From 4222d806faae71ecc794cfdaa873817873c2f3d8 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Fri, 4 May 2007 20:38:40 +0000
Subject: Add an "implies" field to features. This indicates that, if the
 current feature is set, then the features in the implied list should be set
 also. The opposite is also enforced: if a feature in the implied list isn't
 set, then the feature that owns that implies list shouldn't be set either.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36756 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/SubtargetFeature.cpp | 51 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

(limited to 'lib/Target/SubtargetFeature.cpp')

diff --git a/lib/Target/SubtargetFeature.cpp b/lib/Target/SubtargetFeature.cpp
index 4669e0fdc3..598f02982b 100644
--- a/lib/Target/SubtargetFeature.cpp
+++ b/lib/Target/SubtargetFeature.cpp
@@ -199,6 +199,43 @@ void SubtargetFeatures::setCPUIfNone(const std::string &String) {
   if (Features[0].empty()) setCPU(String);
 }
 
+/// SetImpliedBits - For each feature that is (transitively) implied by this
+/// feature, set it.
+/// 
+static
+void SetImpliedBits(uint32_t &Bits, const SubtargetFeatureKV *FeatureEntry,
+                    const SubtargetFeatureKV *FeatureTable,
+                    size_t FeatureTableSize) {
+  for (size_t i = 0; i < FeatureTableSize; ++i) {
+    const SubtargetFeatureKV &FE = FeatureTable[i];
+
+    if (FeatureEntry->Value == FE.Value) continue;
+
+    if (FeatureEntry->Implies & FE.Value) {
+      Bits |= FE.Value;
+      SetImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
+    }
+  }
+}
+
+/// ClearImpliedBits - For each feature that (transitively) implies this
+/// feature, clear it.
+/// 
+static
+void ClearImpliedBits(uint32_t &Bits, const SubtargetFeatureKV *FeatureEntry,
+                      const SubtargetFeatureKV *FeatureTable,
+                      size_t FeatureTableSize) {
+  for (size_t i = 0; i < FeatureTableSize; ++i) {
+    const SubtargetFeatureKV &FE = FeatureTable[i];
+
+    if (FeatureEntry->Value == FE.Value) continue;
+
+    if (FE.Implies & FeatureEntry->Value) {
+      Bits &= ~FE.Value;
+      ClearImpliedBits(Bits, &FE, FeatureTable, FeatureTableSize);
+    }
+  }
+}
 
 /// getBits - Get feature bits.
 ///
@@ -251,8 +288,17 @@ uint32_t SubtargetFeatures::getBits(const SubtargetFeatureKV *CPUTable,
     // If there is a match
     if (FeatureEntry) {
       // Enable/disable feature in bits
-      if (isEnabled(Feature)) Bits |=  FeatureEntry->Value;
-      else                    Bits &= ~FeatureEntry->Value;
+      if (isEnabled(Feature)) {
+        Bits |=  FeatureEntry->Value;
+
+        // For each feature that this implies, set it.
+        SetImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
+      } else {
+        Bits &= ~FeatureEntry->Value;
+
+        // For each feature that implies this, clear it.
+        ClearImpliedBits(Bits, FeatureEntry, FeatureTable, FeatureTableSize);
+      }
     } else {
       cerr << "'" << Feature
            << "' is not a recognized feature for this target"
@@ -260,6 +306,7 @@ uint32_t SubtargetFeatures::getBits(const SubtargetFeatureKV *CPUTable,
            << "\n";
     }
   }
+
   return Bits;
 }
 
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