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Changes suggested by Ingo: style fix, and a system_time optimization.

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This commit is contained in:
Alex Smith
2012-07-09 09:03:11 +01:00
parent 93cba1da96
commit bc3093488f
2 changed files with 11 additions and 6 deletions
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src/system/boot/platform/bios_ia32/mmu.cpp
+1 -1
View File
@@ -522,7 +522,7 @@ mmu_get_virtual_mapping(addr_t virtualAddress, addr_t *_physicalAddress)
if ((tableEntry & (1 << 0)) == 0) if ((tableEntry & (1 << 0)) == 0)
return false; return false;
*_physicalAddress = tableEntry & 0xFFFFF000; *_physicalAddress = tableEntry & 0xfffff000;
return true; return true;
} }
src/system/libroot/os/arch/x86_64/system_time_asm.S
+10 -5
View File
@@ -28,7 +28,10 @@ FUNCTION_END(__x86_setup_system_time)
/* int64 system_time(); */ /* int64 system_time(); */
FUNCTION(system_time): FUNCTION(system_time):
// (rdtsc * cv_factor) >> 32.
movq cv_factor, %rcx movq cv_factor, %rcx
shl $32, %rcx
// Load 64-bit TSC into %eax (low), %edx (high). // Load 64-bit TSC into %eax (low), %edx (high).
rdtsc rdtsc
@@ -40,17 +43,19 @@ FUNCTION(system_time):
// Multiply by conversion factor, result in %rax (low), %rdx (high). // Multiply by conversion factor, result in %rax (low), %rdx (high).
mulq %rcx mulq %rcx
// Shift the result right by 32 bits. // Conversion factor preshifted by 32, whole result in high.
shr $32, %rax movq %rdx, %rax
shl $32, %rdx
orq %rdx, %rax
ret ret
FUNCTION_END(system_time) FUNCTION_END(system_time)
/* int64 system_time_nsecs(); */ /* int64 system_time_nsecs(); */
FUNCTION(system_time_nsecs): FUNCTION(system_time_nsecs):
// Same algorithm as system_time(), just with a different factor. // Same algorithm as system_time(), but with a different factor.
// (rdtsc * cv_factor_nsecs) >> 32.
// Cannot pre-shift the factor here, otherwise we may lose the upper
// 32 bits.
movq cv_factor_nsecs, %rcx movq cv_factor_nsecs, %rcx
// Load 64-bit TSC into %eax (low), %edx (high). // Load 64-bit TSC into %eax (low), %edx (high).