Merge pull request #20 from brendangregg/issue18

fix for #18: initializing comm memory

src/ast/codegen_llvm.cpp

@@ -69,6 +69,8 @@ void CodegenLLVM::visit(Builtin &builtin)
   else if (builtin.ident == "comm")
   {
     AllocaInst *buf = b_.CreateAllocaBPF(builtin.type, "comm");
+    // initializing memory needed for older kernels:
+    b_.CreateMemSet(buf, b_.getInt8(0), builtin.type.size, 1);
     b_.CreateGetCurrentComm(buf, builtin.type.size);
     expr_ = buf;
   }

tests/codegen.cpp

@@ -471,6 +471,9 @@ TEST(codegen, builtin_comm)
 R"EXPECTED(; Function Attrs: nounwind
 declare i64 @llvm.bpf.pseudo(i64, i64) #0
 
+; Function Attrs: argmemonly nounwind
+declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i32, i1) #1
+
 ; Function Attrs: argmemonly nounwind
 declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
 
@@ -480,6 +483,7 @@ entry:
   %comm = alloca [64 x i8], align 1
   %1 = getelementptr inbounds [64 x i8], [64 x i8]* %comm, i64 0, i64 0
   call void @llvm.lifetime.start.p0i8(i64 -1, i8* nonnull %1)
+  call void @llvm.memset.p0i8.i64(i8* nonnull %1, i8 0, i64 64, i32 1, i1 false)
   %get_comm = call i64 inttoptr (i64 16 to i64 (i8*, i64)*)([64 x i8]* nonnull %comm, i64 64)
   %2 = bitcast i64* %"@x_key" to i8*
   call void @llvm.lifetime.start.p0i8(i64 -1, i8* nonnull %2)
@@ -1064,6 +1068,9 @@ TEST(codegen, variable)
 R"EXPECTED(; Function Attrs: nounwind
 declare i64 @llvm.bpf.pseudo(i64, i64) #0
 
+; Function Attrs: argmemonly nounwind
+declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i32, i1) #1
+
 ; Function Attrs: argmemonly nounwind
 declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #1
 
@@ -1074,6 +1081,7 @@ entry:
   %comm = alloca [64 x i8], align 1
   %1 = getelementptr inbounds [64 x i8], [64 x i8]* %comm, i64 0, i64 0
   call void @llvm.lifetime.start.p0i8(i64 -1, i8* nonnull %1)
+  call void @llvm.memset.p0i8.i64(i8* nonnull %1, i8 0, i64 64, i32 1, i1 false)
   %get_comm = call i64 inttoptr (i64 16 to i64 (i8*, i64)*)([64 x i8]* nonnull %comm, i64 64)
   %2 = bitcast i64* %"@x_key" to i8*
   call void @llvm.lifetime.start.p0i8(i64 -1, i8* nonnull %2)