[llvm-commits] [llvm] r116210 - /llvm/trunk/lib/CodeGen/VirtRegRewriter.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Mon Oct 11 13:10:36 2010
New Revision: 116210

URL: http://llvm.org/viewvc/llvm-project?rev=116210&view=rev
Log:
Properly handle reloading and spilling around partial redefines in
LocalRewriter.

This is a bit of a hack that adds an implicit use operand to model the
read-modify-write nature of a partial redef. Uses and defs are rewritten in
separate passes, and a single operand would never be processed twice.

<rdar://problem/8518892>

Modified:
    llvm/trunk/lib/CodeGen/VirtRegRewriter.cpp

Modified: llvm/trunk/lib/CodeGen/VirtRegRewriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/VirtRegRewriter.cpp?rev=116210&r1=116209&r2=116210&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/VirtRegRewriter.cpp (original)
+++ llvm/trunk/lib/CodeGen/VirtRegRewriter.cpp Mon Oct 11 13:10:36 2010
@@ -1894,6 +1894,20 @@
       VirtUseOps.insert(VirtUseOps.begin(), i);
     else
       VirtUseOps.push_back(i);
+
+    // A partial def causes problems because the same operand both reads and
+    // writes the register. This rewriter is designed to rewrite uses and defs
+    // separately, so a partial def would already have been rewritten to a
+    // physreg by the time we get to processing defs.
+    // Add an implicit use operand to model the partial def.
+    if (MO.isDef() && MO.getSubReg() && MI.readsVirtualRegister(VirtReg) &&
+        MI.findRegisterUseOperandIdx(VirtReg) == -1) {
+      VirtUseOps.insert(VirtUseOps.begin(), MI.getNumOperands());
+      MI.addOperand(MachineOperand::CreateReg(VirtReg,
+                                              false,  // isDef
+                                              true)); // isImplicit
+      DEBUG(dbgs() << "Partial redef: " << MI);
+    }
   }
 
   // Process all of the spilled uses and all non spilled reg references.