[PATCH] D133157: Add -sanitizer-coverage-control-flow

[Kostya Serebryany via Phabricator via llvm-commits]

kcc added inline comments.


================
Comment at: llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp:1062
+    for (auto SuccBB : successors(&BB)) {
+      if (SuccBB == &F.getEntryBlock())
+        CFs.push_back((Constant *)IRB.CreatePointerCast(&F, IntptrPtrTy));
----------------
Navidem wrote:
> kcc wrote:
> > hmmm... is it even possible?
> I was being cautious here for the branches (like `goto`) to the beginning of the function.
> But later once checked a concrete example, I was not able to produce such scenario.
> 
> something like the following code breaks the entry basic block:
> 
> ```
> int foo (int x) {
> top:
>   x += 5;
>   if (x > 5)
>     bar(x);
>   else
>     goto top;
> 
>   return x;
> }
> ```
> ```
> define dso_local i32 @foo(i32 noundef %x) #0 {
> entry:
>   %x.addr = alloca i32, align 4
>   store i32 %x, ptr %x.addr, align 4
>   br label %top
> 
> top:                                              ; preds = %if.else, %entry
>   %0 = load i32, ptr %x.addr, align 4
>   %add = add nsw i32 %0, 5
>   store i32 %add, ptr %x.addr, align 4
>   %1 = load i32, ptr %x.addr, align 4
>   %cmp = icmp sgt i32 %1, 5
>   br i1 %cmp, label %if.then, label %if.else
> 
> if.then:                                          ; preds = %top
>   %2 = load i32, ptr %x.addr, align 4
>   call void @bar(i32 noundef %2)
>   br label %if.end
> 
> if.else:                                          ; preds = %top
>   br label %top
> 
> if.end:                                           ; preds = %if.then
>   %3 = load i32, ptr %x.addr, align 4
>   ret i32 %3
> }
> ```
> 
> If you think it is impossible, I am fine with simplifying the code here.
yea, please simplify. ok to leave an assert


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  https://reviews.llvm.org/D133157/new/

https://reviews.llvm.org/D133157