[llvm] [PowerPC][CodeGen] Expand ISD::AssertNoFPClass for ppc_fp128 (PR #152357)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-powerpc

Author: Amy Kwan (amy-kwan)

<details>
<summary>Changes</summary>

780054d3ff18075a6bc433029f336931792b1d2d added support for `ISD::AssertNoFPClass`.

This ISD node can be used with the `ppc_fp128` type, which is really just two `f64s` and requires expanding when used with `ISD::AssertNoFPClass`. Without the support for expanding the result, we get an assertion because the legalizer does not know how to expand the results of `ppc_fp128` with `ISD::AssertNoFPClass`.
```
ExpandFloatResult #<!-- -->0: t7: ppcf128 = AssertNoFPClass t5, TargetConstant:i32<3>

LLVM ERROR: Do not know how to expand the result of this operator!
```
Thus, this patch aims to add support for the expand so we no longer assert.

This fixes #<!-- -->151375.

---
Full diff: https://github.com/llvm/llvm-project/pull/152357.diff


3 Files Affected:

- (modified) llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp (+9) 
- (modified) llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h (+1) 
- (added) llvm/test/CodeGen/PowerPC/nofpclass.ll (+13) 


``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
index 2cad36eff9c88..8140c0e771a7b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
@@ -1551,6 +1551,7 @@ void DAGTypeLegalizer::ExpandFloatResult(SDNode *N, unsigned ResNo) {
   case ISD::VAARG:              ExpandRes_VAARG(N, Lo, Hi); break;
 
   case ISD::ConstantFP: ExpandFloatRes_ConstantFP(N, Lo, Hi); break;
+  case ISD::AssertNoFPClass: ExpandFloatRes_AssertNoFPClass(N, Lo, Hi); break;
   case ISD::FABS:       ExpandFloatRes_FABS(N, Lo, Hi); break;
   case ISD::STRICT_FMINNUM:
   case ISD::FMINNUM:    ExpandFloatRes_FMINNUM(N, Lo, Hi); break;
@@ -1966,6 +1967,14 @@ void DAGTypeLegalizer::ExpandFloatRes_FNEG(SDNode *N, SDValue &Lo,
   Hi = DAG.getNode(ISD::FNEG, dl, Hi.getValueType(), Hi);
 }
 
+void DAGTypeLegalizer::ExpandFloatRes_AssertNoFPClass(SDNode *N, SDValue &Lo,
+                                                      SDValue &Hi) {
+  SDLoc dl(N);
+  GetExpandedFloat(N->getOperand(0), Lo, Hi);
+  Lo = DAG.getNode(ISD::AssertNoFPClass, dl, Lo.getValueType(), Lo);
+  Hi = DAG.getNode(ISD::AssertNoFPClass, dl, Hi.getValueType(), Hi);
+}
+
 void DAGTypeLegalizer::ExpandFloatRes_FP_EXTEND(SDNode *N, SDValue &Lo,
                                                 SDValue &Hi) {
   EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
index 63544e63e1da1..33fa3012618b3 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
@@ -681,6 +681,7 @@ class LLVM_LIBRARY_VISIBILITY DAGTypeLegalizer {
       SDNode *N, RTLIB::Libcall LC, std::optional<unsigned> CallRetResNo = {});
 
   // clang-format off
+  void ExpandFloatRes_AssertNoFPClass(SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandFloatRes_FABS      (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandFloatRes_FACOS     (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandFloatRes_FASIN     (SDNode *N, SDValue &Lo, SDValue &Hi);
diff --git a/llvm/test/CodeGen/PowerPC/nofpclass.ll b/llvm/test/CodeGen/PowerPC/nofpclass.ll
new file mode 100644
index 0000000000000..444e62cbbcffc
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/nofpclass.ll
@@ -0,0 +1,13 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -verify-machineinstrs  -mtriple=powerpc64le-unknown-linux-gnu < %s \
+; RUN:   | FileCheck %s
+; RUN: llc -verify-machineinstrs  -mtriple=powerpc64-ibm-aix-xcoff < %s \
+; RUN:   | FileCheck %s
+
+define ppc_fp128 @f(ppc_fp128 nofpclass(nan) %s) {
+; CHECK-LABEL: f:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    blr
+entry:
+  ret ppc_fp128 %s
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/152357