gnu/packages/patches/llvm-9-fix-lpad-miscompilation.patch

   1 From 011fb5bf8b31316472fccb1a19c91912246df9b2 Mon Sep 17 00:00:00 2001
   2 From: Reid Kleckner <rnk@google.com>
   3 Date: Sat, 28 Mar 2020 11:03:14 -0700
   4 Subject: [PATCH] [CodeGen] Fix sinking local values in lpads with phis
   5
   6 There was already a test case for landingpads to handle this case, but I
   7 had forgotten to consider PHI instructions preceding the EH_LABEL in the
   8 landingpad.
   9
  10 PR45261
  11 ---
  12  llvm/lib/CodeGen/SelectionDAG/FastISel.cpp | 17 +++++++++-
  13  llvm/test/CodeGen/X86/sink-local-value.ll  | 36 ++++++++++++++++++++++
  14  2 files changed, 52 insertions(+), 1 deletion(-)
  15
  16 diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
  17 index 5ac3606dc662..2638b1e8a05c 100644
  18 --- llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
  19 +++ llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
  20 @@ -225,6 +225,21 @@ static bool isRegUsedByPhiNodes(unsigned DefReg,
  21    return false;
  22  }
  23
  24 +static bool isTerminatingEHLabel(MachineBasicBlock *MBB, MachineInstr &MI) {
  25 +  // Ignore non-EH labels.
  26 +  if (!MI.isEHLabel())
  27 +    return false;
  28 +
  29 +  // Any EH label outside a landing pad must be for an invoke. Consider it a
  30 +  // terminator.
  31 +  if (!MBB->isEHPad())
  32 +    return true;
  33 +
  34 +  // If this is a landingpad, the first non-phi instruction will be an EH_LABEL.
  35 +  // Don't consider that label to be a terminator.
  36 +  return MI.getIterator() != MBB->getFirstNonPHI();
  37 +}
  38 +
  39  /// Build a map of instruction orders. Return the first terminator and its
  40  /// order. Consider EH_LABEL instructions to be terminators as well, since local
  41  /// values for phis after invokes must be materialized before the call.
  42 @@ -233,7 +248,7 @@ void FastISel::InstOrderMap::initialize(
  43    unsigned Order = 0;
  44    for (MachineInstr &I : *MBB) {
  45      if (!FirstTerminator &&
  46 -        (I.isTerminator() || (I.isEHLabel() && &I != &MBB->front()))) {
  47 +        (I.isTerminator() || isTerminatingEHLabel(MBB, I))) {
  48        FirstTerminator = &I;
  49        FirstTerminatorOrder = Order;
  50      }
  51 diff --git a/llvm/test/CodeGen/X86/sink-local-value.ll b/llvm/test/CodeGen/X86/sink-local-value.ll
  52 index b0e511ac1189..f7d861ac9b6c 100644
  53 --- llvm/test/CodeGen/X86/sink-local-value.ll
  54 +++ llvm/test/CodeGen/X86/sink-local-value.ll
  55 @@ -145,6 +145,42 @@ try.cont:                                         ; preds = %entry, %lpad
  56  ; CHECK:         retl
  57
  58
  59 +define i32 @lpad_phi() personality i32 (...)* @__gxx_personality_v0 {
  60 +entry:
  61 +  store i32 42, i32* @sink_across
  62 +  invoke void @may_throw()
  63 +          to label %try.cont unwind label %lpad
  64 +
  65 +lpad:                                             ; preds = %entry
  66 +  %p = phi i32 [ 11, %entry ]  ; Trivial, but -O0 keeps it
  67 +  %0 = landingpad { i8*, i32 }
  68 +          catch i8* null
  69 +  store i32 %p, i32* @sink_across
  70 +  br label %try.cont
  71 +
  72 +try.cont:                                         ; preds = %entry, %lpad
  73 +  %r.0 = phi i32 [ 13, %entry ], [ 55, %lpad ]
  74 +  ret i32 %r.0
  75 +}
  76 +
  77 +; The constant materialization should be *after* the stores to sink_across, but
  78 +; before any EH_LABEL.
  79 +
  80 +; CHECK-LABEL: lpad_phi:
  81 +; CHECK:         movl    $42, sink_across
  82 +; CHECK:         movl    $13, %{{[a-z]*}}
  83 +; CHECK: .Ltmp{{.*}}:
  84 +; CHECK:         calll   may_throw
  85 +; CHECK: .Ltmp{{.*}}:
  86 +; CHECK:         jmp     .LBB{{.*}}
  87 +; CHECK: .LBB{{.*}}:                                # %lpad
  88 +; CHECK-NEXT: .Ltmp{{.*}}:
  89 +; CHECK:         movl    {{.*}}, sink_across
  90 +; CHECK:         movl    $55, %{{[a-z]*}}
  91 +; CHECK: .LBB{{.*}}:                                # %try.cont
  92 +; CHECK:         retl
  93 +
  94 +
  95  ; Function Attrs: nounwind readnone speculatable
  96  declare void @llvm.dbg.value(metadata, metadata, metadata) #0
  97