[LV] Assertion `Val && "isa<> used on a null pointer"' failed

[sjoerdmeijer]

Compile this:

int a;
extern bool b[];
char d, c;
void f() {
  for (int e(d); e; e += 4LL) {
    b[e] = 0;
    a += c;
  }
}

with:

clang++  -Ofast  -mcpu=grace  -c func.cpp

to trigger this assert:

llvm/include/llvm/Support/Casting.h:109: static bool llvm::isa_impl_cl<llvm::VPWidenCastRecipe, const llvm::VPRecipeBase *>::doit(const From *) [To = llvm::VPWidenCastRecipe, From = const llvm::VPRecipeBase *]: Assertion `Val && "isa<> used on a null pointer"' failed.

See also: https://godbolt.org/z/G9nM71bbr

[david-arm]

OK I'll take a look.

[david-arm]

I think I have a fix. We're attempting to match a partial reduction where the extended value lives outside the loop.

[david-arm]

@sjoerdmeijer FYI #148264