> it's not idiomatic for the language What do you mean? Serious question, not sarcasm.
Certainly it is architecture dependent, but then, any time you cast a pointer to a long you are in architecture land. > I wonder how much it's used by assembler programmers? I personally do not, because we have made a decision to stick to ZS-3 (z9) for our assembler code. (The C code goes out the door ARCH(9) but it is trivial to recompile for any ARCH level.) The z9 is supported by V2R1 which itself is still on support. We will probably upgrade everything one of these days but (1) there is little incentive to change working non-critical-performance-path assembler and (2) we do very little new assembler. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of David Crayford Sent: Friday, July 20, 2018 1:50 AM To: [email protected] Subject: Re: S0C6 in CSRC4RG1 I don't like using negative numbers in C code because it's not idiomatic for the language and I'm pedantic :) The C compiler uses a XILF instruction to implement to compliment operator and does the AND with a NRK instruction. The distinct operand facility is interesting. It's for register constraint relief. I wonder how much it's used by assembler programmers? aligned_malloc 000006 | DS 0D 000006 | STM r6,r10,1928(r4) 000006 | LAY r4,-128(,r4) End of Prolog 000011 | L r6,=A(malloc)(,r5,12) 000010 | ALHSIK r10,r2,H'-1' 000010 | ALHSIK r0,r2,H'3' 000007 | * { 000008 | * void * ptr = NULL; 000008 | LA r8,0 000011 | L r5,=A(malloc)(,r5,8) 000009 | * // allocate storage area with space for an extra pointer and alignment 000010 | * size += sizeof(void *) + (align - 1); 000010 | ALRK r9,r1,r0 000011 | * void * mem = malloc(size); 000011 | LR r1,r9 000011 | BASR r7,r6 000011 | NOP 6 000012 | * if (mem) { 000012 | CIJE r3,H'0',@2L2 000013 | * // point to the start of the aligned storage to return 000014 | * ptr = (void **)((uintptr_t)(mem + size) & ~(align - 1)); 000014 | LA r0,#AddressShadow(r9,r3,0) 000014 | XILF r10,F'-1' 000014 | NRK r8,r0,r10 000015 | * // store the address of the allocated memory prior to the aligned storage 000016 | * ((void **) ptr)[-1] = mem; 000016 | STY r3,(*)void*(,r8,-4) 000016 | @2L2 DS 0H 000017 | * } 000018 | * return ptr; 000018 | LR r3,r8 000019 | * } 000019 | @2L3 DS 0H Start of Epilog 000019 | LM r7,r10,2060(r4) 000019 | LA r4,128(,r4) 000019 | B 4(,r7) Start of Epilog 000017 | LM r7,r9,2060(r4) 000017 | LA r4,128(,r4) 000017 | B 4(,r7) On 19/07/2018 10:43 PM, Steve Smith wrote: > Thank-you Mr. Relson! > > Oddly enough, in rerunning my test, it seems that it fails considerably > less than half the time. That is, it usually aligns on a 16-byte > boundary. This test version is configured to allocate the cpool anchor and > extent, plus four 160-byte buffers. This is to stress-test buffer > exhaustion logic. The production version uses 4091* buffers, making the > total space just under 640KB (which as we all know, should be enough for > anybody). That has never failed to align correctly. > > * The idea is to *avoid* buffer exhaustion, and presently, this seems to be > enough. > > Re specification of rounding mask: I do think -16, -8, etc. are an elegant > way to specify these, particularly as they correlate to 16-byte, 8-byte, > etc. boundaries. I sure wish they were usable with NILL and NILF. > > Well, I decided to check before complaining... and (surprise!): > > 0000028C 0000 0000 00000000 481 NILL > R15,-4 > ** ASMA031E Invalid immediate or mask > field > 00000290 C0FB FFFF FFF0 00000000 482 NILF > R15,-16 > 483 > * > > Sigh. > > sas > > > On Thu, Jul 19, 2018 at 8:01 AM, Peter Relson <[email protected]> wrote: > >>> Problems: >>> 1. Undocumented requirement to quad-word align CPOOL anchor and/or >> extent >>> in 64-bit mode (and actually undocumented alignment requirements for >> all). >>> 2. Unable to guarantee quad-word alignment with malloc. >> I will get the first taken care of. The anchor does not need to be >> quad-word aligned. >> >> For the second, as has been pointed out in C syntax but I think not in >> words, you would do what everyone used to do prior to STARTBDY keyword of >> GETMAIN / STORAGE OBTAIN -- round the start address up to the necessary >> boundary, having gotten an additional 8 if you need the length to be some >> specific value (or 15 if you do are not guaranteed that the area will at >> least be on a doubleword boundary). >> >> The rounding is typically "Add 15, AND with -16". >> >> Peter Relson >> z/OS Core Technology Design > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
