[FastIsel] Get the right register type for call instruction (#164565)

When switch from fast isel to dag isel the input value is from llvm IR
instruction.
If the instruction is call we should get the calling convention of the
callee and
pass it to RegsForValue::getCopyFromRegs, so that it can deduce the
right RegisterVT
of the returned value of the callee.

---------

Co-authored-by: Yuanke Luo <[email protected]>

Author: LuoYuanke

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -1977,8 +1977,13 @@ SDValue SelectionDAGBuilder::getValueImpl(const Value *V) {
   if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
     Register InReg = FuncInfo.InitializeRegForValue(Inst);
 
+    std::optional<CallingConv::ID> CallConv;
+    auto *CI = dyn_cast<CallInst>(Inst);
+    if (CI && !CI->isInlineAsm())
+      CallConv = CI->getCallingConv();
+
     RegsForValue RFV(*DAG.getContext(), TLI, DAG.getDataLayout(), InReg,
-                     Inst->getType(), std::nullopt);
+                     Inst->getType(), CallConv);
     SDValue Chain = DAG.getEntryNode();
     return RFV.getCopyFromRegs(DAG, FuncInfo, getCurSDLoc(), Chain, nullptr, V);
   }

llvm/test/CodeGen/X86/bf16-fast-isel.ll

@@ -0,0 +1,66 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; RUN: llc --fast-isel < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
+
+define i8 @test_direct_call(ptr %f) nounwind {
+; CHECK-LABEL: test_direct_call:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    callq foo@PLT
+; CHECK-NEXT:    callq bar@PLT
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+entry:
+  %call = call bfloat @foo(ptr %f)
+  %call2 = call zeroext i8 @bar(bfloat %call)
+  ret i8 %call2
+}
+
+define i8 @test_fast_direct_call(ptr %f) nounwind {
+; CHECK-LABEL: test_fast_direct_call:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    callq foo_fast@PLT
+; CHECK-NEXT:    callq bar@PLT
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+entry:
+  %call = call fastcc bfloat @foo_fast(ptr %f)
+  %call2 = call zeroext i8 @bar(bfloat %call)
+  ret i8 %call2
+}
+
+define i8 @test_indirect_all(ptr %fptr, ptr %f) nounwind {
+; CHECK-LABEL: test_indirect_all:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushq %rbx
+; CHECK-NEXT:    movq %rdi, %rbx
+; CHECK-NEXT:    movq %rsi, %rdi
+; CHECK-NEXT:    callq foo@PLT
+; CHECK-NEXT:    callq *%rbx
+; CHECK-NEXT:    popq %rbx
+; CHECK-NEXT:    retq
+entry:
+  %call = call bfloat @foo(ptr %f)
+  %call2 = call zeroext i8 %fptr(bfloat %call)
+  ret i8 %call2
+}
+
+define i8 @test_fast_indirect_all(ptr %fptr, ptr %f) nounwind {
+; CHECK-LABEL: test_fast_indirect_all:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushq %rbx
+; CHECK-NEXT:    movq %rdi, %rbx
+; CHECK-NEXT:    movq %rsi, %rdi
+; CHECK-NEXT:    callq foo@PLT
+; CHECK-NEXT:    callq *%rbx
+; CHECK-NEXT:    popq %rbx
+; CHECK-NEXT:    retq
+entry:
+  %call = call fastcc bfloat @foo(ptr %f)
+  %call2 = call zeroext i8 %fptr(bfloat %call)
+  ret i8 %call2
+}
+
+declare bfloat @foo(ptr %f)
+declare zeroext i8 @bar(bfloat)
+declare fastcc bfloat @foo_fast(ptr %f)