[llvm] DAG: Check libcall function is supported before emission (PR #144314)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/144314

Whether the libcall implementation is supported should always
be checked before emission. Previously this would emit a call
to a non-existent function, and then since r600 doesn't support
calls it would error on the call. This switches it to a direct
legalization failure.

Also swap to use reportFatalInternalError. Probably should
be reportFatalUsageError; we don't want a backtrace and this will
never be fixed, but it is tested.

>From eb50e736c24f5019812fedc83aeac11b178dc729 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Mon, 16 Jun 2025 17:04:59 +0900
Subject: [PATCH] DAG: Check libcall function is supported before emission

Whether the libcall implementation is supported should always
be checked before emission. Previously this would emit a call
to a non-existent function, and then since r600 doesn't support
calls it would error on the call. This switches it to a direct
legalization failure.

Also swap to use reportFatalInternalError. Probably should
be reportFatalUsageError; we don't want a backtrace and this will
never be fixed, but it is tested.
---
 llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp | 10 ++++++----
 llvm/test/CodeGen/AMDGPU/fneg.ll                 |  4 +++-
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index a0ffb4b6d5a4c..1be61e4b86af2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -178,10 +178,12 @@ TargetLowering::makeLibCall(SelectionDAG &DAG, RTLIB::Libcall LC, EVT RetVT,
     Args.push_back(Entry);
   }
 
-  if (LC == RTLIB::UNKNOWN_LIBCALL)
-    report_fatal_error("Unsupported library call operation!");
-  SDValue Callee = DAG.getExternalSymbol(getLibcallName(LC),
-                                         getPointerTy(DAG.getDataLayout()));
+  const char *LibcallName = getLibcallName(LC);
+  if (LC == RTLIB::UNKNOWN_LIBCALL || !LibcallName)
+    reportFatalInternalError("unsupported library call operation");
+
+  SDValue Callee =
+      DAG.getExternalSymbol(LibcallName, getPointerTy(DAG.getDataLayout()));
 
   Type *RetTy = RetVT.getTypeForEVT(*DAG.getContext());
   TargetLowering::CallLoweringInfo CLI(DAG);
diff --git a/llvm/test/CodeGen/AMDGPU/fneg.ll b/llvm/test/CodeGen/AMDGPU/fneg.ll
index 7262724064918..c3f4ebe30152b 100644
--- a/llvm/test/CodeGen/AMDGPU/fneg.ll
+++ b/llvm/test/CodeGen/AMDGPU/fneg.ll
@@ -3,7 +3,9 @@
 ; RUN: llc -mtriple=amdgcn -mcpu=tonga < %s | FileCheck -enable-var-scope -check-prefixes=GCN,VI %s
 ; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=+real-true16 < %s | FileCheck -enable-var-scope -check-prefixes=GCN,GFX11,GFX11-TRUE16 %s
 ; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=-real-true16 < %s | FileCheck -enable-var-scope -check-prefixes=GCN,GFX11,GFX11-FAKE16 %s
-; RUN: not llc -mtriple=r600 -mcpu=redwood < %s
+; RUN: not --crash llc -mtriple=r600 -mcpu=redwood < %s 2>&1 | FileCheck -check-prefix=R600-ERR %s
+
+; R600-ERR: LLVM ERROR: unsupported library call operation
 
 define amdgpu_kernel void @s_fneg_f32(ptr addrspace(1) %out, float %in) {
 ; SI-LABEL: s_fneg_f32: