[llvm-commits] [llvm] r51875 - in /llvm/trunk: lib/Analysis/BasicAliasAnalysis.cpp test/Analysis/BasicAA/2008-06-02-GEPTailCrash.ll

Wojciech Matyjewicz wmatyjewicz at fastmail.fm
Mon Jun 2 10:26:12 PDT 2008


Author: wmat
Date: Mon Jun  2 12:26:12 2008
New Revision: 51875

URL: http://llvm.org/viewvc/llvm-project?rev=51875&view=rev
Log:
Fixes PR2395. Looking for a constant in a GEP tail (when the first GEP 
is longer than the second one) should stop after finding one. Added break 
instruction guarantees it. It also changes difference between offsets to 
absolute value of this difference in the condition.

Added:
    llvm/trunk/test/Analysis/BasicAA/2008-06-02-GEPTailCrash.ll
Modified:
    llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=51875&r1=51874&r2=51875&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Mon Jun  2 12:26:12 2008
@@ -687,7 +687,7 @@
         if (isa<ConstantInt>(GEP1Ops[i]) && 
             !cast<ConstantInt>(GEP1Ops[i])->isZero()) {
           // Yup, there's a constant in the tail.  Set all variables to
-          // constants in the GEP instruction to make it suiteable for
+          // constants in the GEP instruction to make it suitable for
           // TargetData::getIndexedOffset.
           for (i = 0; i != MaxOperands; ++i)
             if (!isa<ConstantInt>(GEP1Ops[i]))
@@ -702,9 +702,15 @@
           int64_t Offset2 = TD.getIndexedOffset(GEPPointerTy, GEP1Ops,
                                                 MinOperands);
 
+          // Make sure we compare the absolute difference.
+          if (Offset1 > Offset2)
+            std::swap(Offset1, Offset2);
+
           // If the tail provided a bit enough offset, return noalias!
           if ((uint64_t)(Offset2-Offset1) >= SizeMax)
             return NoAlias;
+          // Otherwise break - we don't look for another constant in the tail.
+          break;
         }
     }
 

Added: llvm/trunk/test/Analysis/BasicAA/2008-06-02-GEPTailCrash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/2008-06-02-GEPTailCrash.ll?rev=51875&view=auto

==============================================================================
--- llvm/trunk/test/Analysis/BasicAA/2008-06-02-GEPTailCrash.ll (added)
+++ llvm/trunk/test/Analysis/BasicAA/2008-06-02-GEPTailCrash.ll Mon Jun  2 12:26:12 2008
@@ -0,0 +1,15 @@
+; RUN: llvm-as < %s | opt -gvn -disable-output
+; PR2395
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
+target triple = "i686-pc-linux-gnu"
+	%struct.S291 = type <{ %union.anon, i32 }>
+	%union.anon = type {  }
+ at a291 = external global [5 x %struct.S291]		; <[5 x %struct.S291]*> [#uses=2]
+
+define void @test291() nounwind  {
+entry:
+	store i32 1138410269, i32* getelementptr ([5 x %struct.S291]* @a291, i32 0, i32 2, i32 1)
+	%tmp54 = load i32* bitcast (%struct.S291* getelementptr ([5 x %struct.S291]* @a291, i32 0, i32 2) to i32*), align 4		; <i32> [#uses=0]
+	unreachable
+}





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