[CodeGen] Fix ConvertNodeToLibcall for STRICT_FPOWI

[xiangzhangllvm]

Summary

Correct the Operand index when convert STRICT_FPOWI to FPOW.
(the old code miss considering the chain operand of STRICT_FPOWI, will cause crash.)

[pengfei]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4100–4101

We should generate STRICT_SINT_TO_FP and STRICT_FPOWI for strict node and push the output chain into Results.

[xiangzhangllvm]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4100–4101

Here is already STRICT_FPOWI, and the Target has no libcall for STRICT_FPOWI

[pengfei]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4100–4101

Oh, I meant STRICT_FPOW...

[xiangzhangllvm]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4100–4101

En., Make sense : )

[xiangzhangllvm]

Address pengfei's comment.

[pengfei]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4106–4109

You still need to push the chain, like line 3870.

llvm/test/CodeGen/X86/float-strict-powi-convert.ll

3

We don't use it anymore.

[xiangzhangllvm]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4106–4109

good catch!

llvm/test/CodeGen/X86/float-strict-powi-convert.ll

3

Not use what ? the windows check is needed to meet the if condition ( line 4101 if (Node->isStrictFPOpcode()))

[pengfei]

llvm/test/CodeGen/X86/float-strict-powi-convert.ll

3

-disable-strictnode-mutation. X86 supports strict FP by default. This option is used for targets only support it partly.

[xiangzhangllvm]

Address pengfei's comment

[pengfei]

LGTM.

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

ExpandFPLibCall(Node, RTLIB::ROUNDEVEN_F32,
                     RTLIB::ROUNDEVEN_F128,
                     RTLIB::ROUNDEVEN_PPCF128, Results);
     break;
   case ISD::FPOWI:
   case ISD::STRICT_FPOWI: {
     RTLIB::Libcall LC = RTLIB::getPOWI(Node->getSimpleValueType(0));
     assert(LC != RTLIB::UNKNOWN_LIBCALL && "Unexpected fpowi.");
     if (!TLI.getLibcallName(LC)) {
       // Some targets don't have a powi libcall; use pow instead.
-      SDValue Exponent = DAG.getNode(ISD::SINT_TO_FP, SDLoc(Node),
-                                     Node->getValueType(0),
-                                     Node->getOperand(1));
+      if (Node->isStrictFPOpcode()) {
+        SDValue Exponent =
+            DAG.getNode(ISD::STRICT_SINT_TO_FP, SDLoc(Node),
+                        {Node->getValueType(0), Node->getValueType(1)},
+                        {Node->getOperand(0), Node->getOperand(2)});
+        SDValue FPOW =
+            DAG.getNode(ISD::STRICT_FPOW, SDLoc(Node),
+                        {Node->getValueType(0), Node->getValueType(1)},
+                        {Exponent.getValue(1), Node->getOperand(1), Exponent});
+        Results.push_back(FPOW);
+        Results.push_back(FPOW.getValue(1));
+      } else {
+        SDValue Exponent =
+            DAG.getNode(ISD::SINT_TO_FP, SDLoc(Node), Node->getValueType(0),
         Results.push_back(DAG.getNode(ISD::FPOW, SDLoc(Node),
-                                    Node->getValueType(0), Node->getOperand(0),
-                                    Exponent));
+                                      Node->getValueType(0),
+                                      Node->getOperand(0), Exponent));
+      }
       break;
     }
     unsigned Offset = Node->isStrictFPOpcode() ? 1 : 0;
     bool ExponentHasSizeOfInt =
         DAG.getLibInfo().getIntSize() ==
         Node->getOperand(1 + Offset).getValueType().getSizeInBits();
     if (!ExponentHasSizeOfInt) {
       // If the exponent does not match with sizeof(int) a libcall to

llvm/test/CodeGen/X86/float-strict-powi-convert.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=x86_64-pc-windows-msvc %s -o - | FileCheck %s -check-prefix=WIN
+; RUN: llc -mtriple=x86_64-pc-linux %s -o -| FileCheck %s -check-prefix=UNIX
+
+declare float @llvm.experimental.constrained.powi.f32.i32(float, i32, metadata, metadata)
+
+define float @powi_f64(float %a, i32 %b) nounwind strictfp {
+; WIN-LABEL: powi_f64:
+; WIN:       # %bb.0:
+; WIN-NEXT:    subq $40, %rsp
+; WIN-NEXT:    cvtsi2ss %edx, %xmm1
+; WIN-NEXT:    callq powf
+; WIN-NEXT:    addq $40, %rsp
+; WIN-NEXT:    retq
+;
+; UNIX-LABEL: powi_f64:
+; UNIX:       # %bb.0:
+; UNIX-NEXT:    pushq %rax
+; UNIX-NEXT:    callq __powisf2@PLT
+; UNIX-NEXT:    popq %rax
+; UNIX-NEXT:    retq
+  %1 = call float @llvm.experimental.constrained.powi.f32.i32(float %a, i32 %b, metadata !"round.tonearest", metadata !"fpexcept.ignore") strictfp
+  ret float %1
+}