[MC] Move the instruction latency computation from TargetSchedModel to MCSchedModel.

adibiagio · adibiagio · commit 30c1ba4834a9 · 2018-03-13T15:22:13.000Z
The goal is to make the latency information accessible through the MCSchedModel interface. This is particularly important for tools like llvm-mca that only have access to the MCSchedModel API. This partially fixes PR36676. No functional change intended. Differential Revision: https://reviews.llvm.org/D44383 llvm-svn: 327406
diff --git a/llvm/include/llvm/MC/MCSchedule.h b/llvm/include/llvm/MC/MCSchedule.h
@@ -21,6 +21,7 @@
 namespace llvm {
 
 struct InstrItinerary;
+class MCSubtargetInfo;
 
 /// Define a kind of processor resource that will be modeled by the scheduler.
 struct MCProcResourceDesc {
@@ -226,6 +227,10 @@ struct MCSchedModel {
     return &SchedClassTable[SchedClassIdx];
   }
 
+  /// Returns the latency value for the scheduling class.
+  static int computeInstrLatency(const MCSubtargetInfo &STI,
+                                 const MCSchedClassDesc &SCDesc);
+
   /// Returns the default initialized model.
   static const MCSchedModel &GetDefaultSchedModel() { return Default; }
   static const MCSchedModel Default;
diff --git a/llvm/lib/CodeGen/TargetSchedule.cpp b/llvm/lib/CodeGen/TargetSchedule.cpp
@@ -257,15 +257,7 @@ unsigned TargetSchedModel::computeOperandLatency(
 
 unsigned
 TargetSchedModel::computeInstrLatency(const MCSchedClassDesc &SCDesc) const {
-  unsigned Latency = 0;
-  for (unsigned DefIdx = 0, DefEnd = SCDesc.NumWriteLatencyEntries;
-       DefIdx != DefEnd; ++DefIdx) {
-    // Lookup the definition's write latency in SubtargetInfo.
-    const MCWriteLatencyEntry *WLEntry =
-      STI->getWriteLatencyEntry(&SCDesc, DefIdx);
-    Latency = std::max(Latency, capLatency(WLEntry->Cycles));
-  }
-  return Latency;
+  return capLatency(MCSchedModel::computeInstrLatency(*STI, SCDesc));
 }
 
 unsigned TargetSchedModel::computeInstrLatency(unsigned Opcode) const {
diff --git a/llvm/lib/MC/MCSchedule.cpp b/llvm/lib/MC/MCSchedule.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCSchedule.h"
+#include "llvm/MC/MCSubtargetInfo.h"
 #include <type_traits>
 
 using namespace llvm;
@@ -32,3 +33,19 @@ const MCSchedModel MCSchedModel::Default = {DefaultIssueWidth,
                                             0,
                                             0,
                                             nullptr};
+
+int MCSchedModel::computeInstrLatency(const MCSubtargetInfo &STI,
+                                      const MCSchedClassDesc &SCDesc) {
+  int Latency = 0;
+  for (unsigned DefIdx = 0, DefEnd = SCDesc.NumWriteLatencyEntries;
+       DefIdx != DefEnd; ++DefIdx) {
+    // Lookup the definition's write latency in SubtargetInfo.
+    const MCWriteLatencyEntry *WLEntry =
+        STI.getWriteLatencyEntry(&SCDesc, DefIdx);
+    // Early exit if we found an invalid latency.
+    if (WLEntry->Cycles < 0)
+      return WLEntry->Cycles;
+    Latency = std::max(Latency, static_cast<int>(WLEntry->Cycles));
+  }
+  return Latency;
+}
