[llvm] [RISCV] Reduce size of CSR lookup tables. NFC (PR #121606)
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 3 13:51:49 PST 2025
https://github.com/topperc created https://github.com/llvm/llvm-project/pull/121606
Instead of storing 3 different names in each row of the table, use a separate row for each name and use a flag to indicate what type of name it is. The AltName and DeprecatedName weren't used often enough to justify storing them as a possibility for every register.
This reduces the .rodata says by 27k and reduces the number of dynamic relocations since we now only need 1 lookup by name function. The lookup by name function each contained a ~400 entry table of const char* pointing to constant strings. Each of those requires a dynamic relocation.
>From a7476b4bcb139ec63f469f5d12b7287487439c55 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Fri, 3 Jan 2025 11:37:57 -0800
Subject: [PATCH] [RISCV] Reduce size of CSR lookup tables. NFC
Instead of storing 3 different names in each row of the table, use
a separate row for each name and use a flag to indicate what type
of name it is. The AltName and DeprecatedName aren't used often enough
to justify storing them as a possiblity for every register.
This reduces the .rodata says by 27k and reduces the number of
dynamic relocations since we now only need 1 lookup by name function.
The lookup by name function each contained a ~400 entry table of
const char* pointing to constant strings. Each of those requires a dynamic
relocation.
---
.../Target/RISCV/AsmParser/RISCVAsmParser.cpp | 25 ++++++++-----
.../Target/RISCV/MCTargetDesc/RISCVBaseInfo.h | 8 ++--
.../RISCV/MCTargetDesc/RISCVInstPrinter.cpp | 2 +
llvm/lib/Target/RISCV/RISCVSystemOperands.td | 37 +++++++------------
4 files changed, 36 insertions(+), 36 deletions(-)
diff --git a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
index 4c1fd5aa41e2b7..2205c67c2d21ba 100644
--- a/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
+++ b/llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
@@ -1915,6 +1915,8 @@ ParseStatus RISCVAsmParser::parseCSRSystemRegister(OperandVector &Operands) {
// Accept an immediate representing a named Sys Reg if it satisfies the
// the required features.
for (auto &Reg : Range) {
+ if (Reg.IsAltName || Reg.IsDeprecatedName)
+ continue;
if (Reg.haveRequiredFeatures(STI->getFeatureBits()))
return RISCVOperand::createSysReg(Reg.Name, S, Imm);
}
@@ -1952,22 +1954,27 @@ ParseStatus RISCVAsmParser::parseCSRSystemRegister(OperandVector &Operands) {
return ParseStatus::Failure;
const auto *SysReg = RISCVSysReg::lookupSysRegByName(Identifier);
- if (!SysReg)
- SysReg = RISCVSysReg::lookupSysRegByAltName(Identifier);
- if (!SysReg)
- if ((SysReg = RISCVSysReg::lookupSysRegByDeprecatedName(Identifier)))
- Warning(S, "'" + Identifier + "' is a deprecated alias for '" +
- SysReg->Name + "'");
-
- // Accept a named Sys Reg if the required features are present.
+
if (SysReg) {
+ if (SysReg->IsDeprecatedName) {
+ // Lookup the undeprecated name.
+ auto Range = RISCVSysReg::lookupSysRegByEncoding(SysReg->Encoding);
+ for (auto &Reg : Range) {
+ if (Reg.IsAltName || Reg.IsDeprecatedName)
+ continue;
+ Warning(S, "'" + Identifier + "' is a deprecated alias for '" +
+ Reg.Name + "'");
+ }
+ }
+
+ // Accept a named Sys Reg if the required features are present.
const auto &FeatureBits = getSTI().getFeatureBits();
if (!SysReg->haveRequiredFeatures(FeatureBits)) {
const auto *Feature = llvm::find_if(RISCVFeatureKV, [&](auto Feature) {
return SysReg->FeaturesRequired[Feature.Value];
});
auto ErrorMsg = std::string("system register '") + SysReg->Name + "' ";
- if (SysReg->isRV32Only && FeatureBits[RISCV::Feature64Bit]) {
+ if (SysReg->IsRV32Only && FeatureBits[RISCV::Feature64Bit]) {
ErrorMsg += "is RV32 only";
if (Feature != std::end(RISCVFeatureKV))
ErrorMsg += " and ";
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h
index 7fb5fc7a831308..1c1a8b8009d2ca 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVBaseInfo.h
@@ -454,8 +454,6 @@ int getLoadFPImm(APFloat FPImm);
namespace RISCVSysReg {
struct SysReg {
const char Name[32];
- const char AltName[32];
- const char DeprecatedName[32];
unsigned Encoding;
// FIXME: add these additional fields when needed.
// Privilege Access: Read, Write, Read-Only.
@@ -467,11 +465,13 @@ struct SysReg {
// Register number without the privilege bits.
// unsigned Number;
FeatureBitset FeaturesRequired;
- bool isRV32Only;
+ bool IsRV32Only;
+ bool IsAltName;
+ bool IsDeprecatedName;
bool haveRequiredFeatures(const FeatureBitset &ActiveFeatures) const {
// Not in 32-bit mode.
- if (isRV32Only && ActiveFeatures[RISCV::Feature64Bit])
+ if (IsRV32Only && ActiveFeatures[RISCV::Feature64Bit])
return false;
// No required feature associated with the system register.
if (FeaturesRequired.none())
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVInstPrinter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVInstPrinter.cpp
index d36c0d7238cdc6..d5254719b3839e 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVInstPrinter.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVInstPrinter.cpp
@@ -121,6 +121,8 @@ void RISCVInstPrinter::printCSRSystemRegister(const MCInst *MI, unsigned OpNo,
unsigned Imm = MI->getOperand(OpNo).getImm();
auto Range = RISCVSysReg::lookupSysRegByEncoding(Imm);
for (auto &Reg : Range) {
+ if (Reg.IsAltName || Reg.IsDeprecatedName)
+ continue;
if (Reg.haveRequiredFeatures(STI.getFeatureBits())) {
markup(O, Markup::Register) << Reg.Name;
return;
diff --git a/llvm/lib/Target/RISCV/RISCVSystemOperands.td b/llvm/lib/Target/RISCV/RISCVSystemOperands.td
index 72275daa1b8d16..39853cf13a920c 100644
--- a/llvm/lib/Target/RISCV/RISCVSystemOperands.td
+++ b/llvm/lib/Target/RISCV/RISCVSystemOperands.td
@@ -19,12 +19,6 @@ include "llvm/TableGen/SearchableTable.td"
class SysReg<string name, bits<12> op> {
string Name = name;
- // A maximum of one alias is supported right now.
- string AltName = name;
- // A maximum of one deprecated name is supported right now. Unlike the
- // `AltName` alias, a `DeprecatedName` generates a diagnostic when the name is
- // used to encourage software to migrate away from the name.
- string DeprecatedName = "";
bits<12> Encoding = op;
// FIXME: add these additional fields when needed.
// Privilege Access: Read and Write = 0, 1, 2; Read-Only = 3.
@@ -37,14 +31,16 @@ class SysReg<string name, bits<12> op> {
// bits<6> Number = op{5 - 0};
code FeaturesRequired = [{ {} }];
bit isRV32Only = 0;
+ bit isAltName = 0;
+ bit isDeprecatedName = 0;
}
def SysRegsList : GenericTable {
let FilterClass = "SysReg";
// FIXME: add "ReadWrite", "Mode", "Extra", "Number" fields when needed.
let Fields = [
- "Name", "AltName", "DeprecatedName", "Encoding", "FeaturesRequired",
- "isRV32Only",
+ "Name", "Encoding", "FeaturesRequired",
+ "isRV32Only", "isAltName", "isDeprecatedName"
];
let PrimaryKey = [ "Encoding" ];
@@ -57,16 +53,6 @@ def lookupSysRegByName : SearchIndex {
let Key = [ "Name" ];
}
-def lookupSysRegByAltName : SearchIndex {
- let Table = SysRegsList;
- let Key = [ "AltName" ];
-}
-
-def lookupSysRegByDeprecatedName : SearchIndex {
- let Table = SysRegsList;
- let Key = [ "DeprecatedName" ];
-}
-
// The following CSR encodings match those given in Tables 2.2,
// 2.3, 2.4, 2.5 and 2.6 in the RISC-V Instruction Set Manual
// Volume II: Privileged Architecture.
@@ -123,15 +109,17 @@ def : SysReg<"senvcfg", 0x10A>;
def : SysReg<"sscratch", 0x140>;
def : SysReg<"sepc", 0x141>;
def : SysReg<"scause", 0x142>;
-let DeprecatedName = "sbadaddr" in
def : SysReg<"stval", 0x143>;
+let isDeprecatedName = 1 in
+def : SysReg<"sbadaddr", 0x143>;
def : SysReg<"sip", 0x144>;
//===----------------------------------------------------------------------===//
// Supervisor Protection and Translation
//===----------------------------------------------------------------------===//
-let DeprecatedName = "sptbr" in
def : SysReg<"satp", 0x180>;
+let isDeprecatedName = 1 in
+def : SysReg<"sptbr", 0x180>;
//===----------------------------------------------------------------------===//
// Quality-of-Service(QoS) Identifiers (Ssqosid)
@@ -245,8 +233,9 @@ def : SysReg<"mstatush", 0x310>;
def : SysReg<"mscratch", 0x340>;
def : SysReg<"mepc", 0x341>;
def : SysReg<"mcause", 0x342>;
-let DeprecatedName = "mbadaddr" in
def : SysReg<"mtval", 0x343>;
+let isDeprecatedName = 1 in
+def : SysReg<"mbadaddr", 0x343>;
def : SysReg<"mip", 0x344>;
def : SysReg<"mtinst", 0x34A>;
def : SysReg<"mtval2", 0x34B>;
@@ -298,8 +287,9 @@ foreach i = 3...31 in
//===----------------------------------------------------------------------===//
// Machine Counter Setup
//===----------------------------------------------------------------------===//
-let AltName = "mucounteren" in // Privileged spec v1.9.1 Name
def : SysReg<"mcountinhibit", 0x320>;
+let isAltName = 1 in
+def : SysReg<"mucounteren", 0x320>;
// mhpmevent3-mhpmevent31 at 0x323-0x33F.
foreach i = 3...31 in
@@ -336,8 +326,9 @@ def : SysReg<"dpc", 0x7B1>;
// "dscratch" is an alternative name for "dscratch0" which appeared in earlier
// drafts of the RISC-V debug spec
-let AltName = "dscratch" in
def : SysReg<"dscratch0", 0x7B2>;
+let isAltName = 1 in
+def : SysReg<"dscratch", 0x7B2>;
def : SysReg<"dscratch1", 0x7B3>;
//===----------------------------------------------------------------------===//
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