From: Jiong Wang <jiwang@tilera.com>
Date: Thu, 28 Feb 2019 19:21:28 +0000 (+0000)
Subject: bpf: enable sub-register code-gen for XADD
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=b17832255a6eaf95677f322fd834a8450bc20cff;p=llvm

bpf: enable sub-register code-gen for XADD

Support sub-register code-gen for XADD is like supporting any other Load
and Store patterns.

No new instruction is introduced.

  lock *(u32 *)(r1 + 0) += w2

has exactly the same underlying insn as:

  lock *(u32 *)(r1 + 0) += r2

BPF_W width modifier has guaranteed they behave the same at runtime. This
patch merely teaches BPF back-end that BPF_W width modifier could work
GPR32 register class and that's all needed for sub-register code-gen
support for XADD.

test/CodeGen/BPF/xadd.ll updated to include sub-register code-gen tests.

A new testcase test/CodeGen/BPF/xadd_legal.ll is added to make sure the
legal case could pass on all code-gen modes. It could also test dead Def
check on GPR32. If there is no proper handling like what has been done
inside BPFMIChecking.cpp:hasLivingDefs, then this testcase will fail.

Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355126 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/BPF/BPFInstrInfo.td b/lib/Target/BPF/BPFInstrInfo.td
index 36724b81fc6..c44702a78ec 100644
--- a/lib/Target/BPF/BPFInstrInfo.td
+++ b/lib/Target/BPF/BPFInstrInfo.td
@@ -614,11 +614,31 @@ class XADD<BPFWidthModifer SizeOp, string OpcodeStr, PatFrag OpNode>
   let BPFClass = BPF_STX;
 }
 
+class XADD32<BPFWidthModifer SizeOp, string OpcodeStr, PatFrag OpNode>
+    : TYPE_LD_ST<BPF_XADD.Value, SizeOp.Value,
+                 (outs GPR32:$dst),
+                 (ins MEMri:$addr, GPR32:$val),
+                 "lock *("#OpcodeStr#" *)($addr) += $val",
+                 [(set GPR32:$dst, (OpNode ADDRri:$addr, GPR32:$val))]> {
+  bits<4> dst;
+  bits<20> addr;
+
+  let Inst{51-48} = addr{19-16}; // base reg
+  let Inst{55-52} = dst;
+  let Inst{47-32} = addr{15-0}; // offset
+  let BPFClass = BPF_STX;
+}
+
 let Constraints = "$dst = $val" in {
-def XADD32 : XADD<BPF_W, "u32", atomic_load_add_32>;
-def XADD64 : XADD<BPF_DW, "u64", atomic_load_add_64>;
-// undefined def XADD16 : XADD<1, "xadd16", atomic_load_add_16>;
-// undefined def XADD8  : XADD<2, "xadd8", atomic_load_add_8>;
+  let Predicates = [BPFNoALU32] in {
+    def XADDW : XADD<BPF_W, "u32", atomic_load_add_32>;
+  }
+
+  let Predicates = [BPFHasALU32], DecoderNamespace = "BPFALU32" in {
+    def XADDW32 : XADD32<BPF_W, "u32", atomic_load_add_32>;
+  }
+
+  def XADDD : XADD<BPF_DW, "u64", atomic_load_add_64>;
 }
 
 // bswap16, bswap32, bswap64
diff --git a/lib/Target/BPF/BPFMIChecking.cpp b/lib/Target/BPF/BPFMIChecking.cpp
index 514af76b845..4c46289656b 100644
--- a/lib/Target/BPF/BPFMIChecking.cpp
+++ b/lib/Target/BPF/BPFMIChecking.cpp
@@ -155,7 +155,9 @@ static bool hasLiveDefs(const MachineInstr &MI, const TargetRegisterInfo *TRI) {
 void BPFMIPreEmitChecking::checkingIllegalXADD(void) {
   for (MachineBasicBlock &MBB : *MF) {
     for (MachineInstr &MI : MBB) {
-      if (MI.getOpcode() != BPF::XADD32 && MI.getOpcode() != BPF::XADD64)
+      if (MI.getOpcode() != BPF::XADDW &&
+          MI.getOpcode() != BPF::XADDD &&
+          MI.getOpcode() != BPF::XADDW32)
         continue;
 
       LLVM_DEBUG(MI.dump());
diff --git a/test/CodeGen/BPF/xadd.ll b/test/CodeGen/BPF/xadd.ll
index c5f2620179e..49f0c10c318 100644
--- a/test/CodeGen/BPF/xadd.ll
+++ b/test/CodeGen/BPF/xadd.ll
@@ -1,5 +1,7 @@
 ; RUN: not llc -march=bpfel < %s 2>&1 | FileCheck %s
 ; RUN: not llc -march=bpfeb < %s 2>&1 | FileCheck %s
+; RUN: not llc -march=bpfel -mattr=+alu32 < %s 2>&1 | FileCheck %s
+; RUN: not llc -march=bpfeb -mattr=+alu32 < %s 2>&1 | FileCheck %s
 
 ; This file is generated with the source command and source
 ; $ clang -target bpf -O2 -g -S -emit-llvm t.c
diff --git a/test/CodeGen/BPF/xadd_legal.ll b/test/CodeGen/BPF/xadd_legal.ll
new file mode 100644
index 00000000000..0d30084af8b
--- /dev/null
+++ b/test/CodeGen/BPF/xadd_legal.ll
@@ -0,0 +1,26 @@
+; RUN: llc -march=bpfel < %s 2>&1 | FileCheck --check-prefix=CHECK-64 %s
+; RUN: llc -march=bpfeb < %s 2>&1 | FileCheck --check-prefix=CHECK-64 %s
+; RUN: llc -march=bpfel -mattr=+alu32 < %s 2>&1 | FileCheck --check-prefix=CHECK-32 %s
+; RUN: llc -march=bpfeb -mattr=+alu32 < %s 2>&1 | FileCheck --check-prefix=CHECK-32 %s
+
+; This file is generated with the source command and source
+; $ clang -target bpf -O2 -S -emit-llvm t.c
+; $ cat t.c
+; int test(int *ptr, unsigned long long a) {
+;    __sync_fetch_and_add(ptr, a);
+;    return *ptr;
+; }
+;
+; NOTE: passing unsigned long long as the second operand of __sync_fetch_and_add
+; could effectively create sub-register reference coming from indexing a full
+; register which could then exerceise hasLivingDefs inside BPFMIChecker.cpp.
+
+define dso_local i32 @test(i32* nocapture %ptr, i64 %a) {
+entry:
+  %conv = trunc i64 %a to i32
+  %0 = atomicrmw add i32* %ptr, i32 %conv seq_cst
+; CHECK-64: lock *(u32 *)(r1 + 0) += r2
+; CHECK-32: lock *(u32 *)(r1 + 0) += w2
+  %1 = load i32, i32* %ptr, align 4
+  ret i32 %1
+}