#include "llvm/Support/MathExtras.h"
#include "llvm/ADT/Statistic.h"
#include <set>
+#include <map>
#include <algorithm>
using namespace llvm;
/// IA64Lowering - This object fully describes how to lower LLVM code to an
/// IA64-specific SelectionDAG.
IA64TargetLowering IA64Lowering;
+ SelectionDAG *ISelDAG; // Hack to support us having a dag->dag transform
+ // for sdiv and udiv until it is put into the future
+ // dag combiner
/// ExprMap - As shared expressions are codegen'd, we keep track of which
/// vreg the value is produced in, so we only emit one copy of each compiled
std::set<SDOperand> LoweredTokens;
public:
- ISel(TargetMachine &TM) : SelectionDAGISel(IA64Lowering), IA64Lowering(TM) {
- }
+ ISel(TargetMachine &TM) : SelectionDAGISel(IA64Lowering), IA64Lowering(TM),
+ ISelDAG(0) { }
/// InstructionSelectBasicBlock - This callback is invoked by
/// SelectionDAGISel when it has created a SelectionDAG for us to codegen.
unsigned SelectExpr(SDOperand N);
void Select(SDOperand N);
+ // a dag->dag to transform mul-by-constant-int to shifts+adds/subs
+ SDOperand BuildConstmulSequence(SDOperand N);
+
};
}
void ISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
// Codegen the basic block.
+ ISelDAG = &DAG;
Select(DAG.getRoot());
// Clear state used for selection.
ExprMap.clear();
LoweredTokens.clear();
+ ISelDAG = 0;
+}
+
+const char sign[2]={'+','-'};
+
+
+// strip leading '0' characters from a string
+void munchLeadingZeros(std::string& inString) {
+ while(inString.c_str()[0]=='0') {
+ inString.erase(0, 1);
+ }
+}
+
+// strip trailing '0' characters from a string
+void munchTrailingZeros(std::string& inString) {
+ int curPos=inString.length()-1;
+
+ while(inString.c_str()[curPos]=='0') {
+ inString.erase(curPos, 1);
+ curPos--;
+ }
+}
+
+// return how many consecutive '0' characters are at the end of a string
+unsigned int countTrailingZeros(std::string& inString) {
+ int curPos=inString.length()-1;
+ unsigned int zeroCount=0;
+ // assert goes here
+ while(inString.c_str()[curPos--]=='0') {
+ zeroCount++;
+ }
+ return zeroCount;
+}
+
+// booth encode a string of '1' and '0' characters (returns string of 'P' (+1)
+// '0' and 'N' (-1) characters)
+void boothEncode(std::string inString, std::string& boothEncodedString) {
+
+ int curpos=0;
+ int replacements=0;
+ int lim=inString.size();
+
+ while(curpos<lim) {
+ if(inString[curpos]=='1') { // if we see a '1', look for a run of them
+ int runlength=0;
+ std::string replaceString="N";
+
+ // find the run length
+ for(;inString[curpos+runlength]=='1';runlength++) ;
+
+ for(int i=0; i<runlength-1; i++)
+ replaceString+="0";
+ replaceString+="1";
+
+ if(runlength>1) {
+ inString.replace(curpos, runlength+1, replaceString);
+ curpos+=runlength-1;
+ } else
+ curpos++;
+ } else { // a zero, we just keep chugging along
+ curpos++;
+ }
+ }
+
+ // clean up (trim the string, reverse it and turn '1's into 'P's)
+ munchTrailingZeros(inString);
+ boothEncodedString="";
+
+ for(int i=inString.size()-1;i>=0;i--)
+ if(inString[i]=='1')
+ boothEncodedString+="P";
+ else
+ boothEncodedString+=inString[i];
+
+}
+
+struct shiftaddblob { // this encodes stuff like (x=) "A << B [+-] C << D"
+ unsigned firstVal; // A
+ unsigned firstShift; // B
+ unsigned secondVal; // C
+ unsigned secondShift; // D
+ bool isSub;
+};
+
+/* this implements Lefevre's "pattern-based" constant multiplication,
+ * see "Multiplication by an Integer Constant", INRIA report 1999-06
+ *
+ * TODO: implement a method to try rewriting P0N<->0PP / N0P<->0NN
+ * to get better booth encodings - this does help in practice
+ * TODO: weight shifts appropriately (most architectures can't
+ * fuse a shift and an add for arbitrary shift amounts) */
+unsigned lefevre(const std::string inString,
+ std::vector<struct shiftaddblob> &ops) {
+ std::string retstring;
+ std::string s = inString;
+ munchTrailingZeros(s);
+
+ int length=s.length()-1;
+
+ if(length==0) {
+ return(0);
+ }
+
+ std::vector<int> p,n;
+
+ for(int i=0; i<=length; i++) {
+ if (s.c_str()[length-i]=='P') {
+ p.push_back(i);
+ } else if (s.c_str()[length-i]=='N') {
+ n.push_back(i);
+ }
+ }
+
+ std::string t, u;
+ int c,f;
+ std::map<const int, int> w;
+
+ for(int i=0; i<p.size(); i++) {
+ for(int j=0; j<i; j++) {
+ w[p[i]-p[j]]++;
+ }
+ }
+
+ for(int i=1; i<n.size(); i++) {
+ for(int j=0; j<i; j++) {
+ w[n[i]-n[j]]++;
+ }
+ }
+
+ for(int i=0; i<p.size(); i++) {
+ for(int j=0; j<n.size(); j++) {
+ w[-abs(p[i]-n[j])]++;
+ }
+ }
+
+ std::map<const int, int>::const_iterator ii;
+ std::vector<int> d;
+ std::multimap<int, int> sorted_by_value;
+
+ for(ii = w.begin(); ii!=w.end(); ii++)
+ sorted_by_value.insert(std::pair<int, int>((*ii).second,(*ii).first));
+
+ for (std::multimap<int, int>::iterator it = sorted_by_value.begin();
+ it != sorted_by_value.end(); ++it) {
+ d.push_back((*it).second);
+ }
+
+ int int_W=0;
+ int int_d;
+
+ while(d.size()>0 && (w[int_d=d.back()] > int_W)) {
+ d.pop_back();
+ retstring=s; // hmmm
+ int x=0;
+ int z=abs(int_d)-1;
+
+ if(int_d>0) {
+
+ for(int base=0; base<retstring.size(); base++) {
+ if( ((base+z+1) < retstring.size()) &&
+ retstring.c_str()[base]=='P' &&
+ retstring.c_str()[base+z+1]=='P')
+ {
+ // match
+ x++;
+ retstring.replace(base, 1, "0");
+ retstring.replace(base+z+1, 1, "p");
+ }
+ }
+
+ for(int base=0; base<retstring.size(); base++) {
+ if( ((base+z+1) < retstring.size()) &&
+ retstring.c_str()[base]=='N' &&
+ retstring.c_str()[base+z+1]=='N')
+ {
+ // match
+ x++;
+ retstring.replace(base, 1, "0");
+ retstring.replace(base+z+1, 1, "n");
+ }
+ }
+
+ } else {
+ for(int base=0; base<retstring.size(); base++) {
+ if( ((base+z+1) < retstring.size()) &&
+ ((retstring.c_str()[base]=='P' &&
+ retstring.c_str()[base+z+1]=='N') ||
+ (retstring.c_str()[base]=='N' &&
+ retstring.c_str()[base+z+1]=='P')) ) {
+ // match
+ x++;
+
+ if(retstring.c_str()[base]=='P') {
+ retstring.replace(base, 1, "0");
+ retstring.replace(base+z+1, 1, "p");
+ } else { // retstring[base]=='N'
+ retstring.replace(base, 1, "0");
+ retstring.replace(base+z+1, 1, "n");
+ }
+ }
+ }
+ }
+
+ if(x>int_W) {
+ int_W = x;
+ t = retstring;
+ c = int_d; // tofix
+ }
+
+ } d.pop_back(); // hmm
+
+ u = t;
+
+ for(int i=0; i<t.length(); i++) {
+ if(t.c_str()[i]=='p' || t.c_str()[i]=='n')
+ t.replace(i, 1, "0");
+ }
+
+ /* and now for something completely different:
+
+ //\\\\\\ ` \`..(@)
+ : \\\\ (@)(@) / /(@)
+ \ ~L~ )\\\\ \ \ '\(__``',..
+ /\_~ / |||| \ , | ~~~--/
+ ////| |//// // /
+ ||||^ ~~~~~~--------~/ /
+ / ( ( _____---~~~~~\| /
+( )| / / / /
+ \^\ \____/ / \ /
+ \ \/ \ \ /
+ )) ) ' ~
+ | | ` ,
+ |______|
+ | || | ,
+ ( || |
+ \ | | ,
+ \| /
+ /_^||
+ */
+
+ for(int i=0; i<u.length(); i++) {
+ if(u.c_str()[i]=='P' || u.c_str()[i]=='N')
+ u.replace(i, 1, "0");
+ if(u.c_str()[i]=='p')
+ u.replace(i, 1, "P");
+ if(u.c_str()[i]=='n')
+ u.replace(i, 1, "N");
+ }
+
+ if( c<0 ) {
+ f=1;
+ c=-c;
+ } else
+ f=0;
+
+ bool hit=true;
+ for(int i=0; i<u.length()-1; i++) {
+ if(u.c_str()[i]!='0')
+ hit=false;
+ }
+ if(u.c_str()[u.length()-1]!='N')
+ hit=false;
+
+ int g=0;
+ if(hit) {
+ g=1;
+ for(int p=0; p<u.length(); p++) {
+ bool isP=(u.c_str()[p]=='P');
+ bool isN=(u.c_str()[p]=='N');
+
+ if(isP)
+ u.replace(p, 1, "N");
+ if(isN)
+ u.replace(p, 1, "P");
+ }
+ }
+
+ munchLeadingZeros(u);
+
+ int i = lefevre(u, ops);
+
+ shiftaddblob blob;
+
+ blob.firstVal=i; blob.firstShift=c;
+ blob.isSub=f;
+ blob.secondVal=i; blob.secondShift=0;
+
+ ops.push_back(blob);
+
+ i = ops.size();
+
+ munchLeadingZeros(t);
+
+ if(t.length()==0)
+ return i;
+
+ if(t.c_str()[0]!='P') {
+ g=2;
+ for(int p=0; p<t.length(); p++) {
+ bool isP=(t.c_str()[p]=='P');
+ bool isN=(t.c_str()[p]=='N');
+
+ if(isP)
+ t.replace(p, 1, "N");
+ if(isN)
+ t.replace(p, 1, "P");
+ }
+ }
+
+ int j = lefevre(t, ops);
+
+ int trail=countTrailingZeros(u);
+ blob.secondVal=i; blob.secondShift=trail;
+
+ trail=countTrailingZeros(t);
+ blob.firstVal=j; blob.firstShift=trail;
+
+ switch(g) {
+ case 0:
+ blob.isSub=false; // first + second
+ break;
+ case 1:
+ blob.isSub=true; // first - second
+ break;
+ case 2:
+ blob.isSub=true; // second - first
+ int tmpval, tmpshift;
+ tmpval=blob.firstVal;
+ tmpshift=blob.firstShift;
+ blob.firstVal=blob.secondVal;
+ blob.firstShift=blob.secondShift;
+ blob.secondVal=tmpval;
+ blob.secondShift=tmpshift;
+ break;
+ //assert
+ }
+
+ ops.push_back(blob);
+ return ops.size();
+}
+
+SDOperand ISel::BuildConstmulSequence(SDOperand N) {
+ //FIXME: we should shortcut this stuff for multiplies by 2^n+1
+ // in particular, *3 is nicer as *2+1, not *4-1
+ int64_t constant=cast<ConstantSDNode>(N.getOperand(1))->getValue();
+
+ bool flippedSign;
+ unsigned preliminaryShift=0;
+
+ assert(constant > 0 && "erk, don't multiply by zero or negative nums\n");
+
+ // first, we make the constant to multiply by positive
+ if(constant<0) {
+ constant=-constant;
+ flippedSign=true;
+ } else {
+ flippedSign=false;
+ }
+
+ // next, we make it odd.
+ for(; (constant%2==0); preliminaryShift++)
+ constant>>=1;
+
+ //OK, we have a positive, odd number of 64 bits or less. Convert it
+ //to a binary string, constantString[0] is the LSB
+ char constantString[65];
+ for(int i=0; i<64; i++)
+ constantString[i]='0'+((constant>>i)&0x1);
+ constantString[64]=0;
+
+ // now, Booth encode it
+ std::string boothEncodedString;
+ boothEncode(constantString, boothEncodedString);
+
+ std::vector<struct shiftaddblob> ops;
+ // do the transformation, filling out 'ops'
+ lefevre(boothEncodedString, ops);
+
+ SDOperand results[ops.size()]; // temporary results (of adds/subs of shifts)
+
+ // now turn 'ops' into DAG bits
+ for(int i=0; i<ops.size(); i++) {
+ SDOperand amt = ISelDAG->getConstant(ops[i].firstShift, MVT::i64);
+ SDOperand val = (ops[i].firstVal == 0) ? N.getOperand(0) :
+ results[ops[i].firstVal-1];
+ SDOperand left = ISelDAG->getNode(ISD::SHL, MVT::i64, val, amt);
+ amt = ISelDAG->getConstant(ops[i].secondShift, MVT::i64);
+ val = (ops[i].secondVal == 0) ? N.getOperand(0) :
+ results[ops[i].secondVal-1];
+ SDOperand right = ISelDAG->getNode(ISD::SHL, MVT::i64, val, amt);
+ if(ops[i].isSub)
+ results[i] = ISelDAG->getNode(ISD::SUB, MVT::i64, left, right);
+ else
+ results[i] = ISelDAG->getNode(ISD::ADD, MVT::i64, left, right);
+ }
+
+ // don't forget flippedSign and preliminaryShift!
+ SDOperand finalresult;
+ if(preliminaryShift) {
+ SDOperand finalshift = ISelDAG->getConstant(preliminaryShift, MVT::i64);
+ finalresult = ISelDAG->getNode(ISD::SHL, MVT::i64,
+ results[ops.size()-1], finalshift);
+ } else { // there was no preliminary divide-by-power-of-2 required
+ finalresult = results[ops.size()-1];
+ }
+
+ return finalresult;
}
/// ExactLog2 - This function solves for (Val == 1 << (N-1)) and returns N. It
}
case ISD::MUL: {
- Tmp1 = SelectExpr(N.getOperand(0));
- Tmp2 = SelectExpr(N.getOperand(1));
if(DestType != MVT::f64) { // TODO: speed!
- // boring old integer multiply with xma
- unsigned TempFR1=MakeReg(MVT::f64);
- unsigned TempFR2=MakeReg(MVT::f64);
- unsigned TempFR3=MakeReg(MVT::f64);
- BuildMI(BB, IA64::SETFSIG, 1, TempFR1).addReg(Tmp1);
- BuildMI(BB, IA64::SETFSIG, 1, TempFR2).addReg(Tmp2);
- BuildMI(BB, IA64::XMAL, 1, TempFR3).addReg(TempFR1).addReg(TempFR2)
- .addReg(IA64::F0);
- BuildMI(BB, IA64::GETFSIG, 1, Result).addReg(TempFR3);
+ if(N.getOperand(1).getOpcode() != ISD::Constant) { // if not a const mul
+ // boring old integer multiply with xma
+ Tmp1 = SelectExpr(N.getOperand(0));
+ Tmp2 = SelectExpr(N.getOperand(1));
+
+ unsigned TempFR1=MakeReg(MVT::f64);
+ unsigned TempFR2=MakeReg(MVT::f64);
+ unsigned TempFR3=MakeReg(MVT::f64);
+ BuildMI(BB, IA64::SETFSIG, 1, TempFR1).addReg(Tmp1);
+ BuildMI(BB, IA64::SETFSIG, 1, TempFR2).addReg(Tmp2);
+ BuildMI(BB, IA64::XMAL, 1, TempFR3).addReg(TempFR1).addReg(TempFR2)
+ .addReg(IA64::F0);
+ BuildMI(BB, IA64::GETFSIG, 1, Result).addReg(TempFR3);
+ return Result; // early exit
+ } else { // we are multiplying by an integer constant! yay
+ return Reg = SelectExpr(BuildConstmulSequence(N)); // avert your eyes!
+ }
}
- else // floating point multiply
+ else { // floating point multiply
+ Tmp1 = SelectExpr(N.getOperand(0));
+ Tmp2 = SelectExpr(N.getOperand(1));
BuildMI(BB, IA64::FMPY, 2, Result).addReg(Tmp1).addReg(Tmp2);
- return Result;
+ return Result;
+ }
}
case ISD::SUB: {
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