LLVM 24: vec-reserve-extend test failing

Sample failure:

/workspace/tests/codegen-llvm/vec-reserve-extend.rs:10:16: error: CHECK-NOT: excluded string found in input
 // CHECK-NOT: call {{.*}}reserve
               ^
/workspace/build/x86_64-unknown-linux-gnu/test/codegen-llvm/vec-reserve-extend/vec-reserve-extend.ll:306:3: note: found here
; call <alloc::raw_vec::RawVecInner<_>>::reserve::do_reserve_and_handle::<alloc::alloc::Global>

based on some digging, I think this is from llvm/llvm-project@7a3aa7da4c02 - truthfully I'm not sure if it's a bug in the optimizer change or if we need to sprinkle some more hints for LLVM into the code on our side. New IR output:

; Function Attrs: nonlazybind uwtable
define void @should_reserve_once(ptr noalias nofree noundef align 8 captures(none) dereferenceable(24) %v) unnamed_addr #2 personality ptr @rust_eh_personality !guid !45 {
start:
  %self3.i.i = alloca [24 x i8], align 8
  %e.i = alloca [16 x i8], align 8
  %0 = getelementptr inbounds nuw i8, ptr %v, i64 16
  %_6 = load i64, ptr %0, align 8, !noundef !28
  tail call void @llvm.experimental.noalias.scope.decl(metadata !46)
  %self4.i = load i64, ptr %v, align 8, !range !27, !alias.scope !46, !noundef !28
  %_11.i = sub i64 %self4.i, %_6
  %_5.i = icmp ult i64 %_11.i, 3
  br i1 %_5.i, label %bb1.i, label %_RINvMsk_NtCsbrQcgdVahqB_5alloc3vecINtB6_3VechE14extend_trustedINtNtNtCs9cuWXJ791ES_4core5array4iter8IntoIterhKj3_EECseHTl9kyFgP7_18vec_reserve_extend.exit

bb1.i:                                            ; preds = %start
  tail call void @llvm.experimental.noalias.scope.decl(metadata !49)
  %_25.1.i.i = icmp ugt i64 %_6, -4
  br i1 %_25.1.i.i, label %bb2.i, label %bb9.i.i

bb9.i.i:                                          ; preds = %bb1.i
  %_25.0.i.i = add nuw i64 %_6, 3
  %v16.i.i = shl nuw i64 %self4.i, 1
  %..i.i.i = tail call noundef i64 @llvm.umax.i64(i64 %_25.0.i.i, i64 range(i64 0, -1) %v16.i.i)
  %..i16.i.i = tail call noundef i64 @llvm.umax.i64(i64 %..i.i.i, i64 8)
  call void @llvm.lifetime.start.p0(ptr nonnull %self3.i.i), !noalias !52
  %1 = getelementptr inbounds nuw i8, ptr %v, i64 8
  %self.val15.i.i = load ptr, ptr %1, align 8, !alias.scope !52
; call <alloc::raw_vec::RawVecInner>::finish_grow
  call fastcc void @_RNvMs5_NtCsbrQcgdVahqB_5alloc7raw_vecNtB5_11RawVecInner11finish_growCseHTl9kyFgP7_18vec_reserve_extend(ptr noalias nofree noundef align 8 captures(none) dereferenceable(24) %self3.i.i, i64 %self4.i, ptr %self.val15.i.i, i64 noundef %..i16.i.i)
  %_37.i.i = load i64, ptr %self3.i.i, align 8, !range !29, !noalias !52, !noundef !28
  %2 = trunc nuw i64 %_37.i.i to i1
  %3 = getelementptr inbounds nuw i8, ptr %self3.i.i, i64 8
  br i1 %2, label %bb18.i.i, label %_RNvMNtCs9cuWXJ791ES_4core6resultINtB2_6ResultuNtNtCsbrQcgdVahqB_5alloc11collections15TryReserveErrorE6unwrapCseHTl9kyFgP7_18vec_reserve_extend.exit

bb18.i.i:                                         ; preds = %bb9.i.i
  %e.0.i.i = load i64, ptr %3, align 8, !range !30, !noalias !52, !noundef !28
  %4 = getelementptr inbounds nuw i8, ptr %self3.i.i, i64 16
  %e.1.i.i = load i64, ptr %4, align 8, !noalias !52
  call void @llvm.lifetime.end.p0(ptr nonnull %self3.i.i), !noalias !52
  br label %bb2.i

bb2.i:                                            ; preds = %bb1.i, %bb18.i.i
  %_0.sroa.3.0.i.ph = phi i64 [ %e.1.i.i, %bb18.i.i ], [ undef, %bb1.i ]
  %_0.sroa.0.0.i.ph = phi i64 [ %e.0.i.i, %bb18.i.i ], [ 0, %bb1.i ]
  call void @llvm.lifetime.start.p0(ptr nonnull %e.i)
  store i64 %_0.sroa.0.0.i.ph, ptr %e.i, align 8
  %5 = getelementptr inbounds nuw i8, ptr %e.i, i64 8
  store i64 %_0.sroa.3.0.i.ph, ptr %5, align 8
; call core::result::unwrap_failed
  call void @_RNvNtCs9cuWXJ791ES_4core6result13unwrap_failed(ptr noalias nofree noundef nonnull readonly captures(address, read_provenance) @alloc_00ae4b301f7fab8ac9617c03fcbd7274, i64 noundef 43, ptr noundef nonnull %e.i, ptr noalias nofree noundef readonly align 8 captures(address, read_provenance) dereferenceable(32) @vtable.0, ptr noalias nofree noundef readonly align 8 captures(address, read_provenance) dereferenceable(24) @alloc_11754d6f2273df2df0dcb4d09d8ddd63) #15
  unreachable

_RNvMNtCs9cuWXJ791ES_4core6resultINtB2_6ResultuNtNtCsbrQcgdVahqB_5alloc11collections15TryReserveErrorE6unwrapCseHTl9kyFgP7_18vec_reserve_extend.exit: ; preds = %bb9.i.i
  %v.0.i.i = load ptr, ptr %3, align 8, !noalias !52, !nonnull !28, !noundef !28
  call void @llvm.lifetime.end.p0(ptr nonnull %self3.i.i), !noalias !52
  store ptr %v.0.i.i, ptr %1, align 8, !alias.scope !52
  %6 = icmp sgt i64 %..i16.i.i, -1
  tail call void @llvm.assume(i1 %6)
  store i64 %..i16.i.i, ptr %v, align 8, !alias.scope !52
  %.pre = sub i64 %..i16.i.i, %_6
  %7 = icmp ult i64 %.pre, 3
  tail call void @llvm.experimental.noalias.scope.decl(metadata !53)
  br i1 %7, label %bb1.i.i, label %_RINvMsk_NtCsbrQcgdVahqB_5alloc3vecINtB6_3VechE14extend_trustedINtNtNtCs9cuWXJ791ES_4core5array4iter8IntoIterhKj3_EECseHTl9kyFgP7_18vec_reserve_extend.exit, !prof !56

bb1.i.i:                                          ; preds = %_RNvMNtCs9cuWXJ791ES_4core6resultINtB2_6ResultuNtNtCsbrQcgdVahqB_5alloc11collections15TryReserveErrorE6unwrapCseHTl9kyFgP7_18vec_reserve_extend.exit
; call <alloc::raw_vec::RawVecInner<_>>::reserve::do_reserve_and_handle::<alloc::alloc::Global>
  tail call fastcc void @_RINvNvMs2_NtCsbrQcgdVahqB_5alloc7raw_vecINtB8_11RawVecInnerpE7reserve21do_reserve_and_handleNtNtBa_5alloc6GlobalECseHTl9kyFgP7_18vec_reserve_extend(ptr noalias nofree noundef nonnull align 8 dereferenceable(24) %v, i64 noundef %_6, i64 noundef 3)
  %_27.pre.i = load i64, ptr %0, align 8, !alias.scope !53, !noalias !57
  br label %_RINvMsk_NtCsbrQcgdVahqB_5alloc3vecINtB6_3VechE14extend_trustedINtNtNtCs9cuWXJ791ES_4core5array4iter8IntoIterhKj3_EECseHTl9kyFgP7_18vec_reserve_extend.exit

_RINvMsk_NtCsbrQcgdVahqB_5alloc3vecINtB6_3VechE14extend_trustedINtNtNtCs9cuWXJ791ES_4core5array4iter8IntoIterhKj3_EECseHTl9kyFgP7_18vec_reserve_extend.exit: ; preds = %start, %bb1.i.i, %_RNvMNtCs9cuWXJ791ES_4core6resultINtB2_6ResultuNtNtCsbrQcgdVahqB_5alloc11collections15TryReserveErrorE6unwrapCseHTl9kyFgP7_18vec_reserve_extend.exit
  %_27.i = phi i64 [ %_27.pre.i, %bb1.i.i ], [ %_6, %_RNvMNtCs9cuWXJ791ES_4core6resultINtB2_6ResultuNtNtCsbrQcgdVahqB_5alloc11collections15TryReserveErrorE6unwrapCseHTl9kyFgP7_18vec_reserve_extend.exit ], [ %_6, %start ]
  %8 = getelementptr inbounds nuw i8, ptr %v, i64 8
  %_26.i = load ptr, ptr %8, align 8, !alias.scope !53, !noalias !57, !nonnull !28, !noundef !28
  %scevgep.i.i.i = getelementptr i8, ptr %_26.i, i64 %_27.i
  store i8 1, ptr %scevgep.i.i.i, align 1, !noalias !59
  %_8.sroa.6.16.scevgep.i.i.i.sroa_idx = getelementptr inbounds nuw i8, ptr %scevgep.i.i.i, i64 1
  store i8 2, ptr %_8.sroa.6.16.scevgep.i.i.i.sroa_idx, align 1, !noalias !59
  %_8.sroa.7.16.scevgep.i.i.i.sroa_idx = getelementptr inbounds nuw i8, ptr %scevgep.i.i.i, i64 2
  store i8 3, ptr %_8.sroa.7.16.scevgep.i.i.i.sroa_idx, align 1, !noalias !59
  %9 = add i64 %_27.i, 3
  store i64 %9, ptr %0, align 8, !alias.scope !53, !noalias !69
  ret void
}

Start with tests/codegen-llvm/vec-reserve-extend.rs and run the failing codegen-LLVM test to reproduce the CHECK-NOT failure. Compare the generated IR with the behavior introduced by llvm/llvm-project@7a3aa7da4c02, then determine whether the test expectation or Rust-side LLVM guidance is incorrect. Done means the test passes on LLVM 24 with the intended single-reserve behavior validated.