RFR(S): 8085932: Fixing bugs in detecting memory alignments in SuperWord (original) (raw)

Vladimir Kozlov vladimir.kozlov at oracle.com
Fri Jun 19 00:51:33 UTC 2015

Jan,

Here is why next code return false:

if (_scale != 0) { return false; // already found a scale

if (_invar != NULL) return false; // already have an invariant

SWPointer() method tries to set _scale, _offset, _invar values. But, for example, simple array access address uses 2 AddP nodes and each of them has offsets but different offsets. Usually one have invariant offset and another - scaled index:

AddP (base, base, iv*scale + offset) AddP (base, addp, invar)

SWPointer() iterates over all AddP:

for (int i = 0; i < 3; i++) { if (!scaled_iv_plus_offset(adr->in(AddPNode::Offset))) { assert(!valid(), "too complex"); return; } adr = adr->in(AddPNode::Address); if (base == adr || !adr->is_AddP()) { break; // stop looking at addp's } }

And this code assumes only one of AddP can set those fields (_scale, _offset, _invar). If second AddP tries to set a field which is set by previous AddP it is considered complex address expression, for example:

AddP (base, base, iv*scale + offset_con + invar1) AddP (base, addp, invar2)

and such cases are skipped.

Please, show your case for which you want to return 'true'.

Thanks, Vladimir

On 6/18/15 5:10 PM, Vladimir Kozlov wrote:

Thank you, Jan

Fixes looks good but it would be nice if you replaced some tracing code with functions calls. In some place the execution code is hard to read because of big tracing code. For example, in SuperWord::memoryalignment() and in SWPointer methods. The one way to do that is to declare trace methods with empty body in product build, for example for SWPointer::scaledivplusoffset() you may have new method declaration (not under #ifdef) in superword.hpp: class SWPointer VALUEOBJCLASSSPEC { void trace1scaledivplusoffset(...) PRODUCTRETURN; and in superword.cpp you will put the method under ifdef: #ifndef PRODUCT void trace1scaledivplusoffset(...) { .... } #endif Then you can simply use it without ifdefs in code: bool SWPointer::scaledivplusoffset(Node* n) { + trace1scaledivplusoffset(...); + if (scalediv(n)) { Note, macro PRODUCTRETURN is defined as: #ifdef PRODUCT #define PRODUCTRETURN {} #else #define PRODUCTRETURN /next token must be ;/ #endif Thanks, Vladimir On 6/8/15 9:15 AM, Civlin, Jan wrote: Hi All,

We would like to contribute to Fixing bugs in detecting memory alignments in SuperWord. The contribution Bug ID: 8085932. Please review this patch: Bug-id: https://bugs.openjdk.java.net/browse/JDK-8085932 webrev: http://cr.openjdk.java.net/~kvn/8085932/webrev.00/ Description*: *Fixing bugs in detecting memory alignments in SuperWord Fixing bugs in detecting memory alignments in SuperWord: SWPointer::scaledivplusoffset (fixing here a bug in detection of "scale"), SWPointer::offsetplusk (fixing here a bug in detection of "invariant"), Add tracing output to the code that deal with memory alignment. The following routines are traceable: SWPointer::scaledivplusoffset SWPointer::offsetplusk SWPointer::scalediv, WPointer::SWPointer, SuperWord::memoryalignment Tracing is done only for NOTPRODUCT. Currently tracing is controlled by VectorizeDebug: #ifndef PRODUCT if (phase->C->method() != NULL) { phase->C->method()->hasoptionvalue("VectorizeDebug", vectorloopdebug); } #endif And VectorizeDebug may take any combination (bitwise OR) of the following values: bool istracealignment() { return (vectorloopdebug & 2) > 0; } bool istracememslice() { return (vectorloopdebug & 4) > 0; } bool istraceloop() { return (vectorloopdebug & 8) > 0; } bool istraceadjacent() { return (vectorloopdebug & 16) > 0; }

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