bpf: fix incorrect SELECT_CC lowering

Commit 37962a331c77 ("bpf: Improve expanding logic in LowerSELECT_CC")
intended to improve code quality for certain jmp conditions. The
commit, however, has a couple of issues:
  (1). In code, just swap is not enough, ConditionalCode CC
       should also be swapped, otherwise incorrect code will
       be generated.
  (2). The ConditionalCode swap should be subject to
       getHasJmpExt(). If getHasJmpExt() is False, certain
       conditional codes will not be supported and swap
       may generate incorrect code.

The original goal for this patch is to optimize jmp operations
which does not have JmpExt turned on. If JmpExt is on,
better code could be generated. For example, the test
select_ri.ll is introduced to demonstrate the optimization.
The same result can be achieved with -mcpu=v2 flag.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 329043

4 files changed, 3 insertions, 9 deletions

diff --git a/llvm/lib/Target/BPF/BPFISelLowering.cpp b/llvm/lib/Target/BPF/BPFISelLowering.cpp
index e02cdf579d2..e81c2f5f832 100644
--- a/llvm/lib/Target/BPF/BPFISelLowering.cpp
+++ b/llvm/lib/Target/BPF/BPFISelLowering.cpp
@@ -502,13 +502,7 @@ SDValue BPFTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
     NegateCC(LHS, RHS, CC);
 
   SDValue TargetCC = DAG.getConstant(CC, DL, LHS.getValueType());
-
   SDVTList VTs = DAG.getVTList(Op.getValueType(), MVT::Glue);
-
-  // The constant is expected at RHS in Select_Ri pattern.
-  if (isa<ConstantSDNode>(LHS.getNode()))
-    std::swap(LHS, RHS);
-
   SDValue Ops[] = {LHS, RHS, TargetCC, TrueV, FalseV};
 
   return DAG.getNode(BPFISD::SELECT_CC, DL, VTs, Ops);
diff --git a/llvm/test/CodeGen/BPF/32-bit-subreg-peephole.ll b/llvm/test/CodeGen/BPF/32-bit-subreg-peephole.ll
index ed5268458f8..cf68ec56ca3 100644
--- a/llvm/test/CodeGen/BPF/32-bit-subreg-peephole.ll
+++ b/llvm/test/CodeGen/BPF/32-bit-subreg-peephole.ll
@@ -1,4 +1,4 @@
-; RUN: llc -O2 -march=bpfel -mattr=+alu32 < %s | FileCheck %s
+; RUN: llc -O2 -march=bpfel -mcpu=v2 -mattr=+alu32 < %s | FileCheck %s
 ;
 ; long long select_u(unsigned a, unsigned b, long long c, long long d)
 ; {
diff --git a/llvm/test/CodeGen/BPF/cmp.ll b/llvm/test/CodeGen/BPF/cmp.ll
index d86f1903ffe..44f00ff02c4 100644
--- a/llvm/test/CodeGen/BPF/cmp.ll
+++ b/llvm/test/CodeGen/BPF/cmp.ll
@@ -97,7 +97,7 @@ define zeroext i8 @minu(i8 zeroext %a, i8 zeroext %b) #0 {
   %a.b = select i1 %1, i8 %a, i8 %b
   ret i8 %a.b
 ; CHECK-LABEL:minu:
-; CHECK: if r{{[0-9]+}} {{<|>}} 100
+; CHECK: if r{{[0-9]+}} {{<|>}} r{{[0-9]+}}
 }
 
 ; Function Attrs: nounwind readnone uwtable
diff --git a/llvm/test/CodeGen/BPF/select_ri.ll b/llvm/test/CodeGen/BPF/select_ri.ll
index dbd21113d7f..61e852d74b0 100644
--- a/llvm/test/CodeGen/BPF/select_ri.ll
+++ b/llvm/test/CodeGen/BPF/select_ri.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -march=bpf -verify-machineinstrs | FileCheck %s
+; RUN: llc < %s -march=bpf -mcpu=v2 -verify-machineinstrs | FileCheck %s
 ;
 ; Source file:
 ; int b, c;