commit 07e8c36dc73fa56357f0da4ac71c559fe952b31d
author Michael Kruse <llvm@meinersbur.de> Mon Jul 24 12:43:27 2017 +0000
committer Michael Kruse <llvm@meinersbur.de> Mon Jul 24 12:43:27 2017 +0000
tree d6b599dea44fe7d77f43324496bc288365fc817f
parent e2699b572e99110dc647a9f9dd1147b70db40412

[ForwardOpTree] Support read-only value uses.

Read-only values (values defined before the SCoP) require special
handing with -polly-analyze-read-only-scalars=true (which is the
default). If active, each use of a value requires a read access.
When a copied value uses a read-only value, we must also ensure that
such a MemoryAccess is available or is created.

Differential Revision: https://reviews.llvm.org/D35764

llvm-svn: 308876

polly/lib/Transform/ForwardOpTree.cpp

diff --git a/polly/lib/Transform/ForwardOpTree.cpp b/polly/lib/Transform/ForwardOpTree.cpp
index e0fd578..fe5a631 100644
--- a/polly/lib/Transform/ForwardOpTree.cpp
+++ b/polly/lib/Transform/ForwardOpTree.cpp
@@ -13,6 +13,7 @@
 
 #include "polly/ForwardOpTree.h"
 
+#include "polly/ScopBuilder.h"
 #include "polly/ScopInfo.h"
 #include "polly/ScopPass.h"
 #include "polly/Support/GICHelper.h"
@@ -25,6 +26,7 @@
 using namespace llvm;
 
 STATISTIC(TotalInstructionsCopied, "Number of copied instructions");
+STATISTIC(TotalReadOnlyCopied, "Number of copied read-only accesses");
 STATISTIC(TotalForwardedTrees, "Number of forwarded operand trees");
 STATISTIC(TotalModifiedStmts,
           "Number of statements with at least one forwarded tree");
@@ -37,6 +39,7 @@
 enum ForwardingDecision {
   FD_CannotForward,
   FD_CanForward,
+  FD_CanForwardTree,
   FD_DidForward,
 };
 
@@ -58,6 +61,9 @@
   /// How many instructions have been copied to other statements.
   int NumInstructionsCopied = 0;
 
+  /// How many read-only accesses have been copied.
+  int NumReadOnlyCopied = 0;
+
   /// How many operand trees have been forwarded.
   int NumForwardedTrees = 0;
 
@@ -71,6 +77,8 @@
     OS.indent(Indent) << "Statistics {\n";
     OS.indent(Indent + 4) << "Instructions copied: " << NumInstructionsCopied
                           << '\n';
+    OS.indent(Indent + 4) << "Read-only accesses copied: " << NumReadOnlyCopied
+                          << '\n';
     OS.indent(Indent + 4) << "Operand trees forwarded: " << NumForwardedTrees
                           << '\n';
     OS.indent(Indent + 4) << "Statements with forwarded operand trees: "
@@ -132,9 +140,16 @@
       return FD_CannotForward;
 
     case VirtualUse::ReadOnly:
-      // Not supported yet.
-      DEBUG(dbgs() << "    Cannot forward read-only val: " << *UseVal << "\n");
-      return FD_CannotForward;
+      if (!DoIt)
+        return FD_CanForward;
+
+      // If we model read-only scalars, we need to create a MemoryAccess for it.
+      if (ModelReadOnlyScalars)
+        TargetStmt->ensureValueRead(UseVal);
+
+      NumReadOnlyCopied++;
+      TotalReadOnlyCopied++;
+      return FD_DidForward;
 
     case VirtualUse::Intra:
     case VirtualUse::Inter:
@@ -183,6 +198,7 @@
           return FD_CannotForward;
 
         case FD_CanForward:
+        case FD_CanForwardTree:
           assert(!DoIt);
           break;
 
@@ -194,7 +210,7 @@
 
       if (DoIt)
         return FD_DidForward;
-      return FD_CanForward;
+      return FD_CanForwardTree;
     }
 
     llvm_unreachable("Case unhandled");
@@ -211,7 +227,7 @@
     ForwardingDecision Assessment =
         canForwardTree(Stmt, RA->getAccessValue(), Stmt, InLoop, false);
     assert(Assessment != FD_DidForward);
-    if (Assessment == FD_CannotForward)
+    if (Assessment != FD_CanForwardTree)
       return false;
 
     ForwardingDecision Execution =