This new class provides support for platform specific "features". The intent

is to manage processor specific attributes from the command line.  See examples
of use in llc/lli and PowerPCTargetSubtarget.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23191 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/SubtargetFeature.cpp

@@ -0,0 +1,173 @@
+//===- SubtargetFeature.cpp - CPU characteristics Implementation ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Jim Laskey and is distributed under the 
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SubtargetFeature interface.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Target/SubtargetFeature.h"
+
+#include <string>
+#include <algorithm>
+#include <vector>
+#include <cassert>
+
+
+using namespace llvm;
+
+/// Splits a string of comma separated items in to a vector of strings.
+void SubtargetFeatures::Split(std::vector<std::string> &V,
+                              const std::string &S) {
+  // Start at beginning of string.
+  size_t Pos = 0;
+  while (true) {
+    // Find the next comma
+    size_t Comma = S.find(',', Pos);
+    // If no comma found then the the rest of the string is used
+    if (Comma == std::string::npos) {
+      // Add string to vector
+      V.push_back(S.substr(Pos));
+      break;
+    }
+    // Otherwise add substring to vector
+    V.push_back(S.substr(Pos, Comma - Pos));
+    // Advance to next item
+    Pos = Comma + 1;
+  }
+}
+
+/// Join a vector of strings to a string with a comma separating each element.
+std::string SubtargetFeatures::Join(const std::vector<std::string> &V) {
+  // Start with empty string.
+  std::string Result;
+  // If the vector is not empty 
+  if (!V.empty()) {
+    // Start with the CPU feature
+    Result = V[0];
+    // For each successive feature
+    for (size_t i = 1; i < V.size(); i++) {
+      // Add a comma
+      Result += ",";
+      // Add the feature
+      Result += V[i];
+    }
+  }
+  // Return the features string 
+  return Result;
+}
+
+/// Convert a string to lowercase.
+std::string SubtargetFeatures::toLower(const std::string &S) {
+  // Copy the string
+  std::string Result = S;
+  // For each character in string
+  for (size_t i = 0; i < Result.size(); i++) {
+    // Convert character to lowercase
+    Result[i] = std::tolower(Result[i]);
+  }
+  // Return the lowercased string
+  return Result;
+}
+
+/// Adding features.
+void SubtargetFeatures::AddFeature(const std::string &String,
+                                   bool IsEnabled) {
+  // Don't add empty features
+  if (!String.empty()) {
+    // Convert to lowercase, prepend flag and add to vector
+    Features.push_back(PrependFlag(toLower(String), IsEnabled));
+  }
+}
+
+/// Find item in array using binary search.
+const SubtargetFeatureKV *
+SubtargetFeatures::Find(const std::string &S,
+                        const SubtargetFeatureKV *A, size_t L) {
+  // Determine the end of the array
+  const SubtargetFeatureKV *Hi = A + L;
+  // Binary search the array
+  const SubtargetFeatureKV *F = std::lower_bound(A, Hi, S);
+  // If not found then return NULL
+  if (F == Hi || std::string(F->Key) != S) return NULL;
+  // Return the found array item
+  return F;
+}
+
+/// Parse feature string for quick usage.
+uint32_t SubtargetFeatures::Parse(const std::string &String,
+                                  const std::string &DefaultCPU,
+                                  const SubtargetFeatureKV *CPUTable,
+                                  size_t CPUTableSize,
+                                  const SubtargetFeatureKV *FeatureTable,
+                                  size_t FeatureTableSize) {
+  assert(CPUTable && "missing CPU table");
+  assert(FeatureTable && "missing features table");
+#ifndef NDEBUG
+  for (size_t i = 1; i < CPUTableSize; i++) {
+    assert(strcmp(CPUTable[i - 1].Key, CPUTable[i].Key) < 0 &&
+           "CPU table is not sorted");
+  }
+  for (size_t i = 1; i < FeatureTableSize; i++) {
+    assert(strcmp(FeatureTable[i - 1].Key, FeatureTable[i].Key) < 0 &&
+          "CPU features table is not sorted");
+  }
+#endif
+  std::vector<std::string> Features;    // Subtarget features as a vector
+  uint32_t Bits = 0;                    // Resulting bits
+  // Split up features
+  Split(Features, String);
+  // Check if default is needed
+  if (Features[0].empty()) Features[0] = DefaultCPU;
+  // Find CPU entry
+  const SubtargetFeatureKV *CPUEntry =
+                            Find(Features[0], CPUTable, CPUTableSize);
+  // If there is a match
+  if (CPUEntry) {
+    // Set base feature bits
+    Bits = CPUEntry->Value;
+  } else {
+    std::cerr << Features[0]
+              << " is not a recognized processor for this target"
+              << " (ignoring processor)"
+              << "\n";
+  }
+  // Iterate through each feature
+  for (size_t i = 1; i < Features.size(); i++) {
+    // Get next feature
+    const std::string &Feature = Features[i];
+    // Find feature in table.
+    const SubtargetFeatureKV *FeatureEntry =
+                       Find(StripFlag(Feature), FeatureTable, FeatureTableSize);
+    // If there is a match
+    if (FeatureEntry) {
+      // Enable/disable feature in bits
+      if (isEnabled(Feature)) Bits |=  FeatureEntry->Value;
+      else                    Bits &= ~FeatureEntry->Value;
+    } else {
+      std::cerr << Feature
+                << " is not a recognized feature for this target"
+                << " (ignoring feature)"
+                << "\n";
+    }
+  }
+  return Bits;
+}
+
+/// Print feature string.
+void SubtargetFeatures::print(std::ostream &OS) const {
+  for (size_t i = 0; i < Features.size(); i++) {
+    OS << Features[i] << "  ";
+  }
+  OS << "\n";
+}
+
+/// Dump feature info.
+void SubtargetFeatures::dump() const {
+  print(std::cerr);
+}