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Add a new constructor for empty XArrays, VG_(newSizedXA). This is

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identical to VG_(newXA) but allows passing in a size hint.  In the
case where the likely final size of the XArray is known at creation
time, this allows avoiding the repeated (implicit) resizing and
copying of the array as elements are added, which can save a vast
amount of dynamic memory allocation turnover.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@11568
This commit is contained in:
Julian Seward 2011-02-23 13:22:24 +00:00
parent 0e228dac5d
commit 0c2371837b
2 changed files with 32 additions and 2 deletions
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23
coregrind/m_xarray.c
View File

@ -44,6 +44,7 @@ struct _XArray {
Int (*cmpFn) ( void*, void* ); /* cmp fn (may be NULL) */
Word elemSzB; /* element size in bytes */
void* arr; /* pointer to elements */
Word initsizeE; /* HINT only: initial size, 0 if no hint */
Word usedsizeE; /* # used elements in arr */
Word totsizeE; /* max size of arr, in elements */
Bool sorted; /* is it sorted? */
@ -72,6 +73,7 @@ XArray* VG_(newXA) ( void*(*alloc_fn)(HChar*,SizeT),
xa->free = free_fn;
xa->cmpFn = NULL;
xa->elemSzB = elemSzB;
xa->initsizeE = 0;
xa->usedsizeE = 0;
xa->totsizeE = 0;
xa->sorted = False;
@ -79,6 +81,19 @@ XArray* VG_(newXA) ( void*(*alloc_fn)(HChar*,SizeT),
return xa;
}
XArray* VG_(newSizedXA) ( void*(*alloc_fn)(HChar*,SizeT),
HChar* cc,
void(*free_fn)(void*),
Word elemSzB,
Word nInitialElems )
{
XArray* xa;
tl_assert(nInitialElems >= 0);
xa = VG_(newXA)( alloc_fn, cc, free_fn, elemSzB );
xa->initsizeE = nInitialElems;
return xa;
}
XArray* VG_(cloneXA)( HChar* cc, XArray* xao )
{
struct _XArray* xa = (struct _XArray*)xao;
@ -145,7 +160,7 @@ inline void* VG_(indexXA) ( XArray* xao, Word n )
static inline void ensureSpaceXA ( struct _XArray* xa )
{
if (xa->usedsizeE == xa->totsizeE) {
if (UNLIKELY(xa->usedsizeE == xa->totsizeE)) {
void* tmp;
Word newsz;
if (xa->totsizeE == 0)
@ -158,7 +173,11 @@ static inline void ensureSpaceXA ( struct _XArray* xa )
Hence increase the initial array size for tiny elements in
an attempt to avoid reallocations of size 2, 4, 8 if the
array does start to fill up. */
if (xa->elemSzB == 1) newsz = 8;
/* Also, if there's a hinted initial size, use that instead of
the logic in the preceding comment. */
tl_assert(xa->initsizeE >= 0);
if (xa->initsizeE > 0) newsz = xa->initsizeE;
else if (xa->elemSzB == 1) newsz = 8;
else if (xa->elemSzB == 2) newsz = 4;
else newsz = 2;
} else {

11
include/pub_tool_xarray.h
View File

@ -54,6 +54,17 @@ extern XArray* VG_(newXA) ( void*(*alloc_fn)(HChar*,SizeT),
void(*free_fn)(void*),
Word elemSzB );
/* Same as VG_(newXA), except allows specification of an initial
number of elements for the array, so as to avoid a potentially
large wasted cost of repeatedly resizing the array when the caller
knows something about what the expected final size is going to
be. */
extern XArray* VG_(newSizedXA) ( void*(*alloc_fn)(HChar*,SizeT),
HChar* cc,
void(*free_fn)(void*),
Word elemSzB,
Word nInitialElems );
/* Free all memory associated with an XArray. */
extern void VG_(deleteXA) ( XArray* );