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# commit 0b2c2ace3601d5d59cf89130b16840e7f132f7a6
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# Author: Alan Modra <amodra@gmail.com>
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# Date: Sat Aug 17 18:36:45 2013 +0930
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#
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# PowerPC makecontext
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# http://sourceware.org/ml/libc-alpha/2013-08/msg00092.html
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#
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# Use conditional form of branch and link to avoid destroying the cpu
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# link stack used to predict blr return addresses.
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#
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# * sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S: Use
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# conditional form of branch and link when obtaining pc.
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# * sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S: Likewise.
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#
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diff -urN glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S
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--- glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S 2014-05-28 12:25:49.000000000 -0500
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+++ glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc32/makecontext.S 2014-05-28 12:25:51.000000000 -0500
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@@ -47,7 +47,9 @@
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#ifdef PIC
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mflr r0
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cfi_register(lr,r0)
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- bl 1f
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+ /* Use this conditional form of branch and link to avoid destroying
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+ the cpu link stack used to predict blr return addresses. */
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+ bcl 20,31,1f
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1: mflr r6
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addi r6,r6,L(exitcode)-1b
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mtlr r0
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@@ -136,7 +138,9 @@
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#ifdef PIC
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mflr r0
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cfi_register(lr,r0)
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- bl 1f
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+ /* Use this conditional form of branch and link to avoid destroying
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+ the cpu link stack used to predict blr return addresses. */
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+ bcl 20,31,1f
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1: mflr r6
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addi r6,r6,L(novec_exitcode)-1b
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mtlr r0
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diff -urN glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
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--- glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S 2014-05-28 12:25:49.000000000 -0500
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+++ glibc-2.17-c758a686/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S 2014-05-28 12:25:51.000000000 -0500
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@@ -124,8 +124,10 @@
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/* If the target function returns we need to do some cleanup. We use a
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code trick to get the address of our cleanup function into the link
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- register. Do not add any code between here and L(exitcode). */
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- bl L(gotexitcodeaddr);
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+ register. Do not add any code between here and L(exitcode).
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+ Use this conditional form of branch and link to avoid destroying
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+ the cpu link stack used to predict blr return addresses. */
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+ bcl 20,31,L(gotexitcodeaddr);
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/* This is the helper code which gets called if a function which
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is registered with 'makecontext' returns. In this case we
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