2 files changed, 22 insertions, 4 deletions
diff --git a/llvm/lib/Target/README.txt b/llvm/lib/Target/README.txt
index d13ea736a10..5cc4fe027a8 100644
--- a/llvm/lib/Target/README.txt
+++ b/llvm/lib/Target/README.txt
@@ -2009,6 +2009,28 @@ entry:
 
 //===---------------------------------------------------------------------===//
 
+This code can be seen in viterbi:
+
+  %64 = call noalias i8* @malloc(i64 %62) nounwind
+...
+  %67 = call i64 @llvm.objectsize.i64(i8* %64, i1 false) nounwind
+  %68 = call i8* @__memset_chk(i8* %64, i32 0, i64 %62, i64 %67) nounwind
+
+llvm.objectsize.i64 should be taught about malloc/calloc, allowing it to
+fold to %62.  This is a security win (overflows of malloc will get caught)
+and also a performance win by exposing more memsets to the optimizer.
+
+This occurs several times in viterbi.
+
+Note that this would change the semantics of @llvm.objectsize which by its
+current definition always folds to a constant. We also should make sure that
+we remove checking in code like
+
+  char *p = malloc(strlen(s)+1);
+  __strcpy_chk(p, s, __builtin_objectsize(p, 0));
+
+//===---------------------------------------------------------------------===//
+
 This code (from Benchmarks/Dhrystone/dry.c):
 
 define i32 @Func1(i32, i32) nounwind readnone optsize ssp {
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index ecd2243c35d..bd451ebcac9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -304,10 +304,6 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
         if (Value *NElems = getMallocArraySize(MI, TD, true))
           if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
             Size = NElements->getZExtValue() * TD->getTypeAllocSize(MallocType);
-
-      // If there is no offset we can just return the size passed to malloc.
-      if (Offset == 0)
-        return ReplaceInstUsesWith(CI, MI->getArgOperand(0));
     }
 
     // Do not return "I don't know" here. Later optimization passes could