[clang] [llvm] [WebAssembly] Add `-i128:128` to the `datalayout` string. (PR #119204)

[via llvm-commits]

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@@ -183,11 +183,12 @@ class LLVM_LIBRARY_VISIBILITY WebAssembly32TargetInfo
                                    const TargetOptions &Opts)
       : WebAssemblyTargetInfo(T, Opts) {
     if (T.isOSEmscripten())
-      resetDataLayout("e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-f128:64-n32:64-"
-                      "S128-ni:1:10:20");
-    else
       resetDataLayout(
-          "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20");
+          "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-f128:64-n32:64-"
+          "S128-ni:1:10:20");
+    else
+      resetDataLayout("e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-n32:64-"
+                      "S128-ni:1:10:20");
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workingjubilee wrote:

while a preexisting concern and thus not something that should be held against this PR, it seems slightly unfortunate that so many LLVM targets use `resetDataLayout`. It's not that I think that overriding the string is a good idea. Rather, ignoring it makes the ability to set a data-layout string in an LLVM module merely an attractive nuisance rather than something with actual utility.

I was going to try to use Compiler Explorer's pass-level diffing view of the LLVM pipeline to see where the fold that @dschuff noticed was introduced, but that uses a precompiled LLVM, so it won't have this change. The easiest way to introduce the modified data-layout to a precompiled LLVM would be a module-level string, but that seems to do nothing.

I could bother to rebuild LLVM and do things in a much more manual way, of course, but then what is the ability to pass the string in the module even for?

https://github.com/llvm/llvm-project/pull/119204