[llvm] [llvm][CodeGen] Intrinsic `llvm.powi/ldexp.*` code gen for vector arguments (PR #118242)

[Matt Arsenault via llvm-commits]

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@@ -2585,6 +2585,8 @@ SDValue DAGTypeLegalizer::PromoteIntOp_ExpOp(SDNode *N) {
                              : RTLIB::getLDEXP(N->getValueType(0));
 
   if (LC == RTLIB::UNKNOWN_LIBCALL || !TLI.getLibcallName(LC)) {
+    if (N->getValueType(0).isVector())
+      return DAG.UnrollVectorOp(N);
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arsenm wrote:

makeLibCall should really be looking at the signature of the underlying call, but RuntimeLibcalls currently does not record this information. TargetLibraryInfo does, which is separate for some reason. This keeps coming up as a problem, these really need to be merged in some way (cc @jhuber6).

Taking the type from the DAG node isn't strictly correct, it's just where we've ended up. This came up recently for the special case in ExpandFPLibCall to sign extend the integer argument for FLDEXP. 

Practically speaking, I don't think any targets will have a vector powi implementation (I at least don't see any in RuntimeLibcalls), so unrolling works out. I guess this could get a fixme and go ahead for now, but it's still a hack 

https://github.com/llvm/llvm-project/pull/118242