[llvm] [DAGCombiner] In mergeTruncStore, make sure we aren't storing shifted in bits. (PR #90939)

[Matt Arsenault via llvm-commits]

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@@ -485,6 +485,11 @@ RISCVISAInfo::parseNormalizedArchString(StringRef Arch) {
     if (MajorVersionStr.getAsInteger(10, MajorVersion))
       return createStringError(errc::invalid_argument,
                                "failed to parse major version number");
+
+    if (ExtName[0] == 'z' && (ExtName.size() == 1 || isDigit(ExtName[1])))
+      return createStringError(errc::invalid_argument,
+                               "'z' must be followed by a letter");
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arsenm wrote:

Unrelated change 

https://github.com/llvm/llvm-project/pull/90939