[llvm-commits] [llvm] r90038 - in /llvm/trunk: lib/Analysis/ValueTracking.cpp test/Transforms/DeadStoreElimination/crash.ll

[Chris Lattner]

Author: lattner
Date: Sat Nov 28 09:12:41 2009
New Revision: 90038

URL: http://llvm.org/viewvc/llvm-project?rev=90038&view=rev
Log:
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.


Modified:
    llvm/trunk/lib/Analysis/ValueTracking.cpp
    llvm/trunk/test/Transforms/DeadStoreElimination/crash.ll

Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=90038&r1=90037&r2=90038&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Sat Nov 28 09:12:41 2009
@@ -1028,9 +1028,11 @@
 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 @@
     
     // Analyze the base pointer next.
     V = GEPOp->getOperand(0);
-  }
+  } while (--MaxLookup);
+  
+  // If the chain of expressions is too deep, just return early.
+  return V;
 }
 
 

Modified: llvm/trunk/test/Transforms/DeadStoreElimination/crash.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadStoreElimination/crash.ll?rev=90038&r1=90037&r2=90038&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/DeadStoreElimination/crash.ll (original)
+++ llvm/trunk/test/Transforms/DeadStoreElimination/crash.ll Sat Nov 28 09:12:41 2009
@@ -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 @@
   %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