[CodeView] Fix off-by-one error in def range gap emission

Also fixes a much worse bug where we emitted the wrong gap size for the
def range uncovered by the test for this issue.

Fixes PR31726.

llvm-svn: 292949

2 files changed, 30 insertions, 6 deletions

diff --git a/llvm/lib/MC/MCCodeView.cpp b/llvm/lib/MC/MCCodeView.cpp
index 3773542cf8a..99a5c11a498 100644
--- a/llvm/lib/MC/MCCodeView.cpp
+++ b/llvm/lib/MC/MCCodeView.cpp
@@ -509,17 +509,17 @@ void CodeViewContext::encodeDefRange(MCAsmLayout &Layout,
       // are artificially constructing.
       size_t RecordSize = FixedSizePortion.size() +
                           sizeof(LocalVariableAddrRange) + 4 * NumGaps;
-      // Write out the recrod size.
-      support::endian::Writer<support::little>(OS).write<uint16_t>(RecordSize);
+      // Write out the record size.
+      LEWriter.write<uint16_t>(RecordSize);
       // Write out the fixed size prefix.
       OS << FixedSizePortion;
       // Make space for a fixup that will eventually have a section relative
       // relocation pointing at the offset where the variable becomes live.
       Fixups.push_back(MCFixup::create(Contents.size(), BE, FK_SecRel_4));
-      Contents.resize(Contents.size() + 4); // Fixup for code start.
+      LEWriter.write<uint32_t>(0); // Fixup for code start.
       // Make space for a fixup that will record the section index for the code.
       Fixups.push_back(MCFixup::create(Contents.size(), BE, FK_SecRel_2));
-      Contents.resize(Contents.size() + 2); // Fixup for section index.
+      LEWriter.write<uint16_t>(0); // Fixup for section index.
       // Write down the range's extent.
       LEWriter.write<uint16_t>(Chunk);
 
@@ -529,7 +529,7 @@ void CodeViewContext::encodeDefRange(MCAsmLayout &Layout,
     } while (RangeSize > 0);
 
     // Emit the gaps afterwards.
-    assert((NumGaps == 0 || Bias < MaxDefRange) &&
+    assert((NumGaps == 0 || Bias <= MaxDefRange) &&
            "large ranges should not have gaps");
     unsigned GapStartOffset = GapAndRangeSizes[I].second;
     for (++I; I != J; ++I) {
@@ -537,7 +537,7 @@ void CodeViewContext::encodeDefRange(MCAsmLayout &Layout,
       assert(I < GapAndRangeSizes.size());
       std::tie(GapSize, RangeSize) = GapAndRangeSizes[I];
       LEWriter.write<uint16_t>(GapStartOffset);
-      LEWriter.write<uint16_t>(RangeSize);
+      LEWriter.write<uint16_t>(GapSize);
       GapStartOffset += GapSize + RangeSize;
     }
   }
diff --git a/llvm/test/MC/COFF/cv-def-range-gap.s b/llvm/test/MC/COFF/cv-def-range-gap.s
index 243e777d92e..9c153181996 100644
--- a/llvm/test/MC/COFF/cv-def-range-gap.s
+++ b/llvm/test/MC/COFF/cv-def-range-gap.s
@@ -38,6 +38,19 @@
 # CHECK-NEXT:        Range: 0x1
 # CHECK-NEXT:      }
 # CHECK-NEXT:    }
+# CHECK-NEXT:    DefRangeRegister {
+# CHECK-NEXT:      Register: 23
+# CHECK-NEXT:      MayHaveNoName: 0
+# CHECK-NEXT:      LocalVariableAddrRange {
+# CHECK-NEXT:        OffsetStart: .text+0x2001C
+# CHECK-NEXT:        ISectStart: 0x0
+# CHECK-NEXT:        Range: 0xF000
+# CHECK-NEXT:      }
+# CHECK-NEXT:      LocalVariableAddrGap [
+# CHECK-NEXT:        GapStartOffset: 0x1
+# CHECK-NEXT:        Range: 0xEFFE
+# CHECK-NEXT:      ]
+# CHECK-NEXT:    }
 
 	.text
 f:                                      # @f
@@ -62,6 +75,16 @@ f:                                      # @f
 .Lbegin3:
 	nop
 .Lend3:
+
+	# Create a range that is exactly 0xF000 bytes long with a gap in the
+	# middle.
+.Lbegin4:
+	nop
+.Lend4:
+	.fill 0xeffe, 1, 0x90
+.Lbegin5:
+	nop
+.Lend5:
 	ret
 .Lfunc_end0:
 
@@ -94,6 +117,7 @@ f:                                      # @f
 	.asciz	"p"
 .Ltmp19:
 	.cv_def_range	 .Lbegin0 .Lend0 .Lbegin1 .Lend1 .Lbegin2 .Lend2 .Lbegin3 .Lend3, "A\021\027\000\000\000"
+	.cv_def_range	 .Lbegin4 .Lend4 .Lbegin5 .Lend5, "A\021\027\000\000\000"
 	.short	2                       # Record length
 	.short	4431                    # Record kind: S_PROC_ID_END
 .Ltmp15: