implement a FIXME: limit the depth that DecomposeGEPExpression goes the same

way that getUnderlyingObject does it. 

This fixes the 'DecomposeGEPExpression and getUnderlyingObject disagree!' 
assertion on sqlite3.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90038 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 26 insertions, 4 deletions

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 3e6af58..31d3ccc 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -1028,9 +1028,11 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
 const Value *llvm::DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
                  SmallVectorImpl<std::pair<const Value*, int64_t> > &VarIndices,
                                           const TargetData *TD) {
-  // FIXME: Should limit depth like getUnderlyingObject?
+  // Limit recursion depth to limit compile time in crazy cases.
+  unsigned MaxLookup = 6;
+  
   BaseOffs = 0;
-  while (1) {
+  do {
     // See if this is a bitcast or GEP.
     const Operator *Op = dyn_cast<Operator>(V);
     if (Op == 0) {
@@ -1128,7 +1130,10 @@ const Value *llvm::DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
     
     // Analyze the base pointer next.
     V = GEPOp->getOperand(0);
-  }
+  } while (--MaxLookup);
+  
+  // If the chain of expressions is too deep, just return early.
+  return V;
 }
 
 
diff --git a/test/Transforms/DeadStoreElimination/crash.ll b/test/Transforms/DeadStoreElimination/crash.ll
index 7f82cbf..f89f8f5 100644
--- a/test/Transforms/DeadStoreElimination/crash.ll
+++ b/test/Transforms/DeadStoreElimination/crash.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -dse | llvm-dis
+; RUN: opt < %s -dse -S
 
 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-f80:128:128"
 target triple = "i386-apple-darwin10.0"
@@ -24,3 +24,20 @@ bb:                                               ; preds = %bb, %entry
   %2 = tail call signext i8 @foo(i8 signext undef, i8 signext 1) nounwind ; <i8> [#uses=1]
   br label %bb
 }
+
+define fastcc i32 @test2() nounwind ssp {
+bb14:                                             ; preds = %bb4
+  %0 = bitcast i8* undef to i8**                  ; <i8**> [#uses=1]
+  %1 = getelementptr inbounds i8** %0, i64 undef  ; <i8**> [#uses=1]
+  %2 = bitcast i8** %1 to i16*                    ; <i16*> [#uses=2]
+  %3 = getelementptr inbounds i16* %2, i64 undef  ; <i16*> [#uses=1]
+  %4 = bitcast i16* %3 to i8*                     ; <i8*> [#uses=1]
+  %5 = getelementptr inbounds i8* %4, i64 undef   ; <i8*> [#uses=1]
+  %6 = getelementptr inbounds i16* %2, i64 undef  ; <i16*> [#uses=1]
+  store i16 undef, i16* %6, align 2
+  %7 = getelementptr inbounds i8* %5, i64 undef   ; <i8*> [#uses=1]
+  call void @llvm.memcpy.i64(i8* %7, i8* undef, i64 undef, i32 1) nounwind
+  unreachable
+}
+
+declare void @llvm.memcpy.i64(i8* nocapture, i8* nocapture, i64, i32) nounwind