[llvm-commits] [llvm] r157977 - in /llvm/trunk: include/llvm/CodeGen/ScheduleHazardRecognizer.h lib/CodeGen/ScoreboardHazardRecognizer.cpp

[Andrew Trick]

Author: atrick
Date: Mon Jun  4 22:44:32 2012
New Revision: 157977

URL: http://llvm.org/viewvc/llvm-project?rev=157977&view=rev
Log:
misched: Allow disabling scoreboard hazard checking for subtargets with a
valid itinerary but no pipeline stages.

An itinerary can contain useful scheduling information without specifying pipeline stages for each instruction.

Modified:
    llvm/trunk/include/llvm/CodeGen/ScheduleHazardRecognizer.h
    llvm/trunk/lib/CodeGen/ScoreboardHazardRecognizer.cpp

Modified: llvm/trunk/include/llvm/CodeGen/ScheduleHazardRecognizer.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/ScheduleHazardRecognizer.h?rev=157977&r1=157976&r2=157977&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/ScheduleHazardRecognizer.h (original)
+++ llvm/trunk/include/llvm/CodeGen/ScheduleHazardRecognizer.h Mon Jun  4 22:44:32 2012
@@ -46,6 +46,8 @@
 
   /// atIssueLimit - Return true if no more instructions may be issued in this
   /// cycle.
+  ///
+  /// FIXME: remove this once MachineScheduler is the only client.
   virtual bool atIssueLimit() const { return false; }
 
   /// getHazardType - Return the hazard type of emitting this node.  There are

Modified: llvm/trunk/lib/CodeGen/ScoreboardHazardRecognizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/ScoreboardHazardRecognizer.cpp?rev=157977&r1=157976&r2=157977&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/ScoreboardHazardRecognizer.cpp (original)
+++ llvm/trunk/lib/CodeGen/ScoreboardHazardRecognizer.cpp Mon Jun  4 22:44:32 2012
@@ -39,9 +39,9 @@
   DebugType = ParentDebugType;
 #endif
 
-  // Determine the maximum depth of any itinerary. This determines the
-  // depth of the scoreboard. We always make the scoreboard at least 1
-  // cycle deep to avoid dealing with the boundary condition.
+  // Determine the maximum depth of any itinerary. This determines the depth of
+  // the scoreboard. We always make the scoreboard at least 1 cycle deep to
+  // avoid dealing with the boundary condition.
   unsigned ScoreboardDepth = 1;
   if (ItinData && !ItinData->isEmpty()) {
     IssueWidth = ItinData->IssueWidth;
@@ -63,16 +63,22 @@
       // Find the next power-of-2 >= ItinDepth
       while (ItinDepth > ScoreboardDepth) {
         ScoreboardDepth *= 2;
+        // Don't set MaxLookAhead until we find at least one nonzero stage.
+        // This way, an itinerary with no stages has MaxLookAhead==0, which
+        // completely bypasses the scoreboard hazard logic.
+        MaxLookAhead = ScoreboardDepth;
       }
     }
-    MaxLookAhead = ScoreboardDepth;
   }
 
   ReservedScoreboard.reset(ScoreboardDepth);
   RequiredScoreboard.reset(ScoreboardDepth);
 
-  DEBUG(dbgs() << "Using scoreboard hazard recognizer: Depth = "
-               << ScoreboardDepth << '\n');
+  if (!MaxLookAhead)
+    DEBUG(dbgs() << "Disabled scoreboard hazard recognizer\n");
+  else
+    DEBUG(dbgs() << "Using scoreboard hazard recognizer: Depth = "
+          << ScoreboardDepth << '\n');
 }
 
 void ScoreboardHazardRecognizer::Reset() {