[llvm] [CodeGen] Merge lowerConstantIntrinsics into pre-isel lowering (PR #97727)

[Björn Pettersson via llvm-commits]

================
@@ -285,6 +311,16 @@ bool PreISelIntrinsicLowering::lowerIntrinsics(Module &M) const {
     case Intrinsic::load_relative:
       Changed |= lowerLoadRelative(F);
       break;
+    case Intrinsic::is_constant:
+    case Intrinsic::objectsize:
+      Changed |= forEachCall(F, [&](CallInst *CI) {
+        Function *Parent = CI->getParent()->getParent();
+        TargetLibraryInfo &TLI = LookupTLI(*Parent);
+        bool Changed = lowerConstantIntrinsics(*Parent, TLI, /*DT=*/nullptr);
+        assert(Changed && "lowerConstantIntrinsics did not lower intrinsic");
----------------
bjope wrote:

This assert fails for input like this
```
define void @bbi_97828() {
  ret void

dead:
  %x = call i32 @llvm.objectsize.i32.p21(ptr addrspace(21) null, i1 false, i1 false, i1 false)
  br label %dead
}
```
since lowerConstantIntrinsics is doing an RPOT traversal to find out which intrinsics to lower. So it may fail to find CI, and then there is no changes.

https://github.com/llvm/llvm-project/pull/97727