READ_LATENCY patch for review.
Sample of use:
class RegConstraint<string C> {
string Constraints = C;
}
// AI_orr - Defines a (op r, r) pattern.
class AI_orr<string opc, SDNode opnode>
: AI<(ops GPR:$dst, GPR:$a, GPR:$b),
!strconcat(opc, " $dst, $a, $b"),
[(set GPR:$dst, (opnode GPR:$a, GPR:$b))]>,
RegConstraint<"$a lat 2">;
Lauro
2007/1/26, Evan Cheng <[EMAIL PROTECTED]>:
On Jan 26, 2007, at 1:07 PM, Lauro Ramos Venancio wrote:
>> The facility does that have to be that general. There are 4 cycles
>> between every two instructions. See LiveIntervalAnalysis:
>>
>> struct InstrSlots {
>> enum {
>> LOAD = 0,
>> USE = 1,
>> DEF = 2,
>> STORE = 3,
>> NUM = 4
>> };
>> };
>>
>> We can restrict the constraint range to 1 - 3. This ensures the last
>> use is always the kill while retaining its flexibility.
>>
>> Evan
>
> I will try to implement this. Do you have any suggestion for
> constraint name and syntax?
I don't have any great ideas. Perhaps READ_LATENCY for constraint and
something like
$src +lat 2
for syntax?
Feel free to choose something else if you have better ideas.
Thanks,
Evan
>
> Lauro
Index: include/llvm/Target/TargetInstrInfo.h
===================================================================
RCS file: /var/cvs/llvm/llvm/include/llvm/Target/TargetInstrInfo.h,v
retrieving revision 1.111
diff -u -r1.111 TargetInstrInfo.h
--- include/llvm/Target/TargetInstrInfo.h 26 Jan 2007 14:34:51 -0000 1.111
+++ include/llvm/Target/TargetInstrInfo.h 5 Feb 2007 21:05:56 -0000
@@ -94,9 +94,10 @@
const unsigned M_PREDICATE_OPERAND = 1 << 1;
namespace TOI {
- // Operand constraints: only "tied_to" for now.
+ // Operand constraints: only "tied_to" and read_latency for now.
enum OperandConstraint {
- TIED_TO = 0 // Must be allocated the same register as.
+ TIED_TO = 0, // Must be allocated the same register as.
+ READ_LATENCY // Number of cycles needed for read operand.
};
}
Index: lib/CodeGen/LiveIntervalAnalysis.cpp
===================================================================
RCS file: /var/cvs/llvm/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp,v
retrieving revision 1.204
diff -u -r1.204 LiveIntervalAnalysis.cpp
--- lib/CodeGen/LiveIntervalAnalysis.cpp 19 Dec 2006 22:41:21 -0000 1.204
+++ lib/CodeGen/LiveIntervalAnalysis.cpp 5 Feb 2007 21:05:57 -0000
@@ -441,6 +441,24 @@
DOUT << "\t\tregister: "; DEBUG(printRegName(interval.reg));
LiveVariables::VarInfo& vi = lv_->getVarInfo(interval.reg);
+ // For each kill, get the greatest read latency of the virtual register.
+ std::vector<char> ReadLatency(vi.Kills.size());
+ for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i){
+ const TargetInstrDescriptor *instrDescriptor =
+ vi.Kills[i]->getInstrDescriptor();
+ ReadLatency[i] = InstrSlots::USE; //default read latency
+ //find the operands that use the virtual register
+ for (unsigned j = 0, f = vi.Kills[i]->getNumOperands(); j != f; ++j){
+ MachineOperand op = vi.Kills[i]->getOperand(j);
+ if (op.isRegister() && op.isUse() && (op.getReg() == interval.reg)) {
+ int read_latency =
+ instrDescriptor->getOperandConstraint(j, TOI::READ_LATENCY);
+ if (read_latency != -1 && read_latency > ReadLatency[i])
+ ReadLatency[i] = (char) read_latency;
+ }
+ }
+ }
+
// Virtual registers may be defined multiple times (due to phi
// elimination and 2-addr elimination). Much of what we do only has to be
// done once for the vreg. We use an empty interval to detect the first
@@ -467,7 +485,7 @@
// FIXME: what about dead vars?
unsigned killIdx;
if (vi.Kills[0] != mi)
- killIdx = getUseIndex(getInstructionIndex(vi.Kills[0]))+1;
+ killIdx = getInstructionIndex(vi.Kills[0]) + ReadLatency[0] + 1;
else
killIdx = defIndex+1;
@@ -514,7 +532,7 @@
for (unsigned i = 0, e = vi.Kills.size(); i != e; ++i) {
MachineInstr *Kill = vi.Kills[i];
LiveRange LR(getMBBStartIdx(Kill->getParent()),
- getUseIndex(getInstructionIndex(Kill))+1,
+ getInstructionIndex(Kill)+ ReadLatency[i] + 1,
ValNum);
interval.addRange(LR);
DOUT << " +" << LR;
@@ -574,7 +592,7 @@
// Remove the old range that we now know has an incorrect number.
MachineInstr *Killer = vi.Kills[0];
unsigned Start = getMBBStartIdx(Killer->getParent());
- unsigned End = getUseIndex(getInstructionIndex(Killer))+1;
+ unsigned End = getInstructionIndex(Killer) + ReadLatency[0] + 1;
DOUT << "Removing [" << Start << "," << End << "] from: ";
interval.print(DOUT, mri_); DOUT << "\n";
interval.removeRange(Start, End);
Index: lib/CodeGen/RegAllocLocal.cpp
===================================================================
RCS file: /var/cvs/llvm/llvm/lib/CodeGen/RegAllocLocal.cpp,v
retrieving revision 1.100
diff -u -r1.100 RegAllocLocal.cpp
--- lib/CodeGen/RegAllocLocal.cpp 1 Feb 2007 05:31:50 -0000 1.100
+++ lib/CodeGen/RegAllocLocal.cpp 5 Feb 2007 21:05:57 -0000
@@ -567,10 +567,20 @@
}
SmallVector<unsigned, 8> Kills;
+ SmallVector<char, 8> ReadLatency;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
- if (MO.isRegister() && MO.isKill())
+ if (MO.isRegister() && MO.isKill()){
Kills.push_back(MO.getReg());
+ int read_latency = 1;
+ //we can't call getOperandConstraint on a implicit MO
+ if (!MO.isImplicit()) {
+ read_latency = TID.getOperandConstraint(i,TOI::READ_LATENCY);
+ if (read_latency == -1)
+ read_latency = 1;
+ }
+ ReadLatency.push_back((char)read_latency);
+ }
}
// Get the used operands into registers. This has the potential to spill
@@ -591,6 +601,7 @@
// value, freeing the register being used, so it doesn't need to be
// spilled to memory.
//
+ SmallVector<unsigned, 8> PostponedRegRemove;
for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
unsigned VirtReg = Kills[i];
unsigned PhysReg = VirtReg;
@@ -606,16 +617,21 @@
}
if (PhysReg) {
- DOUT << " Last use of " << RegInfo->getName(PhysReg)
- << "[%reg" << VirtReg <<"], removing it from live set\n";
- removePhysReg(PhysReg);
- for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
- *AliasSet; ++AliasSet) {
- if (PhysRegsUsed[*AliasSet] != -2) {
- DOUT << " Last use of "
- << RegInfo->getName(*AliasSet)
- << "[%reg" << VirtReg <<"], removing it from live set\n";
- removePhysReg(*AliasSet);
+ if (ReadLatency[i] > 1) {
+ //postpone the reg remove from live set.
+ PostponedRegRemove.push_back(PhysReg);
+ } else {
+ DOUT << " Last use of " << RegInfo->getName(PhysReg)
+ << "[%reg" << VirtReg <<"], removing it from live set\n";
+ removePhysReg(PhysReg);
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
+ *AliasSet; ++AliasSet) {
+ if (PhysRegsUsed[*AliasSet] != -2) {
+ DOUT << " Last use of "
+ << RegInfo->getName(*AliasSet)
+ << "[%reg" << VirtReg <<"], removing it from live set\n";
+ removePhysReg(*AliasSet);
+ }
}
}
}
@@ -731,7 +747,24 @@
}
}
}
-
+
+ //Do postponed reg removes from live set
+ for (unsigned i = 0, e = PostponedRegRemove.size(); i != e; ++i) {
+ DOUT << " Last use of " << RegInfo->getName(PostponedRegRemove[i])
+ <<", removing it from live set (postponed)\n";
+ removePhysReg(PostponedRegRemove[i]);
+ for (const unsigned *AliasSet =
+ RegInfo->getAliasSet(PostponedRegRemove[i]);
+ *AliasSet; ++AliasSet) {
+ if (PhysRegsUsed[*AliasSet] != -2) {
+ DOUT << " Last use of "
+ << RegInfo->getName(*AliasSet)
+ <<", removing it from live set (postponed)\n";
+ removePhysReg(*AliasSet);
+ }
+ }
+ }
+
// Finally, if this is a noop copy instruction, zap it.
unsigned SrcReg, DstReg;
if (TII.isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg) {
Index: utils/TableGen/CodeGenTarget.cpp
===================================================================
RCS file: /var/cvs/llvm/llvm/utils/TableGen/CodeGenTarget.cpp,v
retrieving revision 1.82
diff -u -r1.82 CodeGenTarget.cpp
--- utils/TableGen/CodeGenTarget.cpp 26 Jan 2007 17:29:20 -0000 1.82
+++ utils/TableGen/CodeGenTarget.cpp 5 Feb 2007 21:06:00 -0000
@@ -20,6 +20,7 @@
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Streams.h"
+#include "llvm/Target/TargetInstrInfo.h"
#include <set>
#include <algorithm>
using namespace llvm;
@@ -284,38 +285,61 @@
static void ParseConstraint(const std::string &CStr, CodeGenInstruction *I) {
- // FIXME: Only supports TIED_TO for now.
- std::string::size_type pos = CStr.find_first_of('=');
- assert(pos != std::string::npos && "Unrecognized constraint");
- std::string Name = CStr.substr(0, pos);
-
- // TIED_TO: $src1 = $dst
- std::string::size_type wpos = Name.find_first_of(" \t");
- if (wpos == std::string::npos)
- throw "Illegal format for tied-to constraint: '" + CStr + "'";
- std::string DestOpName = Name.substr(0, wpos);
- std::pair<unsigned,unsigned> DestOp = I->ParseOperandName(DestOpName, false);
-
- Name = CStr.substr(pos+1);
- wpos = Name.find_first_not_of(" \t");
- if (wpos == std::string::npos)
- throw "Illegal format for tied-to constraint: '" + CStr + "'";
-
- std::pair<unsigned,unsigned> SrcOp =
- I->ParseOperandName(Name.substr(wpos), false);
- if (SrcOp > DestOp)
- throw "Illegal tied-to operand constraint '" + CStr + "'";
-
-
- unsigned FlatOpNo = I->getFlattenedOperandNumber(SrcOp);
+ std::pair<unsigned,unsigned> Operand;
+ unsigned ConstraintValue;
+ TOI::OperandConstraint Constraint;
+ std::string::size_type pos;
+
+ if ((pos = CStr.find_first_of('=')) != std::string::npos) {
+ //TIED_TO Constraint
+ Constraint = TOI::TIED_TO;
+ std::string Name = CStr.substr(0, pos);
+ // TIED_TO: $src1 = $dst
+ std::string::size_type wpos = Name.find_first_of(" \t");
+ if (wpos == std::string::npos)
+ throw "Illegal format for tied-to constraint: '" + CStr + "'";
+ std::string DestOpName = Name.substr(0, wpos);
+ Operand = I->ParseOperandName(DestOpName, false);
+
+ Name = CStr.substr(pos+1);
+ wpos = Name.find_first_not_of(" \t");
+ if (wpos == std::string::npos)
+ throw "Illegal format for tied-to constraint: '" + CStr + "'";
+
+ std::pair<unsigned,unsigned> SrcOp =
+ I->ParseOperandName(Name.substr(wpos), false);
+ if (SrcOp > Operand)
+ throw "Illegal tied-to operand constraint '" + CStr + "'";
+ ConstraintValue = I->getFlattenedOperandNumber(SrcOp);
+
+ } else if ((pos = CStr.find("lat")) != std::string::npos) {
+ //READ_LATENCY Constraint
+ Constraint = TOI::READ_LATENCY;
+
+ //get read latency operand
+ std::string Name = CStr.substr(0, pos);
+ std::string::size_type wpos = Name.find_first_of(" \t");
+ if (wpos == std::string::npos)
+ throw "Illegal format for read-latency constraint: '" + CStr + "'";
+ std::string OpName = Name.substr(0, wpos);
+ Operand = I->ParseOperandName(OpName, false);
+
+ //get read latancy value
+ Name = CStr.substr(pos+3);
+ sscanf(Name.c_str(),"%u",&ConstraintValue);
+ if (ConstraintValue <= 0 || ConstraintValue > 3)
+ throw "Invalid read latency value: '" + CStr + "'";
+ } else {
+ throw "Unrecognized constraint";
+ }
+
// Build the string for the operand.
- std::string OpConstraint =
- "((" + utostr(FlatOpNo) + " << 16) | (1 << TOI::TIED_TO))";
+ std::string OpConstraint ="((" + utostr(ConstraintValue) + " << " +
+ utostr(16 + Constraint * 4) + ") | (1 << " + utostr(Constraint) +"))";
-
- if (!I->OperandList[DestOp.first].Constraints[DestOp.second].empty())
- throw "Operand '" + DestOpName + "' cannot have multiple constraints!";
- I->OperandList[DestOp.first].Constraints[DestOp.second] = OpConstraint;
+ if (!I->OperandList[Operand.first].Constraints[Operand.second].empty())
+ throw "Operands cannot have multiple constraints.";
+ I->OperandList[Operand.first].Constraints[Operand.second] = OpConstraint;
}
static void ParseConstraints(const std::string &CStr, CodeGenInstruction *I) {
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