//===---------------------------------------------------------------------===//
+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 {
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
ret i32 %objsize
}
-define i32 @test8(i32 %x) {
-; CHECK: @test8
- %alloc = call noalias i8* @malloc(i32 %x) nounwind
- %objsize = call i32 @llvm.objectsize.i32(i8* %alloc, i1 false) nounwind readonly
-; CHECK-NEXT: ret i32 %x
- ret i32 %objsize
-}
-
-define i32 @test9(i32 %x) {
-; CHECK: @test9
- %alloc = call noalias i8* @malloc(i32 %x) nounwind
- %gep = getelementptr inbounds i8* %alloc, i32 16
- %objsize = call i32 @llvm.objectsize.i32(i8* %gep, i1 false) nounwind readonly
-; CHECK-NOT: ret i32 %x
- ret i32 %objsize
-}
-
-define i8* @test10(i32 %x) {
-; CHECK: @test10
- %alloc = call noalias i8* @malloc(i32 %x) nounwind
- %objsize = call i32 @llvm.objectsize.i32(i8* %alloc, i1 false) nounwind readonly
- tail call i8* @__memset_chk(i8* %alloc, i32 0, i32 %x, i32 %objsize) nounwind
-; CHECK-NOT: @llvm.objectsize
-; CHECK: @llvm.memset
- ret i8* %alloc
-; CHECK: ret i8*
-}