commit f81a8d03c109558b9d322c8864660532455ac3cf
author Krzysztof Parzyszek <kparzysz@codeaurora.org> Fri Mar 16 20:55:49 2018 +0000
committer Krzysztof Parzyszek <kparzysz@codeaurora.org> Fri Mar 16 20:55:49 2018 +0000
tree 3e7c09ef4ff11933245f8a838019bc60336e3348
parent 332a3e075fbfae36445abe3bd2140507184170cc

[Hexagon] Avoid bank conflicts in post-RA scheduler

Avoid scheduling two loads in such a way that they would end up in the
same packet. If there is a load in a packet, try to schedule a non-load
next.

Patch by Brendon Cahoon.

llvm-svn: 327742

llvm/lib/Target/Hexagon/HexagonHazardRecognizer.cpp

diff --git a/llvm/lib/Target/Hexagon/HexagonHazardRecognizer.cpp b/llvm/lib/Target/Hexagon/HexagonHazardRecognizer.cpp
index 036b186..cae7318 100644
--- a/llvm/lib/Target/Hexagon/HexagonHazardRecognizer.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonHazardRecognizer.cpp
@@ -31,6 +31,7 @@
   PacketNum = 0;
   UsesDotCur = nullptr;
   DotCurPNum = -1;
+  UsesLoad = false;
   RegDefs.clear();
 }
 
@@ -78,15 +79,20 @@
     UsesDotCur = nullptr;
     DotCurPNum = -1;
   }
+  UsesLoad = false;
   PacketNum++;
   RegDefs.clear();
 }
 
-/// If a packet contains a dot cur instruction, then we may prefer the
-/// instruction that can use the dot cur result. Or, if the use
-/// isn't scheduled in the same packet, then prefer other instructions
-/// in the subsequent packet.
+/// Handle the cases when we prefer one instruction over another. Case 1 - we
+/// prefer not to generate multiple loads in the packet to avoid a potential
+/// bank conflict. Case 2 - if a packet contains a dot cur instruction, then we
+/// prefer the instruction that can use the dot cur result. However, if the use
+/// is not scheduled in the same packet, then prefer other instructions in the
+/// subsequent packet.
 bool HexagonHazardRecognizer::ShouldPreferAnother(SUnit *SU) {
+  if (UsesLoad && SU->isInstr() && SU->getInstr()->mayLoad())
+    return true;
   return UsesDotCur && ((SU == UsesDotCur) ^ (DotCurPNum == (int)PacketNum));
 }
 
@@ -137,4 +143,6 @@
     UsesDotCur = nullptr;
     DotCurPNum = -1;
   }
+
+  UsesLoad = MI->mayLoad();
 }