From 51ebca085c77f312b33be69021c6bc795ad3271b Mon Sep 17 00:00:00 2001
From: Artem Belevich <tra@google.com>
Date: Fri, 14 Dec 2018 23:53:06 +0000
Subject: [PATCH] [NVPTX] Lower instructions that expand into libcalls.

The change is an effort to split and refactor abandoned
D34708 into smaller parts.

Here the behaviour of unsupported instructions is changed
to match the behaviour of explicit intrinsics calls.
Currently LLVM crashes with:
> Assertion getInstruction() && "Not a call or invoke instruction!" failed.

With this patch LLVM produces a more sensible error message:
> Cannot select: ... i32 = ExternalSymbol'__foobar'

Author: Denys Zariaiev <denys.zariaiev@gmail.com>

Differential Revision: https://reviews.llvm.org/D55145

llvm-svn: 349213
---
 lib/Target/NVPTX/NVPTXISelLowering.cpp    | 13 +++++++++----
 test/CodeGen/NVPTX/libcall-instruction.ll |  8 ++++++++
 2 files changed, 17 insertions(+), 4 deletions(-)
 create mode 100644 test/CodeGen/NVPTX/libcall-instruction.ll

diff --git a/lib/Target/NVPTX/NVPTXISelLowering.cpp b/lib/Target/NVPTX/NVPTXISelLowering.cpp
index eceb4fc6d88..5c16c34e21d 100644
--- a/lib/Target/NVPTX/NVPTXISelLowering.cpp
+++ b/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -1661,7 +1661,12 @@ SDValue NVPTXTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     }
   }
 
-  if (!Func) {
+  // Both indirect calls and libcalls have nullptr Func. In order to distinguish
+  // between them we must rely on the call site value which is valid for
+  // indirect calls but is always null for libcalls.
+  bool isIndirectCall = !Func && CS;
+
+  if (isIndirectCall) {
     // This is indirect function call case : PTX requires a prototype of the
     // form
     // proto_0 : .callprototype(.param .b32 _) _ (.param .b32 _);
@@ -1685,7 +1690,7 @@ SDValue NVPTXTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     Chain, DAG.getConstant((Ins.size() == 0) ? 0 : 1, dl, MVT::i32), InFlag
   };
   // We model convergent calls as separate opcodes.
-  unsigned Opcode = Func ? NVPTXISD::PrintCallUni : NVPTXISD::PrintCall;
+  unsigned Opcode = isIndirectCall ? NVPTXISD::PrintCall : NVPTXISD::PrintCallUni;
   if (CLI.IsConvergent)
     Opcode = Opcode == NVPTXISD::PrintCallUni ? NVPTXISD::PrintConvergentCallUni
                                               : NVPTXISD::PrintConvergentCall;
@@ -1719,12 +1724,12 @@ SDValue NVPTXTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   }
   SDVTList CallArgEndVTs = DAG.getVTList(MVT::Other, MVT::Glue);
   SDValue CallArgEndOps[] = { Chain,
-                              DAG.getConstant(Func ? 1 : 0, dl, MVT::i32),
+                              DAG.getConstant(isIndirectCall ? 0 : 1, dl, MVT::i32),
                               InFlag };
   Chain = DAG.getNode(NVPTXISD::CallArgEnd, dl, CallArgEndVTs, CallArgEndOps);
   InFlag = Chain.getValue(1);
 
-  if (!Func) {
+  if (isIndirectCall) {
     SDVTList PrototypeVTs = DAG.getVTList(MVT::Other, MVT::Glue);
     SDValue PrototypeOps[] = { Chain,
                                DAG.getConstant(uniqueCallSite, dl, MVT::i32),
diff --git a/test/CodeGen/NVPTX/libcall-instruction.ll b/test/CodeGen/NVPTX/libcall-instruction.ll
new file mode 100644
index 00000000000..0c2cab7eaa5
--- /dev/null
+++ b/test/CodeGen/NVPTX/libcall-instruction.ll
@@ -0,0 +1,8 @@
+; RUN: not llc < %s -march=nvptx 2>&1 | FileCheck %s
+; used to panic on failed assetion and now fails with a "Cannot select"
+
+; CHECK: LLVM ERROR: Cannot select: {{t28|0x[0-9a-f]+}}: i32 = ExternalSymbol'__umodti3'
+define hidden i128 @remainder(i128, i128) {
+  %3 = urem i128 %0, %1
+  ret i128 %3
+}