Replace the statically generated hashtables for checking register relationships with just scanning the (typically tiny) static lists.

At the time I wrote this code (circa 2007), TargetRegisterInfo was using a std::set to perform these queries.  Switching to the static hashtables was an obvious improvement, but in reality there's no reason to do anything other than scan.
With this change, total LLC time on a whole-program 403.gcc is reduced by approximately 1.5%, almost all of which comes from a 15% reduction in LiveVariables time.  It also reduces the binary size of LLC by 86KB, thanks to eliminating a bunch of very large static tables.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133051 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 40 deletions

diff --git a/include/llvm/Target/TargetRegisterInfo.h b/include/llvm/Target/TargetRegisterInfo.h
index f85cdeb049..dc2d07aa4d 100644
--- a/include/llvm/Target/TargetRegisterInfo.h
+++ b/include/llvm/Target/TargetRegisterInfo.h
@@ -285,11 +285,6 @@ public:
 /// descriptor.
 ///
 class TargetRegisterInfo {
-protected:
-  const unsigned* SubregHash;
-  const unsigned SubregHashSize;
-  const unsigned* AliasesHash;
-  const unsigned AliasesHashSize;
 public:
   typedef const TargetRegisterClass * const * regclass_iterator;
 private:
@@ -307,11 +302,7 @@ protected:
                      regclass_iterator RegClassEnd,
                      const char *const *subregindexnames,
                      int CallFrameSetupOpcode = -1,
-                     int CallFrameDestroyOpcode = -1,
-                     const unsigned* subregs = 0,
-                     const unsigned subregsize = 0,
-                     const unsigned* aliases = 0,
-                     const unsigned aliasessize = 0);
+                     int CallFrameDestroyOpcode = -1);
   virtual ~TargetRegisterInfo();
 public:
 
@@ -468,50 +459,28 @@ public:
   /// regsOverlap - Returns true if the two registers are equal or alias each
   /// other. The registers may be virtual register.
   bool regsOverlap(unsigned regA, unsigned regB) const {
-    if (regA == regB)
-      return true;
-
-    if (regA > regB)
-      std::swap(regA, regB);
-
+    if (regA == regB) return true;
     if (isVirtualRegister(regA) || isVirtualRegister(regB))
       return false;
-
-    // regA and regB are distinct physical registers. Do they alias?
-    size_t index = (regA * 11 + regB * 97) & (AliasesHashSize-1);
-    unsigned ProbeAmt = 1;
-    while (AliasesHash[index*2] != 0 && AliasesHash[index*2+1] != 0) {
-      if (AliasesHash[index*2] == regA && AliasesHash[index*2+1] == regB)
-        return true;
-
-      index = (index + ProbeAmt) & (AliasesHashSize-1);
-      ProbeAmt += 1;
+    for (const unsigned *regList = getOverlaps(regA)+1; *regList; ++regList) {
+      if (*regList == regB) return true;
     }
-
     return false;
   }
 
   /// isSubRegister - Returns true if regB is a sub-register of regA.
   ///
   bool isSubRegister(unsigned regA, unsigned regB) const {
-    // SubregHash is a simple quadratically probed hash table.
-    size_t index = (regA * 11 + regB * 97) & (SubregHashSize-1);
-    unsigned ProbeAmt = 1;
-    while (SubregHash[index*2] != 0 && SubregHash[index*2+1] != 0) {
-      if (SubregHash[index*2] == regA && SubregHash[index*2+1] == regB)
-        return true;
-
-      index = (index + ProbeAmt) & (SubregHashSize-1);
-      ProbeAmt += 1;
-    }
-
-    return false;
+    return isSuperRegister(regB, regA);
   }
 
   /// isSuperRegister - Returns true if regB is a super-register of regA.
   ///
   bool isSuperRegister(unsigned regA, unsigned regB) const {
-    return isSubRegister(regB, regA);
+    for (const unsigned *regList = getSuperRegisters(regA); *regList;++regList){
+      if (*regList == regB) return true;
+    }
+    return false;
   }
 
   /// getCalleeSavedRegs - Return a null-terminated list of all of the