[llvm] r325267 - bpf: fix a bug in dag2dag optimization for loads from readonly section

[Yonghong Song via llvm-commits]

Author: yhs
Date: Thu Feb 15 09:06:45 2018
New Revision: 325267

URL: http://llvm.org/viewvc/llvm-project?rev=325267&view=rev
Log:
bpf: fix a bug in dag2dag optimization for loads from readonly section

The reference '&' is missing in the function parameter. If there are
back-to-back optimizations in terms of dag node list like below:
  t29: i64,ch = load<LD4[bitcast (%struct.test_t* @test.t to i8*)+12](dereferenceable), zext from i32> t3, t43, undef:i64
  t34: i64,ch = load<LD4[bitcast (%struct.test_t* @test.t to i8*)](dereferenceable), zext from i32> t3, t41, undef:i64
The bug will trigger a segfault for the added test case remove_truncate_5.ll:
  LLVMSymbolizer: error reading file: No such file or directory
  #0 0x000000000241c4d9 (llc+0x241c4d9)
  #1 0x000000000241c56a (llc+0x241c56a)
  #2 0x000000000241aa50 (llc+0x241aa50)
  ...
  #22 0x0000000000fd5edf (llc+0xfd5edf)
  #23 0x00007f0fe03bec05 __libc_start_main (/lib64/libc.so.6+0x21c05)
  #24 0x0000000000fd3e69 (llc+0xfd3e69)
  ...
  Segmentation fault

Signed-off-by: Yonghong Song <yhs at fb.com>

Added:
    llvm/trunk/test/CodeGen/BPF/remove_truncate_5.ll
Modified:
    llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp

Modified: llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp?rev=325267&r1=325266&r2=325267&view=diff
==============================================================================
--- llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp (original)
+++ llvm/trunk/lib/Target/BPF/BPFISelDAGToDAG.cpp Thu Feb 15 09:06:45 2018
@@ -65,9 +65,9 @@ private:
   bool SelectFIAddr(SDValue Addr, SDValue &Base, SDValue &Offset);
 
   // Node preprocessing cases
-  void PreprocessLoad(SDNode *Node, SelectionDAG::allnodes_iterator I);
+  void PreprocessLoad(SDNode *Node, SelectionDAG::allnodes_iterator &I);
   void PreprocessCopyToReg(SDNode *Node);
-  void PreprocessTrunc(SDNode *Node, SelectionDAG::allnodes_iterator I);
+  void PreprocessTrunc(SDNode *Node, SelectionDAG::allnodes_iterator &I);
 
   // Find constants from a constant structure
   typedef std::vector<unsigned char> val_vec_type;
@@ -238,7 +238,7 @@ void BPFDAGToDAGISel::Select(SDNode *Nod
 }
 
 void BPFDAGToDAGISel::PreprocessLoad(SDNode *Node,
-                                     SelectionDAG::allnodes_iterator I) {
+                                     SelectionDAG::allnodes_iterator &I) {
   union {
     uint8_t c[8];
     uint16_t s;
@@ -511,7 +511,7 @@ void BPFDAGToDAGISel::PreprocessCopyToRe
 }
 
 void BPFDAGToDAGISel::PreprocessTrunc(SDNode *Node,
-                                      SelectionDAG::allnodes_iterator I) {
+                                      SelectionDAG::allnodes_iterator &I) {
   ConstantSDNode *MaskN = dyn_cast<ConstantSDNode>(Node->getOperand(1));
   if (!MaskN)
     return;

Added: llvm/trunk/test/CodeGen/BPF/remove_truncate_5.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/BPF/remove_truncate_5.ll?rev=325267&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/BPF/remove_truncate_5.ll (added)
+++ llvm/trunk/test/CodeGen/BPF/remove_truncate_5.ll Thu Feb 15 09:06:45 2018
@@ -0,0 +1,53 @@
+; RUN: llc < %s -march=bpfel | FileCheck -check-prefixes=CHECK %s
+
+; Source code:
+; struct test_t {
+;       int a;
+;       char b;
+;       int c;
+;       char d;
+; };
+; void foo(void *);
+; void test() {
+;       struct test_t t = {.a = 5};
+;       foo(&t);
+; }
+
+%struct.test_t = type { i32, i8, i32, i8 }
+
+ at test.t = private unnamed_addr constant %struct.test_t { i32 5, i8 0, i32 0, i8 0 }, align 4
+
+; Function Attrs: nounwind
+define dso_local void @test() local_unnamed_addr #0 {
+; CHECK-LABEL: test:
+  %1 = alloca %struct.test_t, align 4
+  %2 = bitcast %struct.test_t* %1 to i8*
+  call void @llvm.lifetime.start.p0i8(i64 16, i8* nonnull %2) #3
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* nonnull align 4 %2, i8* align 4 bitcast (%struct.test_t* @test.t to i8*), i64 16, i1 false)
+; CHECK: r1 = 0
+; CHECK: r1 <<= 32
+; CHECK: r2 = r1
+; CHECK: r2 |= 0
+; CHECK: *(u64 *)(r10 - 8) = r2
+; CHECK: r1 |= 5
+; CHECK: *(u64 *)(r10 - 16) = r1
+  call void @foo(i8* nonnull %2) #3
+; CHECK: call foo
+  call void @llvm.lifetime.end.p0i8(i64 16, i8* nonnull %2) #3
+  ret void
+}
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i1) #1
+
+declare dso_local void @foo(i8*) local_unnamed_addr
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { argmemonly nounwind }
+attributes #3 = { nounwind }