[RISCV] Add -mtune support

 - The goal of this patch is improve option compatible with RISCV-V GCC,
   -mcpu support on GCC side will sent patch in next few days.

 - -mtune only affect the pipeline model and non-arch/extension related
   target feature, e.g. instruction fusion; in td file it called
   TuneFeatures, which is introduced by X86 back-end[1].

 - -mtune accept all valid option for -mcpu and extra alias processor
   option, e.g. `generic`, `rocket` and `sifive-7-series`, the purpose is
   option compatible with RISCV-V GCC.

 - Processor alias for -mtune will resolve according the current target arch,
   rv32 or rv64, e.g. `rocket` will resolve to `rocket-rv32` or `rocket-rv64`.

 - Interaction between -mcpu and -mtune:
   * -mtune has higher priority than -mcpu for pipeline model and
     TuneFeatures.

[1] https://reviews.llvm.org/D85165

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D89025

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/lib/Support/TargetParser.cpp b/llvm/lib/Support/TargetParser.cpp
index 4d96b34..60d102e 100644
--- a/llvm/lib/Support/TargetParser.cpp
+++ b/llvm/lib/Support/TargetParser.cpp
@@ -253,6 +253,12 @@ bool checkCPUKind(CPUKind Kind, bool IsRV64) {
   return RISCVCPUInfo[static_cast<unsigned>(Kind)].is64Bit() == IsRV64;
 }
 
+bool checkTuneCPUKind(CPUKind Kind, bool IsRV64) {
+  if (Kind == CK_INVALID)
+    return false;
+  return RISCVCPUInfo[static_cast<unsigned>(Kind)].is64Bit() == IsRV64;
+}
+
 CPUKind parseCPUKind(StringRef CPU) {
   return llvm::StringSwitch<CPUKind>(CPU)
 #define PROC(ENUM, NAME, FEATURES, DEFAULT_MARCH) .Case(NAME, CK_##ENUM)
@@ -260,6 +266,22 @@ CPUKind parseCPUKind(StringRef CPU) {
       .Default(CK_INVALID);
 }
 
+StringRef resolveTuneCPUAlias(StringRef TuneCPU, bool IsRV64) {
+  return llvm::StringSwitch<StringRef>(TuneCPU)
+#define PROC_ALIAS(NAME, RV32, RV64) .Case(NAME, IsRV64 ? StringRef(RV64) : StringRef(RV32))
+#include "llvm/Support/RISCVTargetParser.def"
+      .Default(TuneCPU);
+}
+
+CPUKind parseTuneCPUKind(StringRef TuneCPU, bool IsRV64) {
+  TuneCPU = resolveTuneCPUAlias(TuneCPU, IsRV64);
+
+  return llvm::StringSwitch<CPUKind>(TuneCPU)
+#define PROC(ENUM, NAME, FEATURES, DEFAULT_MARCH) .Case(NAME, CK_##ENUM)
+#include "llvm/Support/RISCVTargetParser.def"
+      .Default(CK_INVALID);
+}
+
 StringRef getMArchFromMcpu(StringRef CPU) {
   CPUKind Kind = parseCPUKind(CPU);
   return RISCVCPUInfo[static_cast<unsigned>(Kind)].DefaultMarch;
@@ -272,6 +294,15 @@ void fillValidCPUArchList(SmallVectorImpl<StringRef> &Values, bool IsRV64) {
   }
 }
 
+void fillValidTuneCPUArchList(SmallVectorImpl<StringRef> &Values, bool IsRV64) {
+  for (const auto &C : RISCVCPUInfo) {
+    if (C.Kind != CK_INVALID && IsRV64 == C.is64Bit())
+      Values.emplace_back(C.Name);
+  }
+#define PROC_ALIAS(NAME, RV32, RV64) Values.emplace_back(StringRef(NAME));
+#include "llvm/Support/RISCVTargetParser.def"
+}
+
 // Get all features except standard extension feature
 bool getCPUFeaturesExceptStdExt(CPUKind Kind,
                                 std::vector<StringRef> &Features) {