[llvm] [SPIR-V] Add OpSMulExtended and OpUMulExtended builtin support (PR #187474)

[Dmitry Sidorov via llvm-commits]

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@@ -1996,6 +1996,97 @@ static bool generateICarryBorrowInst(const SPIRV::IncomingCall *Call,
   return true;
 }
 
+// We expect a builtin in one of two forms:
+//
+//  (1) sret convention (3 arguments):
+//     void Name(ptr sret([RetType]) %result, Type %operand1, Type %operand2)
+//     =>  Res = Opcode RetType Operand1 Operand2
+//         OpStore %result Res
+//
+//  (2) direct return convention (2 arguments):
+//     RetType Name(Type %operand1, Type %operand2)
+//     =>  Res = Opcode RetType Operand1 Operand2
+//
+// RetType is a struct with two members of the same type as the operands.
+static bool generateMulExtendedInst(const SPIRV::IncomingCall *Call,
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MrSidims wrote:

I feel like that sret path here is essentially the same as for generateICarryBorrowInst. Can they be unified? 

https://github.com/llvm/llvm-project/pull/187474