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

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-ir

Author: Bryce Kahle (brycekahle)

<details>
<summary>Changes</summary>

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

---
Full diff: https://github.com/llvm/llvm-project/pull/105314.diff


3 Files Affected:

- (modified) llvm/include/llvm/IR/IntrinsicsBPF.td (+3-3) 
- (modified) llvm/test/CodeGen/BPF/sockex2.ll (+1-1) 
- (added) llvm/test/Transforms/DCE/intrinsics-bpf.ll (+33) 


``````````diff
diff --git a/llvm/include/llvm/IR/IntrinsicsBPF.td b/llvm/include/llvm/IR/IntrinsicsBPF.td
index c7ec0916f1d1f..d02eaa6d0dff6 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 4131d9dac31d8..b1264099f64c6 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 0000000000000..135588ba21cbb
--- /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
+}

``````````

</details>


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