[llvm] [LLVM][IR] Add textual shorthand for specifying constant vector splats. (PR #74620)

[Paul Walker via llvm-commits]

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@@ -3981,6 +3981,33 @@ bool LLParser::parseValID(ValID &ID, PerFunctionState *PFS, Type *ExpectedTy) {
     return false;
   }
 
+  case lltok::kw_splat: {
+    Lex.Lex();
+    if (parseToken(lltok::lparen, "expected '(' after vector splat"))
+      return true;
+    Constant *C;
+    if (parseGlobalTypeAndValue(C))
+      return true;
+    if (parseToken(lltok::rparen, "expected ')' at end of vector splat"))
+      return true;
+
+    if (auto *CI = dyn_cast<ConstantInt>(C)) {
+      ID.APSIntVal = CI->getValue();
+      ID.Kind = ValID::t_APSInt;
+      return false;
+    }
+
+    if (auto *CFP = dyn_cast<ConstantFP>(C)) {
+      ID.APFloatVal = CFP->getValue();
+      ID.Kind = ValID::t_APFloat;
+      return false;
+    }
+
+    ID.ConstantVal = C;
+    ID.Kind = ValID::t_Constant;
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paulwalker-arm wrote:

As above.  Constants are parsed, stashed in a `ValID` union and the various Constant classes are create afterwords once the type is known.

https://github.com/llvm/llvm-project/pull/74620