sysdeps/i386/i586/strcpy.S has andl $3, %ecx #ifdef PIC call 2f cfi_adjust_cfa_offset (4) 2: popl %edx cfi_adjust_cfa_offset (-4) /* 0xb is the distance between 2: and 1: but we avoid writing 1f-2b because the assembler generates worse code. */ leal 0xb(%edx,%ecx,8), %ecx #else leal 1f(,%ecx,8), %ecx #endif jmp *%ecx .align 8 1: orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi L(1): movl (%esi), %ecx leal 4(%esi),%esi Change a single instruction will break the jump table.
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, hjl/pr22353/master has been created at 5ed1b97d3112ce0f5d3cf57e7e50d6b1481740be (commit) - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=5ed1b97d3112ce0f5d3cf57e7e50d6b1481740be commit 5ed1b97d3112ce0f5d3cf57e7e50d6b1481740be Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 06:31:57 2017 -0700 Add strcpy-stosb.S https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=cc4474bf8263e6621dff29a12d8a5ddd39ec800e commit cc4474bf8263e6621dff29a12d8a5ddd39ec800e Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 03:09:12 2017 -0700 Add i386 strcpy.S https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b44640054b78c21bf3176dd0e82c4c8f5c2b758c commit b44640054b78c21bf3176dd0e82c4c8f5c2b758c Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 02:31:13 2017 -0700 i586: Use a jump table in strcpy.S {BZ #22353] i586 strcpy.S used a clever trick with LEA to avoid jump table: /* ECX has the last 2 bits of the address of source - 1. */ andl $3, %ecx call 2f 2: popl %edx /* 0xb is the distance between 2: and 1:. */ leal 0xb(%edx,%ecx,8), %ecx jmp *%ecx .align 8 1: /* ECX == 0 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 1 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 2 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 3 */ L(1): movl (%esi), %ecx leal 4(%esi),%esi This may fail if there are instruction changes before L(1):. This patch replaces it with a jump table which works with any instruction changes. Tested on i586 and i686 with and without --disable-multi-arch. {BZ #22353] * sysdeps/i386/i586/strcpy.S (JMPTBL): New. (BRANCH_TO_JMPTBL_ENTRY): Likewise. (STRCPY): Use it. (1): Renamed to ... (L(Src0)): This. (L(Src1)): New. (L(Src2)): Likewise. (L(1)): Renamed to ... (L(Src3)): This. (L(SrcTable)): New. -----------------------------------------------------------------------
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, hjl/pr22353/master has been created at 75588c0e4cd27ad868256d094b5f7646bc404ca8 (commit) - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=75588c0e4cd27ad868256d094b5f7646bc404ca8 commit 75588c0e4cd27ad868256d094b5f7646bc404ca8 Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 06:31:57 2017 -0700 Add strcpy-stosb.S https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2fa584ae979326fd9cb33e6df9c50976643cbd84 commit 2fa584ae979326fd9cb33e6df9c50976643cbd84 Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 03:09:12 2017 -0700 Add i386 strcpy.S https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d78abd26b8c8da5b9d67773343824606f9c96a6a commit d78abd26b8c8da5b9d67773343824606f9c96a6a Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 02:31:13 2017 -0700 i586: Use a jump table in strcpy.S [BZ #22353] i586 strcpy.S used a clever trick with LEA to avoid jump table: /* ECX has the last 2 bits of the address of source - 1. */ andl $3, %ecx call 2f 2: popl %edx /* 0xb is the distance between 2: and 1:. */ leal 0xb(%edx,%ecx,8), %ecx jmp *%ecx .align 8 1: /* ECX == 0 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 1 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 2 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 3 */ L(1): movl (%esi), %ecx leal 4(%esi),%esi This may fail if there are instruction changes before L(1):. This patch replaces it with a jump table which works with any instruction changes. Tested on i586 and i686 with and without --disable-multi-arch. [BZ #22353] * sysdeps/i386/i586/strcpy.S (JMPTBL): New. (BRANCH_TO_JMPTBL_ENTRY): Likewise. (STRCPY): Use it. (1): Renamed to ... (L(Src0)): This. (L(Src1)): New. (L(Src2)): Likewise. (L(1)): Renamed to ... (L(Src3)): This. (L(SrcTable)): New. -----------------------------------------------------------------------
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, hjl/pr22353/master has been created at 610a04b517cadd2a461515ffa8da77b42ccb596e (commit) - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=610a04b517cadd2a461515ffa8da77b42ccb596e commit 610a04b517cadd2a461515ffa8da77b42ccb596e Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 06:31:57 2017 -0700 Add strcpy-stosb.S https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9b733b73b096a7c2f685c427d89431444603ac9f commit 9b733b73b096a7c2f685c427d89431444603ac9f Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 03:09:12 2017 -0700 Add i386 strcpy.S https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9a89973274f901f4c3313e6e2b84d6b2108c7924 commit 9a89973274f901f4c3313e6e2b84d6b2108c7924 Author: H.J. Lu <hjl.tools@gmail.com> Date: Fri Oct 27 02:31:13 2017 -0700 i586: Use a jump table in strcpy.S [BZ #22353] i586 strcpy.S used a clever trick with LEA to avoid jump table: /* ECX has the last 2 bits of the address of source - 1. */ andl $3, %ecx call 2f 2: popl %edx /* 0xb is the distance between 2: and 1:. */ leal 0xb(%edx,%ecx,8), %ecx jmp *%ecx .align 8 1: /* ECX == 0 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 1 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 2 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 3 */ L(1): movl (%esi), %ecx leal 4(%esi),%esi This may fail if there are instruction length changes before L(1):. This patch replaces it with a jump table which works with any instruction length changes. Tested on i586 and i686 with and without --disable-multi-arch. [BZ #22353] * sysdeps/i386/i586/strcpy.S (JMPTBL): New. (BRANCH_TO_JMPTBL_ENTRY): Likewise. (STRCPY): Use it. (1): Renamed to ... (L(Src0)): This. (L(Src1)): New. (L(Src2)): Likewise. (L(1)): Renamed to ... (L(Src3)): This. (L(SrcTable)): New. -----------------------------------------------------------------------
This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GNU C Library master sources". The branch, master has been updated via c5cc45148c89cc5c57d1946348dd242d4db5c5f5 (commit) from ce12269fac8cb873df1a8785e4a6cde870855590 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c5cc45148c89cc5c57d1946348dd242d4db5c5f5 commit c5cc45148c89cc5c57d1946348dd242d4db5c5f5 Author: H.J. Lu <hjl.tools@gmail.com> Date: Mon Oct 30 10:02:16 2017 -0700 i586: Use conditional branches in strcpy.S [BZ #22353] i586 strcpy.S used a clever trick with LEA to implement jump table: /* ECX has the last 2 bits of the address of source - 1. */ andl $3, %ecx call 2f 2: popl %edx /* 0xb is the distance between 2: and 1:. */ leal 0xb(%edx,%ecx,8), %ecx jmp *%ecx .align 8 1: /* ECX == 0 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 1 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 2 */ orb (%esi), %al jz L(end) stosb xorl %eax, %eax incl %esi /* ECX == 3 */ L(1): movl (%esi), %ecx leal 4(%esi),%esi This fails if there are instruction length changes before L(1):. This patch replaces it with conditional branches: cmpb $2, %cl je L(Src2) ja L(Src3) cmpb $1, %cl je L(Src1) L(Src0): which have similar performance and work with any instruction lengths. Tested on i586 and i686 with and without --disable-multi-arch. [BZ #22353] * sysdeps/i386/i586/strcpy.S (STRCPY): Use conditional branches. (1): Renamed to ... (L(Src0)): This. (L(Src1)): New. (L(Src2)): Likewise. (L(1)): Renamed to ... (L(Src3)): This. ----------------------------------------------------------------------- Summary of changes: ChangeLog | 11 +++++++++++ sysdeps/i386/i586/strcpy.S | 28 +++++++++++----------------- 2 files changed, 22 insertions(+), 17 deletions(-)
Fixed for 2.27.