s:546: Error: VFP/Neon double precision register expected -- `vmovl.s16 q2,s6' /tmp/ccaZnpsw.s:549: Error: VFP/Neon double precision register expected -- `vmovl.s16 q1,s4' /tmp/ccaZnpsw.s:550: Error: VFP/Neon double precision register expected -- `vmovl.s16 q0,s0' /tmp/ccaZnpsw.s:551: Error: VFP/Neon double precision register expected -- `vmovl.s16 q4,s16' Regards, Shankar -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.

13 years, 9 months

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linaro-toolchain February 2011