[llvm-branch-commits] [llvm] use default intrinsic attrs for BPF packet loads (PR #105314)

[Bryce Kahle via llvm-branch-commits]

https://github.com/brycekahle created https://github.com/llvm/llvm-project/pull/105314

The BPF packet load intrinsics lost attribute WillReturn due to 0b20c30. The attribute loss causes excessive bitshifting, resulting in previously working programs failing the BPF verifier due to instruction/complexity limits.

cherry picked only the BPF changes from 99a10f1

>From 95764a1c9dafc13e65bc2794f311ec5ea20f95c0 Mon Sep 17 00:00:00 2001
From: Bryce Kahle <bryce.kahle at datadoghq.com>
Date: Tue, 20 Aug 2024 12:25:33 -0700
Subject: [PATCH] use default intrinsic attrs for BPF packet loads

The BPF packet load intrinsics lost attribute WillReturn due to 0b20c30. The attribute loss causes excessive bitshifting, resulting in previously working programs failing the BPF verifier due to instruction/complexity limits.

cherry picked only the BPF changes from 99a10f1

Signed-off-by: Bryce Kahle <bryce.kahle at datadoghq.com>
---
 llvm/include/llvm/IR/IntrinsicsBPF.td      |  6 ++--
 llvm/test/CodeGen/BPF/sockex2.ll           |  2 +-
 llvm/test/Transforms/DCE/intrinsics-bpf.ll | 33 ++++++++++++++++++++++
 3 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100644 llvm/test/Transforms/DCE/intrinsics-bpf.ll

diff --git a/llvm/include/llvm/IR/IntrinsicsBPF.td b/llvm/include/llvm/IR/IntrinsicsBPF.td
index c7ec0916f1d1f8..d02eaa6d0dff69 100644
--- a/llvm/include/llvm/IR/IntrinsicsBPF.td
+++ b/llvm/include/llvm/IR/IntrinsicsBPF.td
@@ -13,11 +13,11 @@
 // Specialized loads from packet
 let TargetPrefix = "bpf" in {  // All intrinsics start with "llvm.bpf."
   def int_bpf_load_byte : ClangBuiltin<"__builtin_bpf_load_byte">,
-              Intrinsic<[llvm_i64_ty], [llvm_ptr_ty, llvm_i64_ty], [IntrReadMem]>;
+              DefaultAttrsIntrinsic<[llvm_i64_ty], [llvm_ptr_ty, llvm_i64_ty], [IntrReadMem]>;
   def int_bpf_load_half : ClangBuiltin<"__builtin_bpf_load_half">,
-              Intrinsic<[llvm_i64_ty], [llvm_ptr_ty, llvm_i64_ty], [IntrReadMem]>;
+              DefaultAttrsIntrinsic<[llvm_i64_ty], [llvm_ptr_ty, llvm_i64_ty], [IntrReadMem]>;
   def int_bpf_load_word : ClangBuiltin<"__builtin_bpf_load_word">,
-              Intrinsic<[llvm_i64_ty], [llvm_ptr_ty, llvm_i64_ty], [IntrReadMem]>;
+              DefaultAttrsIntrinsic<[llvm_i64_ty], [llvm_ptr_ty, llvm_i64_ty], [IntrReadMem]>;
   def int_bpf_pseudo : ClangBuiltin<"__builtin_bpf_pseudo">,
               Intrinsic<[llvm_i64_ty], [llvm_i64_ty, llvm_i64_ty]>;
   def int_bpf_preserve_field_info : ClangBuiltin<"__builtin_bpf_preserve_field_info">,
diff --git a/llvm/test/CodeGen/BPF/sockex2.ll b/llvm/test/CodeGen/BPF/sockex2.ll
index 4131d9dac31d88..b1264099f64c60 100644
--- a/llvm/test/CodeGen/BPF/sockex2.ll
+++ b/llvm/test/CodeGen/BPF/sockex2.ll
@@ -311,7 +311,7 @@ flow_dissector.exit.thread:                       ; preds = %86, %12, %196, %199
 ; CHECK-LABEL: bpf_prog2:
 ; CHECK: r0 = *(u16 *)skb[12] # encoding: [0x28,0x00,0x00,0x00,0x0c,0x00,0x00,0x00]
 ; CHECK: r0 = *(u16 *)skb[16] # encoding: [0x28,0x00,0x00,0x00,0x10,0x00,0x00,0x00]
-; CHECK: implicit-def: $r8
+; CHECK: implicit-def: $r7
 ; CHECK: r1 =
 ; CHECK: call 1 # encoding: [0x85,0x00,0x00,0x00,0x01,0x00,0x00,0x00]
 ; CHECK: call 2 # encoding: [0x85,0x00,0x00,0x00,0x02,0x00,0x00,0x00]
diff --git a/llvm/test/Transforms/DCE/intrinsics-bpf.ll b/llvm/test/Transforms/DCE/intrinsics-bpf.ll
new file mode 100644
index 00000000000000..135588ba21cbb1
--- /dev/null
+++ b/llvm/test/Transforms/DCE/intrinsics-bpf.ll
@@ -0,0 +1,33 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S < %s -passes=dce  | FileCheck %s
+
+declare i64 @llvm.bpf.load.half(ptr, i64)
+declare i64 @llvm.bpf.load.word(ptr, i64)
+declare i64 @llvm.bpf.load.byte(ptr, i64)
+
+define void @test_bpf_load_half(ptr %a, i64 %b) {
+; CHECK-LABEL: define void @test_bpf_load_half(
+; CHECK-SAME: ptr [[A:%.*]], i64 [[B:%.*]]) {
+; CHECK-NEXT:    ret void
+;
+  %v = call i64 @llvm.bpf.load.half(ptr %a, i64 %b)
+  ret void
+}
+
+define void @test_bpf_load_word(ptr %a, i64 %b) {
+; CHECK-LABEL: define void @test_bpf_load_word(
+; CHECK-SAME: ptr [[A:%.*]], i64 [[B:%.*]]) {
+; CHECK-NEXT:    ret void
+;
+  %v = call i64 @llvm.bpf.load.word(ptr %a, i64 %b)
+  ret void
+}
+
+define void @test_bpf_load_byte(ptr %a, i64 %b) {
+; CHECK-LABEL: define void @test_bpf_load_byte(
+; CHECK-SAME: ptr [[A:%.*]], i64 [[B:%.*]]) {
+; CHECK-NEXT:    ret void
+;
+  %v = call i64 @llvm.bpf.load.byte(ptr %a, i64 %b)
+  ret void
+}