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| author | Keir Fraser <keir@xen.org> | 2010-12-16 18:37:20 +0000 |
|---|---|---|
| committer | Keir Fraser <keir@xen.org> | 2010-12-16 18:37:20 +0000 |
| commit | c69d84d0a9937aac19dfe10afe64df3bc2c74aed (patch) | |
| tree | ce24dd8fb28a36acf014997ce2291818a4fb1389 /xen/arch/x86/x86_64/entry.S | |
| parent | d4700445c1b02a9d9e2ad8806445c5dffb4e2c53 (diff) | |
| download | xen-c69d84d0a9937aac19dfe10afe64df3bc2c74aed.tar.gz xen-c69d84d0a9937aac19dfe10afe64df3bc2c74aed.tar.bz2 xen-c69d84d0a9937aac19dfe10afe64df3bc2c74aed.zip | |
x86/asm: allow some unlikely taken branches to be statically predicted this way
... by moving the respective code out of line (into sub-section 1 of
the particular section). A few other branches could be eliminated
altogether.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Diffstat (limited to 'xen/arch/x86/x86_64/entry.S')
| -rw-r--r-- | xen/arch/x86/x86_64/entry.S | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index 70471ecfc6..27effbdae7 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -152,7 +152,7 @@ ENTRY(syscall_enter) #define SHADOW_BYTES 0 /* No on-stack shadow state */ #endif cmpb $0,tb_init_done(%rip) - je 1f +UNLIKELY_START(ne, trace) call trace_hypercall /* Now restore all the registers that trace_hypercall clobbered */ movq UREGS_rax+SHADOW_BYTES(%rsp),%rax /* Hypercall # */ @@ -163,7 +163,8 @@ ENTRY(syscall_enter) movq UREGS_r8 +SHADOW_BYTES(%rsp),%r8 /* Arg 5 */ movq UREGS_r9 +SHADOW_BYTES(%rsp),%r9 /* Arg 6 */ #undef SHADOW_BYTES -1: leaq hypercall_table(%rip),%r10 +UNLIKELY_END(trace) + leaq hypercall_table(%rip),%r10 PERFC_INCR(PERFC_hypercalls, %rax, %rbx) callq *(%r10,%rax,8) #ifndef NDEBUG @@ -345,11 +346,12 @@ create_bounce_frame: 2: andq $~0xf,%rsi # Stack frames are 16-byte aligned. movq $HYPERVISOR_VIRT_START,%rax cmpq %rax,%rsi - jb 1f # In +ve address space? Then okay. movq $HYPERVISOR_VIRT_END+60,%rax + sbb %ecx,%ecx # In +ve address space? Then okay. cmpq %rax,%rsi - jb domain_crash_synchronous # Above Xen private area? Then okay. -1: movb TRAPBOUNCE_flags(%rdx),%cl + adc %ecx,%ecx # Above Xen private area? Then okay. + jg domain_crash_synchronous + movb TRAPBOUNCE_flags(%rdx),%cl subq $40,%rsi movq UREGS_ss+8(%rsp),%rax .Lft2: movq %rax,32(%rsi) # SS @@ -380,7 +382,7 @@ create_bounce_frame: movl TRAPBOUNCE_error_code(%rdx),%eax .Lft7: movq %rax,(%rsi) # ERROR CODE 1: testb $TBF_FAILSAFE,%cl - jz 2f +UNLIKELY_START(nz, bounce_failsafe) subq $32,%rsi movl %gs,%eax .Lft8: movq %rax,24(%rsi) # GS @@ -390,7 +392,8 @@ create_bounce_frame: .Lft10: movq %rax,8(%rsi) # ES movl %ds,%eax .Lft11: movq %rax,(%rsi) # DS -2: subq $16,%rsi +UNLIKELY_END(bounce_failsafe) + subq $16,%rsi movq UREGS_r11+8(%rsp),%rax .Lft12: movq %rax,8(%rsi) # R11 movq UREGS_rcx+8(%rsp),%rax |