Deepak Bhole reports: When trying to build IcedTea with GCC 4.6, we encountered an error that stems from incorrect register allocation in release_store_fence(volatile jbyte* p, jbyte v) in orderAccess_linux_x86.inline.hpp. Specifically, the inline assembly call trying to do an atomic 8-bit exchange sets the output register constrain to r. The older versions GCC (by chance) ended up assigning the l-part of one of the a/b/c/d registers. However with 4.6, it attempts to do this with the %*bp register. This is fine on x86_64, but on i686 the bp register cannot be addressed in 8-bit (%bpl). This leads to a compilation failure: /builddir/build/BUILD/icedtea6-1.10/openjdk-ecj/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp: Assembler messages: /builddir/build/BUILD/icedtea6-1.10/openjdk-ecj/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp:160: Error: bad register name `%bpl' /builddir/build/BUILD/icedtea6-1.10/openjdk-ecj/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp:160: Error: bad register name `%bpl' It is possible to make it work on both 32 and 64-bit by constraining the output register further to only be one of a/b/c/d (=q). Though it was only that function that caused an error, I think it'd be best to change both uses of xchgb in orderAccess_linux_x86.inline.hpp to use =q. Here is the webrev for it: http://cr.openjdk.java.net/~dbhole/register-allocation-fix/webrev.00/ Christian Thalinger reports: I just stumbled over this same bug on one of our Ubuntu machines using GCC 4.5.1. What's the status of this fix? /home/twisti/hotspot-comp/7018355/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp: Assembler messages: /home/twisti/hotspot-comp/7018355/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp:160: Error: bad register name `%dil' /home/twisti/hotspot-comp/7018355/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp:160: Error: bad register name `%dil'
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