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VM: Keep jump table address in a register.

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* libguile/vm-engine.c (VM_NAME)[HAVE_LABELS_AS_VALUES]: Rename
  `jump_table' to `jump_table_pointer'.  Add `jump_table' as a local
  variable, initialize it.

* libguile/vm-engine.h (JT_REG): New macro.
This commit is contained in:
Ludovic Courtès 2011-07-04 23:56:16 +02:00
parent c467c36374
commit 37a5970c19
2 changed files with 21 additions and 5 deletions
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18
libguile/vm-engine.c
View file

@ -61,23 +61,31 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
SCM finish_args; /* used both for returns: both in error
and normal situations */
#ifdef HAVE_LABELS_AS_VALUES
static void **jump_table = NULL;
static const void **jump_table_pointer = NULL;
#endif
#ifdef HAVE_LABELS_AS_VALUES
if (SCM_UNLIKELY (!jump_table))
register const void **jump_table JT_REG;
if (SCM_UNLIKELY (!jump_table_pointer))
{
int i;
jump_table = malloc (SCM_VM_NUM_INSTRUCTIONS * sizeof(void*));
jump_table_pointer = malloc (SCM_VM_NUM_INSTRUCTIONS * sizeof (void*));
for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
jump_table[i] = &&vm_error_bad_instruction;
jump_table_pointer[i] = &&vm_error_bad_instruction;
#define VM_INSTRUCTION_TO_LABEL 1
#define jump_table jump_table_pointer
#include <libguile/vm-expand.h>
#include <libguile/vm-i-system.i>
#include <libguile/vm-i-scheme.i>
#include <libguile/vm-i-loader.i>
#undef jump_table
#undef VM_INSTRUCTION_TO_LABEL
}
/* Attempt to keep JUMP_TABLE_POINTER in a register. This saves one
load instruction at each instruction dispatch. */
jump_table = jump_table_pointer;
#endif
/* Initialization */

8
libguile/vm-engine.h
View file

@ -57,6 +57,11 @@
/* too few registers! because of register allocation errors with various gcs,
just punt on explicit assignments on i386, hoping that the "register"
declaration will be sufficient. */
#elif defined __x86_64__
/* GCC 4.6 chooses %rbp for IP_REG and %rbx for SP_REG, which works
well. Tell it to keep the jump table in a r12, which is
callee-saved. */
#define JT_REG asm ("r12")
#endif
#if defined(PPC) || defined(_POWER) || defined(_IBMR2)
#define IP_REG asm("26")
@ -89,6 +94,9 @@
#ifndef FP_REG
#define FP_REG
#endif
#ifndef JT_REG
#define JT_REG
#endif
/*