[llvm-dev] 5.0.1-rc2 has been tagged

[Y Song via llvm-dev]

Hi, Tom,

I have a BPF backend bug which is pretty noxious which is introduced
in 5.0 and fixed in 6.0 trunk.
The detailed of the backport commit is at the end of this email, which
is slightly different from
6.0 fix to adjust the asm output format. Is there a way for this bug
fix into 5.0.1 release and if yes,
what is the process?

I have applied the commit below to latest release_50 branch in my
local repo and run through all BPF tests
and they are fine.

Thanks!

Yonghong

===== Commit to backport Details =====
commit a115edb82180f0c94d692c4abfd631984ada156b
Author: Yonghong Song <yhs at fb.com>
Date:   Mon Oct 16 04:14:53 2017 +0000

    bpf: fix bug on silently truncating 64-bit immediate

    We came across an llvm bug when compiling some testcases that 64-bit
    immediates are silently truncated into 32-bit and then packed into
    BPF_JMP | BPF_K encoding.  This caused comparison with wrong value.

    This bug looks to be introduced by r308080 (llvm 5.0). The
Select_Ri pattern is
    supposed to be lowered into J*_Ri while the latter only support 32-bit
    immediate encoding, therefore Select_Ri should have similar immediate
    predicate check as what J*_Ri are doing.

    The bug is fixed by
    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315889
91177308-0d34-0410-b5e6-96231b3b80d8
    in llvm 6.0.

    This patch is largely the same as the fix in llvm 6.0 except
    one minor adjustment ("; CHECK:  r{{[0-9]+}} = 8589934591 ll" in
the original commit
    to "; CHECK:  r{{[0-9]+}} = 8589934591ll" in this patch) for the test case.

    Reported-by: John Fastabend <john.fastabend at gmail.com>
    Reported-by: Jakub Kicinski <jakub.kicinski at netronome.com>
    Signed-off-by: Jiong Wang <jiong.wang at netronome.com>
    Reviewed-by: Yonghong Song <yhs at fb.com>

diff --git a/lib/Target/BPF/BPFISelLowering.cpp
b/lib/Target/BPF/BPFISelLowering.cpp
index 81b0aa7..5740b49 100644
--- a/lib/Target/BPF/BPFISelLowering.cpp
+++ b/lib/Target/BPF/BPFISelLowering.cpp
@@ -578,11 +578,15 @@
BPFTargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
         .addReg(LHS)
         .addReg(MI.getOperand(2).getReg())
         .addMBB(Copy1MBB);
-  else
+  else {
+    int64_t imm32 = MI.getOperand(2).getImm();
+    // sanity check before we build J*_ri instruction.
+    assert (isInt<32>(imm32));
     BuildMI(BB, DL, TII.get(NewCC))
         .addReg(LHS)
-        .addImm(MI.getOperand(2).getImm())
+        .addImm(imm32)
         .addMBB(Copy1MBB);
+  }

   // Copy0MBB:
   //  %FalseValue = ...
diff --git a/lib/Target/BPF/BPFInstrInfo.td b/lib/Target/BPF/BPFInstrInfo.td
index f683578..56f0f9c 100644
--- a/lib/Target/BPF/BPFInstrInfo.td
+++ b/lib/Target/BPF/BPFInstrInfo.td
@@ -464,7 +464,7 @@ let usesCustomInserter = 1 in {
                       (ins GPR:$lhs, i64imm:$rhs, i64imm:$imm,
GPR:$src, GPR:$src2),
                       "# Select PSEUDO $dst = $lhs $imm $rhs ? $src : $src2",
                       [(set i64:$dst,
-                       (BPFselectcc i64:$lhs, (i64 imm:$rhs), (i64
imm:$imm), i64:$src, i64:$src2))]>;
+                       (BPFselectcc i64:$lhs, (i64immSExt32:$rhs),
(i64 imm:$imm), i64:$src, i64:$src2))]>;
 }

 // load 64-bit global addr into register
diff --git a/test/CodeGen/BPF/select_ri.ll b/test/CodeGen/BPF/select_ri.ll
index c4ac376..3610d40 100644
--- a/test/CodeGen/BPF/select_ri.ll
+++ b/test/CodeGen/BPF/select_ri.ll
@@ -25,3 +25,38 @@ entry:
 }

 attributes #0 = { norecurse nounwind readonly }
+
+; test immediate out of 32-bit range
+; Source file:
+
+; unsigned long long
+; load_word(void *buf, unsigned long long off)
+; asm("llvm.bpf.load.word");
+;
+; int
+; foo(void *buf)
+; {
+;  unsigned long long sum = 0;
+;
+;  sum += load_word(buf, 100);
+;  sum += load_word(buf, 104);
+;
+;  if (sum != 0x1ffffffffULL)
+;    return ~0U;
+;
+;  return 0;
+;}
+
+; Function Attrs: nounwind readonly
+define i32 @foo(i8*) local_unnamed_addr #0 {
+  %2 = tail call i64 @llvm.bpf.load.word(i8* %0, i64 100)
+  %3 = tail call i64 @llvm.bpf.load.word(i8* %0, i64 104)
+  %4 = add i64 %3, %2
+  %5 = icmp ne i64 %4, 8589934591
+; CHECK:  r{{[0-9]+}} = 8589934591ll
+  %6 = sext i1 %5 to i32
+  ret i32 %6
+}
+
+; Function Attrs: nounwind readonly
+declare i64 @llvm.bpf.load.word(i8*, i64) #1

On Wed, Nov 29, 2017 at 4:19 PM, Tom Stellard via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> I've tagged the 5.0.1-rc2 release, go ahead and start testing and report
> your results.
>
> -Tom
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
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