[llvm-branch-commits] [llvm] release/21.x: [NVPTX] Disable relative lookup tables (#159748) (PR #160064)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/160064

Backport 1ed15374638ecf6046169194b4b3ca34b7cf340f

Requested by: @nikic

>From 2c30e1b9e92b47e642007efc3b0b72c54d0c7063 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Mon, 22 Sep 2025 12:18:25 +0200
Subject: [PATCH] [NVPTX] Disable relative lookup tables (#159748)

Relative lookup tables result in "LLVM ERROR: Circular dependency found
in global variable set", so disable them for this target.

(cherry picked from commit 1ed15374638ecf6046169194b4b3ca34b7cf340f)
---
 .../Target/NVPTX/NVPTXTargetTransformInfo.h   |  5 +++
 .../RelLookupTableConverter/nvptx.ll          | 32 +++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 llvm/test/Transforms/RelLookupTableConverter/nvptx.ll

diff --git a/llvm/lib/Target/NVPTX/NVPTXTargetTransformInfo.h b/llvm/lib/Target/NVPTX/NVPTXTargetTransformInfo.h
index 9a6e261c811a0..437edfb8ffc75 100644
--- a/llvm/lib/Target/NVPTX/NVPTXTargetTransformInfo.h
+++ b/llvm/lib/Target/NVPTX/NVPTXTargetTransformInfo.h
@@ -183,6 +183,11 @@ class NVPTXTTIImpl final : public BasicTTIImplBase<NVPTXTTIImpl> {
   void collectKernelLaunchBounds(
       const Function &F,
       SmallVectorImpl<std::pair<StringRef, int64_t>> &LB) const override;
+
+  bool shouldBuildRelLookupTables() const override {
+    // Self-referential globals are not supported.
+    return false;
+  }
 };
 
 } // end namespace llvm
diff --git a/llvm/test/Transforms/RelLookupTableConverter/nvptx.ll b/llvm/test/Transforms/RelLookupTableConverter/nvptx.ll
new file mode 100644
index 0000000000000..70ebf220c369c
--- /dev/null
+++ b/llvm/test/Transforms/RelLookupTableConverter/nvptx.ll
@@ -0,0 +1,32 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
+; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -S | FileCheck %s
+; REQUIRES: nvptx-registered-target
+target triple = "nvptx64-nvidia-cuda"
+
+; Do not produce relative lookup table for nvptx target.
+
+ at a1 = internal constant i32 0, align 4
+ at b1 = internal constant i32 0, align 4
+ at c1 = internal constant i32 0, align 4
+ at d1 = internal constant i32 0, align 4
+
+ at switch.table = private unnamed_addr constant [3 x ptr] [ptr @a1, ptr @b1, ptr @c1], align 8
+
+;.
+; CHECK: @a1 = internal constant i32 0, align 4
+; CHECK: @b1 = internal constant i32 0, align 4
+; CHECK: @c1 = internal constant i32 0, align 4
+; CHECK: @d1 = internal constant i32 0, align 4
+; CHECK: @switch.table = private unnamed_addr constant [3 x ptr] [ptr @a1, ptr @b1, ptr @c1], align 8
+;.
+define ptr @internal_linkage(i32 %cond) {
+; CHECK-LABEL: define ptr @internal_linkage(
+; CHECK-SAME: i32 [[COND:%.*]]) {
+; CHECK-NEXT:    [[SWITCH_GEP:%.*]] = getelementptr inbounds [3 x ptr], ptr @switch.table, i32 0, i32 [[COND]]
+; CHECK-NEXT:    [[RELTABLE_INTRINSIC:%.*]] = load ptr, ptr [[SWITCH_GEP]], align 8
+; CHECK-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+  %switch.gep = getelementptr inbounds [3 x ptr], ptr @switch.table, i32 0, i32 %cond
+  %switch.load = load ptr, ptr %switch.gep, align 8
+  ret ptr %switch.load
+}