[MachineOutliner] Fix offset overflow check

The offset overflow check before was incorrect. It would always give the
correct result, but it was comparing the SCALED potential fixed-up offset
against an UNSCALED minimum/maximum. As a result, the outliner was missing a
bunch of frame setup/destroy instructions that ought to have been safe to
outline. This fixes that, and adds an instruction to the .mir test that
failed the old test.
  

llvm-svn: 320090

1 files changed, 6 insertions, 4 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index b88beda4d6b..9e12b1a0e70 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -4833,15 +4833,17 @@ AArch64InstrInfo::getOutliningType(MachineInstr &MI) const {
 
       // Find the minimum/maximum offset for this instruction and check if
       // fixing it up would be in range.
-      int64_t MinOffset, MaxOffset;
-      unsigned DummyScale;
-      getMemOpInfo(MI.getOpcode(), DummyScale, DummyWidth, MinOffset,
+      int64_t MinOffset, MaxOffset; // Unscaled offsets for the instruction.
+      unsigned Scale; // The scale to multiply the offsets by.
+      getMemOpInfo(MI.getOpcode(), Scale, DummyWidth, MinOffset,
                    MaxOffset);
 
       // TODO: We should really test what happens if an instruction overflows.
       // This is tricky to test with IR tests, but when the outliner is moved
       // to a MIR test, it really ought to be checked.
-      if (Offset + 16 < MinOffset || Offset + 16 > MaxOffset)
+
+      Offset += 16; // Update the offset to what it would be if we outlined.
+      if (Offset < MinOffset * Scale || Offset > MaxOffset * Scale)
         return MachineOutlinerInstrType::Illegal;
 
       // It's in range, so we can outline it.