| Message ID | DB6PR0801MB2053457858AEF015746EC80B835E0@DB6PR0801MB2053.eurprd08.prod.outlook.com |
|---|---|
| State | New |
| Headers | show |
| Series | [AArch64] Define MALLOC_ABI_ALIGNMENT | expand |
On Tue, Oct 31, 2017 at 05:07:54PM +0000, Wilco Dijkstra wrote: > The AArch64 backend currently doesn't set MALLOC_ABI_ALIGNMENT, so > add this to enable alignment optimizations on malloc pointers. > > OK for commit? As far as I understand it, because we have 128-bit types, a malloc of anything greater than 16 bytes would require 16-byte alignment. So, assuming this macro isn't required to desribe possibly unaligned smaller allocations (for example 1 byte allocations), this is OK. Reviewed-By: James Greenhalgh <james.greenhalgh@arm.com> Thanks, James > > 2017-10-31 Wilco Dijkstra <wdijkstr@arm.com> > > * config/aarch64/aarch64.h (MALLOC_ABI_ALIGNMENT): New define. > -- > diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h > index 8e7093f0476fa7fed3ba6d6cb008743106d1ff58..159dde7c7134d4d0e5378951d1d8a1d6dab48ba2 100644 > --- a/gcc/config/aarch64/aarch64.h > +++ b/gcc/config/aarch64/aarch64.h > @@ -111,6 +111,9 @@ > > #define STRUCTURE_SIZE_BOUNDARY 8 > > +/* Heap alignment. */ > +#define MALLOC_ABI_ALIGNMENT BIGGEST_ALIGNMENT > + > /* Defined by the ABI */ > #define WCHAR_TYPE "unsigned int" > #define WCHAR_TYPE_SIZE 32
On 01/11/17 17:40, James Greenhalgh wrote: > On Tue, Oct 31, 2017 at 05:07:54PM +0000, Wilco Dijkstra wrote: >> The AArch64 backend currently doesn't set MALLOC_ABI_ALIGNMENT, so >> add this to enable alignment optimizations on malloc pointers. >> >> OK for commit? > > As far as I understand it, because we have 128-bit types, a malloc of > anything greater than 16 bytes would require 16-byte alignment. So, assuming > this macro isn't required to desribe possibly unaligned smaller allocations > (for example 1 byte allocations), this is OK. > > Reviewed-By: James Greenhalgh <james.greenhalgh@arm.com> > > Thanks, > James > >> >> 2017-10-31 Wilco Dijkstra <wdijkstr@arm.com> >> >> * config/aarch64/aarch64.h (MALLOC_ABI_ALIGNMENT): New define. >> -- >> diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h >> index 8e7093f0476fa7fed3ba6d6cb008743106d1ff58..159dde7c7134d4d0e5378951d1d8a1d6dab48ba2 100644 >> --- a/gcc/config/aarch64/aarch64.h >> +++ b/gcc/config/aarch64/aarch64.h >> @@ -111,6 +111,9 @@ >> >> #define STRUCTURE_SIZE_BOUNDARY 8 >> >> +/* Heap alignment. */ >> +#define MALLOC_ABI_ALIGNMENT BIGGEST_ALIGNMENT >> + >> /* Defined by the ABI */ >> #define WCHAR_TYPE "unsigned int" >> #define WCHAR_TYPE_SIZE 32 I wonder if it would be safer to define this explicitly as the current value of BIGGEST_ALIGNMENT; then if we ever have to change the latter we won't get silent breakage. R.
Richard Earnshaw wrote: > On 01/11/17 17:40, James Greenhalgh wrote: >> As far as I understand it, because we have 128-bit types, a malloc of >> anything greater than 16 bytes would require 16-byte alignment. So, assuming >> this macro isn't required to desribe possibly unaligned smaller allocations >> (for example 1 byte allocations), this is OK. I'm sure one can create structures with 16-byte alignment that are smaller than 16 bytes. For example union of say a char and __int128 empty_array[0] should do it. >> +#define MALLOC_ABI_ALIGNMENTÂ BIGGEST_ALIGNMENT > I wonder if it would be safer to define this explicitly as the current > value of BIGGEST_ALIGNMENT; then if we ever have to change the latter we > won't get silent breakage. I'll do that for the commit. I used BIGGEST_ALIGNMENT since that is what the Arm port does... Wilco
diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h index 8e7093f0476fa7fed3ba6d6cb008743106d1ff58..159dde7c7134d4d0e5378951d1d8a1d6dab48ba2 100644 --- a/gcc/config/aarch64/aarch64.h +++ b/gcc/config/aarch64/aarch64.h @@ -111,6 +111,9 @@ #define STRUCTURE_SIZE_BOUNDARY 8 +/* Heap alignment. */ +#define MALLOC_ABI_ALIGNMENT BIGGEST_ALIGNMENT + /* Defined by the ABI */ #define WCHAR_TYPE "unsigned int" #define WCHAR_TYPE_SIZE 32