s390: optimize syscall function

Since kernel 2.6.0 all Linux version accept the system call number
in register 1 for svc 0. There is no need to have special handling
that uses EX for system calls < 256. This will simplify and speed
up that code.

A microbenchmark doing "syscall(__NR_getpid);" in a loops gets faster
by ~12%.

        * sysdeps/unix/sysv/linux/s390/s390-32/syscall.S: Simplify
        code by always using SVC 0 instead of EX.
        * sysdeps/unix/sysv/linux/s390/s390-64/syscall.S: Likewise.

diff --git a/ChangeLog b/ChangeLog
index f4ac921..bf6c25a 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-06-19  Christian Borntraeger  <borntraeger@de.ibm.com>
+
+       * sysdeps/unix/sysv/linux/s390/s390-32/syscall.S (syscall):
+       Simplify code by always using SVC 0 instead of EX.
+       * sysdeps/unix/sysv/linux/s390/s390-64/syscall.S: Likewise.
+
 2017-06-16  H.J. Lu  <hongjiu.lu@intel.com>
 
        * elf/Versions (ld): Remove _dl_out_of_memory.

diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/syscall.S b/sysdeps/unix/sysv/linux/s390/s390-32/syscall.S
index 8506db1..0fa08cd 100644 (file)
--- a/sysdeps/unix/sysv/linux/s390/s390-32/syscall.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/syscall.S
@@ -49,19 +49,13 @@ ENTRY (syscall)
        l      %r6,192(%r15)       /* fifth parameter  */
        l      %r7,196(%r15)       /* sixth parameter  */
 
-       basr   %r8,0
-0:     cl     %r1,4f-0b(%r8)      /* svc number < 256? */
-       jl     2f
-1:     svc    0
-       j      3f
-2:     ex     %r1,1b-0b(%r8)      /* lsb of R1 is subsituted as SVC number */
-3:     l      %r15,0(%r15)        /* load back chain */
+       svc    0
+       l      %r15,0(%r15)        /* load back chain.  */
        cfi_adjust_cfa_offset (-96)
-       lm     %r6,15,24(%r15)     /* load registers */
+       lm     %r6,%r15,24(%r15)   /* load registers.  */
 
        lhi    %r0,-4095
        clr    %r2,%r0             /* check R2 for error */
        jnl    SYSCALL_ERROR_LABEL
        br     %r14                /* return to caller */
-4:     .long  256
 PSEUDO_END (syscall)

diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/syscall.S b/sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
index 24c47cb..61e2485 100644 (file)
--- a/sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
@@ -49,20 +49,14 @@ ENTRY (syscall)
        lg     %r6,320(%r15)       /* Fifth parameter.  */
        lg     %r7,328(%r15)       /* Sixth parameter.  */
 
-       basr   %r8,0
-0:     clg    %r1,4f-0b(%r8)      /* svc number < 256? */
-       jl     2f
-1:     svc    0
-       j      3f
-2:     ex     %r1,1b-0b(%r8)      /* lsb of R1 is subsituted as SVC number */
-3:     lg     %r15,0(%r15)        /* load back chain */
+       svc    0
+       lg     %r15,0(%r15)        /* Load back chain.  */
        cfi_adjust_cfa_offset (-160)
-       lmg     %r6,15,48(%r15)    /* Load registers.  */
+       lmg    %r6,%r15,48(%r15)   /* Load registers.  */
 
        lghi   %r0,-4095
        clgr   %r2,%r0             /* Check R2 for error.  */
        jgnl   SYSCALL_ERROR_LABEL
        br     %r14                /* Return to caller.  */
-4:     .quad  256
 PSEUDO_END (syscall)