| Message ID | 20110622193657.GA8942@intel.com |
|---|---|
| State | New |
| Headers | show |
> I just don't see how nonzero_bits1 can assume if pointers extend unsigned > and this is an addition or subtraction to a pointer in Pmode, all the bits > bove ptr_mode are known to be zero. We never run into it before x32 > since x32 is the first such target. I agree that this is overly optimistical, but this was done on purpose: http://gcc.gnu.org/ml/gcc-patches/2001-02/msg00316.html Could you evaluate the pessimization that the patch introduces (if any) for the generated code on x32? If there is none or it is negligible, the patch is OK if completed by the removal of the equivalent code in num_sign_bit_copies1. If it isn't negligible, we may need to be clever and devise something else.
On Fri, Jun 24, 2011 at 1:58 AM, Eric Botcazou <ebotcazou@adacore.com> wrote: >> I just don't see how nonzero_bits1 can assume if pointers extend unsigned >> and this is an addition or subtraction to a pointer in Pmode, all the bits >> bove ptr_mode are known to be zero. We never run into it before x32 >> since x32 is the first such target. > > I agree that this is overly optimistical, but this was done on purpose: > http://gcc.gnu.org/ml/gcc-patches/2001-02/msg00316.html > > Could you evaluate the pessimization that the patch introduces (if any) for the > generated code on x32? If there is none or it is negligible, the patch is OK > if completed by the removal of the equivalent code in num_sign_bit_copies1. > If it isn't negligible, we may need to be clever and devise something else. > I compared x32 glibc built with the old x32 gcc against x32 glibc built with this patch and http://gcc.gnu.org/ml/gcc-patches/2011-06/msg00913.html reverted, the new glibc is little smaller: New: [hjl@gnu-33 build-x86_64-linux]$ size libc.so text data bss dec hex filename 1537648 10076 12944 1560668 17d05c libc.so [hjl@gnu-33 build-x86_64-linux]$ Old: [hjl@gnu-33 build-x86_64-linux.old]$ size libc.so text data bss dec hex filename 1538968 10076 12944 1561988 17d584 libc.so [hjl@gnu-33 build-x86_64-linux.old]$ I looked at assembly codes. The new one is better. I will check it in. Thanks.
> I compared x32 glibc built with the old x32 gcc against x32 glibc built > with this patch and > > http://gcc.gnu.org/ml/gcc-patches/2011-06/msg00913.html > > reverted, the new glibc is little smaller: > > New: > > [hjl@gnu-33 build-x86_64-linux]$ size libc.so > text data bss dec hex filename > 1537648 10076 12944 1560668 17d05c libc.so > [hjl@gnu-33 build-x86_64-linux]$ > > Old: > > [hjl@gnu-33 build-x86_64-linux.old]$ size libc.so > text data bss dec hex filename > 1538968 10076 12944 1561988 17d584 libc.so > [hjl@gnu-33 build-x86_64-linux.old]$ > > I looked at assembly codes. The new one is better. > I will check it in. OK, but remove the equivalent code in num_sign_bit_copies1 then, otherwise someone in a couple of years from now will adapt it to nonzero_bits1 and we will be back to square one.
diff --git a/gcc/ChangeLog.x32 b/gcc/ChangeLog.x32 index 564e123..9bbb05b 100644 --- a/gcc/ChangeLog.x32 +++ b/gcc/ChangeLog.x32 @@ -1,3 +1,9 @@ +2011-06-22 H.J. Lu <hongjiu.lu@intel.com> + + PR rtl-optimization/49504 + * rtlanal.c (nonzero_bits1): Properly handle addition or + subtraction a pointer in Pmode if pointers extend unsigned. + 2011-06-15 H.J. Lu <hongjiu.lu@intel.com> PR middle-end/48016 diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c index b52957d..e5c045d 100644 --- a/gcc/rtlanal.c +++ b/gcc/rtlanal.c @@ -4134,20 +4134,6 @@ nonzero_bits1 (const_rtx x, enum machine_mode mode, const_rtx known_x, if (result_low > 0) nonzero &= ~(((unsigned HOST_WIDE_INT) 1 << result_low) - 1); - -#ifdef POINTERS_EXTEND_UNSIGNED - /* If pointers extend unsigned and this is an addition or subtraction - to a pointer in Pmode, all the bits above ptr_mode are known to be - zero. */ - /* As we do not know which address space the pointer is refering to, - we can do this only if the target does not support different pointer - or address modes depending on the address space. */ - if (target_default_pointer_address_modes_p () - && POINTERS_EXTEND_UNSIGNED > 0 && GET_MODE (x) == Pmode - && (code == PLUS || code == MINUS) - && REG_P (XEXP (x, 0)) && REG_POINTER (XEXP (x, 0))) - nonzero &= GET_MODE_MASK (ptr_mode); -#endif } break; diff --git a/gcc/testsuite/ChangeLog.x32 b/gcc/testsuite/ChangeLog.x32 index ab8dd76..6581a45 100644 --- a/gcc/testsuite/ChangeLog.x32 +++ b/gcc/testsuite/ChangeLog.x32 @@ -1,3 +1,8 @@ +2011-06-22 H.J. Lu <hongjiu.lu@intel.com> + + PR rtl-optimization/49504 + * gcc.target/i386/pr49504.c: New. + 2011-06-15 H.J. Lu <hongjiu.lu@intel.com> * gcc.dg/pr44194-1.c: Also allow x32. diff --git a/gcc/testsuite/gcc.target/i386/pr49504.c b/gcc/testsuite/gcc.target/i386/pr49504.c new file mode 100644 index 0000000..9128196 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr49504.c @@ -0,0 +1,18 @@ +/* PR target/49504 */ +/* { dg-do run { target { x32 } } } */ +/* { dg-options "-O" } */ + +unsigned long long +foo (const void* p, unsigned long long q) +{ + unsigned long long a = (((unsigned long long) ((unsigned long) p)) + q) >> 32; + return a; +} + +int +main () +{ + if (foo ((const void*) 0x100, 0x100000000ULL) == 0) + __builtin_abort (); + return 0; +}