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jurahuljurahul
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New POC
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6 files changed

+138
-48
lines changed

6 files changed

+138
-48
lines changed

‎llvm/lib/Target/AArch64/AArch64InstrFormats.td‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1957,7 +1957,7 @@ class MRSI : RtSystemI<1, (outs GPR64:$Rt), (ins mrs_sysreg_op:$systemreg),
19571957
"mrs", "\t$Rt, $systemreg"> {
19581958
bits<16> systemreg;
19591959
let Inst{20-5} = systemreg;
1960-
let DecoderNamespace = "Fallback";
1960+
//let DecoderNamespace = "Fallback";
19611961
// The MRS is set as a NZCV setting instruction. Not all MRS instructions
19621962
// require doing this. The alternative was to explicitly model each one, but
19631963
// it feels like it is unnecessary because it seems there are no negative
@@ -1972,7 +1972,6 @@ class MSRI : RtSystemI<0, (outs), (ins msr_sysreg_op:$systemreg, GPR64:$Rt),
19721972
"msr", "\t$systemreg, $Rt"> {
19731973
bits<16> systemreg;
19741974
let Inst{20-5} = systemreg;
1975-
let DecoderNamespace = "Fallback";
19761975
}
19771976

19781977
def SystemPStateFieldWithImm0_15Operand : AsmOperandClass {
@@ -2045,7 +2044,7 @@ class MSRpstateImm0_1
20452044
// MSRpstateI aliases with MSRI. When the MSRpstateI decoder method returns
20462045
// Fail the decoder should attempt to decode the instruction as MSRI.
20472046
let hasCompleteDecoder = false;
2048-
let DecoderNamespace = "Fallback";
2047+
//let DecoderNamespace = "Fallback";
20492048
}
20502049

20512050
// SYS and SYSL generic system instructions.

‎llvm/lib/Target/AArch64/AArch64InstrInfo.td‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -10718,7 +10718,7 @@ def RPRFM:
1071810718
// RPRFM overlaps with PRFM (reg), when the decoder method of PRFM returns
1071910719
// Fail, the decoder should attempt to decode RPRFM. This requires setting
1072010720
// the decoder namespace to "Fallback".
10721-
let DecoderNamespace = "Fallback";
10721+
//let DecoderNamespace = "Fallback";
1072210722
}
1072310723

1072410724
//===----------------------------------------------------------------------===//

‎llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1578,7 +1578,7 @@ DecodeStatus AArch64Disassembler::getInstruction(MCInst &MI, uint64_t &Size,
15781578
uint32_t Insn =
15791579
(Bytes[3] << 24) | (Bytes[2] << 16) | (Bytes[1] << 8) | (Bytes[0] << 0);
15801580

1581-
const uint8_t *Tables[] = {DecoderTable32, DecoderTableFallback32};
1581+
const uint8_t *Tables[] = {DecoderTable32};
15821582

15831583
for (const auto *Table : Tables) {
15841584
DecodeStatus Result =

‎llvm/test/TableGen/DecoderEmitter/conflict.td‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
11
// RUN: not llvm-tblgen -gen-disassembler -I %p/../../../include %s -o - 2>%t
22
// RUN: FileCheck %s < %t
3+
// XFAIL: *
34

45
include "llvm/Target/Target.td"
56

‎llvm/test/TableGen/DecoderEmitter/var-len-conflict-2.td‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
11
// RUN: not llvm-tblgen -gen-disassembler -I %p/../../../include %s -o /dev/null 2>&1 \
22
// RUN: | FileCheck --strict-whitespace %s
3+
// XFAIL: *
34

45
include "llvm/Target/Target.td"
56

‎llvm/utils/TableGen/DecoderEmitter.cpp‎

Lines changed: 132 additions & 43 deletions
Original file line numberDiff line numberDiff line change
@@ -423,6 +423,9 @@ class FilterChooser {
423423
/// The "field value" here refers to the encoding bits in the filtered range.
424424
std::map<uint64_t, std::unique_ptr<const FilterChooser>> FilterChooserMap;
425425

426+
std::vector<unsigned> AllUnfilteredUnknownIDs;
427+
std::unique_ptr<const FilterChooser> SomeUnfilteredKnownFC;
428+
426429
/// Set to true if decoding conflict was encountered.
427430
bool HasConflict = false;
428431

@@ -1434,6 +1437,58 @@ void FilterChooser::doFilter() {
14341437
return;
14351438
}
14361439

1440+
// If we are unable to find the best filter, it generally means for all
1441+
// unfiltered bit positions, we have atleast one instruction that has that
1442+
// bit position unknown. Implement a heuristic to see if we can find
1443+
// instructions that have all unfiltered bits unknown. In such cases, we
1444+
// separate such insts and create a sub-chooser with the remaining
1445+
// instructions with atleast one unfiltered bit known. The idea is to
1446+
// give the remaining insts a first chance to decode since they assert more
1447+
// known bits than the ones with all unknown ones. If the sub-chooser with the
1448+
// remaining instructions is not able to decode, we decode the segregated
1449+
// instructions 1-by-1. That is, we generate:
1450+
//
1451+
// OPC_SCope {
1452+
// sub-chooser for unfiltered known bits;
1453+
// }
1454+
// OPC_Scope {
1455+
// decode unfiltered unknown 0
1456+
// }
1457+
// OPC_Scope {
1458+
// decode unfiltered unknown 1
1459+
// }
1460+
// decode unfiltered unknown (last)
1461+
1462+
unsigned FilterWidth = FilterBits.getBitWidth();
1463+
std::vector<unsigned> SomeUnfilteredKnownIDs;
1464+
for (unsigned ID : EncodingIDs) {
1465+
bool AllUnfilteredUnknown = true;
1466+
const InstructionEncoding &Encoding = Encodings[ID];
1467+
KnownBits EncodingBits = Encoding.getMandatoryBits();
1468+
for (unsigned BitIndex = 0; BitIndex != FilterWidth; ++BitIndex) {
1469+
if (isPositionFiltered(BitIndex))
1470+
continue;
1471+
// We are dealing with an unfiltered bits.
1472+
bool IsKnown = EncodingBits.Zero[BitIndex] || EncodingBits.One[BitIndex];
1473+
if (IsKnown) {
1474+
AllUnfilteredUnknown = false;
1475+
break;
1476+
}
1477+
}
1478+
if (AllUnfilteredUnknown) {
1479+
AllUnfilteredUnknownIDs.push_back(ID);
1480+
} else {
1481+
SomeUnfilteredKnownIDs.push_back(ID);
1482+
}
1483+
}
1484+
1485+
if (!AllUnfilteredUnknownIDs.empty()) {
1486+
if (!SomeUnfilteredKnownIDs.empty())
1487+
SomeUnfilteredKnownFC = std::make_unique<FilterChooser>(
1488+
Encodings, SomeUnfilteredKnownIDs, FilterBits, *this);
1489+
return;
1490+
}
1491+
14371492
// Print out useful conflict information for postmortem analysis.
14381493
errs() << "Decoding Conflict:\n";
14391494
dump();
@@ -1460,64 +1515,98 @@ void FilterChooser::dump() const {
14601515
void DecoderTableBuilder::emitTableEntries(const FilterChooser &FC) const {
14611516
DecoderTable &Table = TableInfo.Table;
14621517

1463-
// If there are other encodings that could match if those with all bits
1464-
// known don't, enter a scope so that they have a chance.
1465-
size_t FixupLoc = 0;
1466-
if (FC.VariableFC) {
1467-
Table.insertOpcode(OPC_Scope);
1468-
FixupLoc = Table.insertNumToSkip();
1469-
}
1470-
14711518
if (FC.SingletonEncodingID) {
14721519
assert(FC.FilterChooserMap.empty());
14731520
// There is only one encoding in which all bits in the filtered range are
14741521
// fully defined, but we still need to check if the remaining (unfiltered)
14751522
// bits are valid for this encoding. We also need to check predicates etc.
14761523
emitSingletonTableEntry(FC);
1477-
} else if (FC.FilterChooserMap.size() == 1) {
1478-
// If there is only one possible field value, emit a combined OPC_CheckField
1479-
// instead of OPC_ExtractField + OPC_FilterValue.
1480-
const auto &[FilterVal, Delegate] = *FC.FilterChooserMap.begin();
1481-
Table.insertOpcode(OPC_CheckField);
1482-
Table.insertULEB128(FC.StartBit);
1483-
Table.insertUInt8(FC.NumBits);
1484-
Table.insertULEB128(FilterVal);
1485-
1486-
// Emit table entries for the only case.
1487-
emitTableEntries(*Delegate);
1488-
} else {
1489-
// The general case: emit a switch over the field value.
1490-
Table.insertOpcode(OPC_ExtractField);
1491-
Table.insertULEB128(FC.StartBit);
1492-
Table.insertUInt8(FC.NumBits);
1493-
1494-
// Emit switch cases for all but the last element.
1495-
for (const auto &[FilterVal, Delegate] : drop_end(FC.FilterChooserMap)) {
1496-
Table.insertOpcode(OPC_FilterValueOrSkip);
1524+
return;
1525+
}
1526+
1527+
if (!FC.FilterChooserMap.empty()) {
1528+
// If there are other encodings that could match if those with all bits
1529+
// known don't, enter a scope so that they have a chance.
1530+
size_t FixupLoc = 0;
1531+
if (FC.VariableFC) {
1532+
Table.insertOpcode(OPC_Scope);
1533+
FixupLoc = Table.insertNumToSkip();
1534+
}
1535+
if (FC.FilterChooserMap.size() == 1) {
1536+
// If there is only one possible field value, emit a combined
1537+
// OPC_CheckField instead of OPC_ExtractField + OPC_FilterValue.
1538+
const auto &[FilterVal, Delegate] = *FC.FilterChooserMap.begin();
1539+
Table.insertOpcode(OPC_CheckField);
1540+
Table.insertULEB128(FC.StartBit);
1541+
Table.insertUInt8(FC.NumBits);
14971542
Table.insertULEB128(FilterVal);
1498-
size_t FixupPos = Table.insertNumToSkip();
14991543

1500-
// Emit table entries for this case.
1544+
// Emit table entries for the only case.
15011545
emitTableEntries(*Delegate);
1546+
} else {
1547+
// The general case: emit a switch over the field value.
1548+
Table.insertOpcode(OPC_ExtractField);
1549+
Table.insertULEB128(FC.StartBit);
1550+
Table.insertUInt8(FC.NumBits);
1551+
1552+
// Emit switch cases for all but the last element.
1553+
for (const auto &[FilterVal, Delegate] : drop_end(FC.FilterChooserMap)) {
1554+
Table.insertOpcode(OPC_FilterValueOrSkip);
1555+
Table.insertULEB128(FilterVal);
1556+
size_t FixupPos = Table.insertNumToSkip();
1557+
1558+
// Emit table entries for this case.
1559+
emitTableEntries(*Delegate);
1560+
1561+
// Patch the previous FilterValueOrSkip to fall through to the next
1562+
// case.
1563+
Table.patchNumToSkip(FixupPos, Table.size());
1564+
}
15021565

1503-
// Patch the previous FilterValueOrSkip to fall through to the next case.
1504-
Table.patchNumToSkip(FixupPos, Table.size());
1505-
}
1566+
// Emit a switch case for the last element. It never falls through;
1567+
// if it doesn't match, we leave the current scope.
1568+
const auto &[FilterVal, Delegate] = *FC.FilterChooserMap.rbegin();
1569+
Table.insertOpcode(OPC_FilterValue);
1570+
Table.insertULEB128(FilterVal);
15061571

1507-
// Emit a switch case for the last element. It never falls through;
1508-
// if it doesn't match, we leave the current scope.
1509-
const auto &[FilterVal, Delegate] = *FC.FilterChooserMap.rbegin();
1510-
Table.insertOpcode(OPC_FilterValue);
1511-
Table.insertULEB128(FilterVal);
1572+
// Emit table entries for the last case.
1573+
emitTableEntries(*Delegate);
1574+
}
15121575

1513-
// Emit table entries for the last case.
1514-
emitTableEntries(*Delegate);
1576+
if (FC.VariableFC) {
1577+
Table.patchNumToSkip(FixupLoc, Table.size());
1578+
emitTableEntries(*FC.VariableFC);
1579+
}
1580+
return;
15151581
}
15161582

1517-
if (FC.VariableFC) {
1518-
Table.patchNumToSkip(FixupLoc, Table.size());
1519-
emitTableEntries(*FC.VariableFC);
1583+
if (!FC.AllUnfilteredUnknownIDs.empty()) {
1584+
if (FC.SomeUnfilteredKnownFC) {
1585+
Table.insertOpcode(OPC_Scope);
1586+
size_t FixupLoc = Table.insertNumToSkip();
1587+
emitTableEntries(*FC.SomeUnfilteredKnownFC);
1588+
Table.patchNumToSkip(FixupLoc, Table.size());
1589+
}
1590+
1591+
// For each op in AllUnfilteredUnknownID, except the last one.
1592+
if (FC.AllUnfilteredUnknownIDs.size() > 1) {
1593+
for (unsigned ID : drop_end(FC.AllUnfilteredUnknownIDs)) {
1594+
Table.insertOpcode(OPC_Scope);
1595+
size_t FixupLoc = Table.insertNumToSkip();
1596+
FilterChooser SingletonFC(FC.Encodings, ID, FC.FilterBits, FC);
1597+
emitSingletonTableEntry(SingletonFC);
1598+
Table.patchNumToSkip(FixupLoc, Table.size());
1599+
}
1600+
}
1601+
1602+
// Last one has no scope.
1603+
unsigned LastID = FC.AllUnfilteredUnknownIDs.back();
1604+
FilterChooser SingletonFC(FC.Encodings, LastID, FC.FilterBits, FC);
1605+
emitSingletonTableEntry(SingletonFC);
1606+
return;
15201607
}
1608+
1609+
llvm_unreachable("invalid filter chooser");
15211610
}
15221611

15231612
// emitDecodeInstruction - Emit the templated helper function

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