Update the data layout.

Recent NVVM IR docs (e.g.
https://docs.nvidia.com/cuda/archive/13.0.0/nvvm-ir-spec/index.html#data-layout)
mention four data layouts, which I will abbreviate as:
- 64-bit-with-128-bit-integers
- 32-bit-with-128-bit-integers
- 64-bit-without-128-bit-integers
- 32-bit-without-128-bit-integers

These docs have said the same thing for every CUDA version from 12.0 to 13.0:
- 64-bit-with-128-bit-integers is "supported".
- The others are "deprecated and will be removed in a future release".

We currently use 64-bit-without-128-bit integers. This works fine on
CUDA 12.8, but doesn't work on CUDA 13.0 -- libNVVM spits out
"DataLayoutError: Unsupported integer alignment". Even though the docs
haven't changed, 13.0 seems to be the first version actually enforcing
the deprecation. (Or maybe "deprecated" has become "removed" and the
docs haven't caught up, given that there's no apparent way to avoid the
error.)

This commit changes our data layout from 64-bit-without-128-bit-integers
to 64-bit-with-128-bit-integers. This lets commands like `cargo run -p
compiletests -- --target-arch compute_75` run successfully on my ASUS
GX10 with CUDA 13.0. There appear to be no ill side-effects.

Author: nnethercote

crates/rustc_codegen_nvvm/libintrinsics.bc

@@ -5,7 +5,8 @@
 ; if you update this make sure to update libintrinsics.bc by running llvm-as (make sure you are using llvm-7 or it won't work when
 ; loaded into libnvvm).
 source_filename = "libintrinsics"
-target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+; This data layout must match `DATA_LAYOUT` in `crates/rustc_codegen_nvvm/src/target.rs`.
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-i128:128:128-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
 target triple = "nvptx64-nvidia-cuda"
 
 ; warp ----

crates/rustc_codegen_nvvm/libintrinsics.ll

@@ -3,7 +3,8 @@ use rustc_target::spec::{
     LinkerFlavor, MergeFunctions, PanicStrategy, Target, TargetMetadata, TargetOptions,
 };
 
-pub const DATA_LAYOUT: &str = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64";
+// This data layout must match `datalayout` in `crates/rustc_codegen_nvvm/libintrinsics.ll`.
+pub const DATA_LAYOUT: &str = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-i128:128:128-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64";
 pub const TARGET_TRIPLE: &str = "nvptx64-nvidia-cuda";
 pub const POINTER_WIDTH: u32 = 64;