[llvm-commits] [llvm] r153789 - /llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Fri Mar 30 19:06:44 2012
New Revision: 153789

URL: http://llvm.org/viewvc/llvm-project?rev=153789&view=rev
Log:
Add a 2 byte safety margin in offset computations.

ARMConstantIslandPass still has bugs where jump table compression can
cause constant pool entries to go out of range.

Add a safety margin of 2 bytes when placing constant islands, but use
the real max displacement for verification.

<rdar://problem/11156595>

Modified:
    llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp

Modified: llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp?rev=153789&r1=153788&r2=153789&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMConstantIslandPass.cpp Fri Mar 30 19:06:44 2012
@@ -209,8 +209,9 @@
       }
       /// getMaxDisp - Returns the maximum displacement supported by MI.
       /// Correct for unknown alignment.
+      /// Conservatively subtract 2 bytes to handle weird alignment effects.
       unsigned getMaxDisp() const {
-        return KnownAlignment ? MaxDisp : MaxDisp - 2;
+        return (KnownAlignment ? MaxDisp : MaxDisp - 2) - 2;
       }
     };
 
@@ -350,7 +351,9 @@
   for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) {
     CPUser &U = CPUsers[i];
     unsigned UserOffset = getUserOffset(U);
-    if (isCPEntryInRange(U.MI, UserOffset, U.CPEMI, U.getMaxDisp(), U.NegOk,
+    // Verify offset using the real max displacement without the safety
+    // adjustment.
+    if (isCPEntryInRange(U.MI, UserOffset, U.CPEMI, U.getMaxDisp()+2, U.NegOk,
                          /* DoDump = */ true)) {
       DEBUG(dbgs() << "OK\n");
       continue;