[TargetTransformInfo] Check if function pointer is valid before calling isLoweredToCall

[Carrot]

Summary

Function isLoweredToCall can only accept non-null function pointer, but a function pointer can be null for indirect function call. So check it before calling isLoweredToCall from getInstructionLatency.

[mcrosier]

Would it make sense to also add an assertion in isLoweredToCall asserting that F is non-null?

Also, is this something that can be tested? Something that shows the compiler doesn't segfault would be sufficient.

[mcrosier]

Also, please be sure to include full context with your patches. This is generally done with -U git option (e.g., git show HEAD -U999999 > mypatch.patch).

[Carrot]

In D38204#880129, @mcrosier wrote:

Would it make sense to also add an assertion in isLoweredToCall asserting that F is non-null?

Also, is this something that can be tested? Something that shows the compiler doesn't segfault would be sufficient.

done.

[Carrot]

ping

[echristo]

LGTM. Thanks!

include/llvm/Analysis/TargetTransformInfoImpl.h

public:
 
   bool isAlwaysUniform(const Value *V) { return false; }
 
   unsigned getFlatAddressSpace () {
     return -1;
   }
 
   bool isLoweredToCall(const Function *F) {
+    assert(F && "A concrete function must be provided to this routine.");
+
     // FIXME: These should almost certainly not be handled here, and instead
     // handled with the help of TLI or the target itself. This was largely
     // ported from existing analysis heuristics here so that such refactorings
     // can take place in the future.
 
     if (F->isIntrinsic())
       return false;
 
if (isa<LoadInst>(I))
       return 4;
 
     Type *DstTy = I->getType();
 
     // Usually an intrinsic is a simple instruction.
     // A real function call is much slower.
     if (auto *CI = dyn_cast<CallInst>(I)) {
       const Function *F = CI->getCalledFunction();
-      if (static_cast<T *>(this)->isLoweredToCall(F))
+      if (!F || static_cast<T *>(this)->isLoweredToCall(F))
         return 40;
       // Some intrinsics return a value and a flag, we use the value type
       // to decide its latency.
       if (StructType* StructTy = dyn_cast<StructType>(DstTy))
         DstTy = StructTy->getElementType(0);
       // Fall through to simple instructions.
     }
 

test/Analysis/CostModel/X86/costmodel.ll

define i64 @foo(i64 %arg) {
   ; LATENCY:  cost of 0 {{.*}} trunc
   ; CODESIZE: cost of 0 {{.*}} trunc
   %TC = trunc i64 undef to i32
 
   ; LATENCY:  cost of 1 {{.*}} call
   ; CODESIZE: cost of 1 {{.*}} call
   %uadd = call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 undef, i32 undef)
 
+  ; LATENCY:  cost of 40 {{.*}} call void undef
+  ; CODESIZE: cost of 1 {{.*}} call void undef
+  call void undef()
+
   ; LATENCY:  cost of 1 {{.*}} ret
   ; CODESIZE: cost of 1 {{.*}} ret
   ret i64 undef
 }