DWARF: Fix handling of the end of control flow instructions (#3288)

Previously when we processed a block for example, we'd do this:

;; start is here
(block (result type)
;; end is here
  .. contents ..
)
;; end delimiter is here

Not how this represents the block's start and end as the "header", and
uses an extra delimiter to mark the end.

I think this is wrong, and was an attempt to handle some offsets from
LLVM that otherwise made no sense, ones at the end of the "header".
But it turns out that this makes us completely incorrect on some things
where there is a low/high pc pair, and we need to understand that the
end of a block is at the end opcode at the very end, and not the end of
the header. This PR changes us to do that, i.e.

;; start is here
(block (result type)
  .. contents ..
)
;; end is here

This fixes a testcase already in the test suite,

test/passes/fib_nonzero-low-pc_dwarf.bin.txt

where you can see that lexical block now has a valid value for the end, and
not a 0 (the proper scope extends all the way to the end of the big block in
that function, and is now the same in the DWARF before and after we
process it). test/passes/fannkuch3_dwarf.bin.txt is also improved by
this.

To implement this, this removes the BinaryLocations::End delimeter. After
this we just need one type of delimiter actually, but I didn't refactor that any
more to keep this PR small (see TODO).

This removes an assertion in writeDebugLocationEnd() that is no longer
valid: the assert ensures that we wrote an end only if there was a 0 for
the end, but for a control flow structure, we write the end of the "header"
automatically like for any expression, and then overwrite it later when we
finish writing the children and the end marker. We could in theory special-case
control flow structures to avoid the first write, but it would add more complexity.

This uncovered what appears to be a possible bug in our debug_line
handling, see test/passes/fannkuch3_manyopts_dwarf.bin.txt. That needs
to be looked into more, but I suspect that was invalid info from when we
looked at the end of the "header" of control flow structures. Note that there
was one definite bug uncovered here, fixed by the extra

} else if (locationUpdater.hasOldExprEnd(oldAddr)) {

that is added here, which was definitely a bug.

7 files changed, 181 insertions, 204 deletions

diff --git a/src/wasm.h b/src/wasm.h
index 04e2faeb3..295088780 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -1413,10 +1413,10 @@ struct BinaryLocations {
   // control flow, have, like 'end' for loop and block. We keep these in a
   // separate map because they are rare and we optimize for the storage space
   // for the common type of instruction which just needs a Span. We implement
-  // this as a simple struct with two elements (as two extra elements is the
-  // maximum currently needed; due to 'catch' and 'end' for try-catch). The
-  // second value may be 0, indicating it is not used.
-  struct DelimiterLocations : public std::array<BinaryLocation, 2> {
+  // this as a simple array with one element at the moment (more elements may
+  // be necessary in the future).
+  // TODO: If we are sure we won't need more, make this a single value?
+  struct DelimiterLocations : public std::array<BinaryLocation, 1> {
     DelimiterLocations() {
       // Ensure zero-initialization.
       for (auto& item : *this) {
@@ -1425,14 +1425,7 @@ struct BinaryLocations {
     }
   };
 
-  enum DelimiterId {
-    // All control flow structures have an end, so use index 0 for that.
-    End = 0,
-    // Use index 1 for all other current things.
-    Else = 1,
-    Catch = 1,
-    Invalid = -1
-  };
+  enum DelimiterId { Else = 0, Catch = 0, Invalid = -1 };
   std::unordered_map<Expression*, DelimiterLocations> delimiters;
 
   // DWARF debug info can refer to multiple interesting positions in a function.
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 5c25fd0d2..0c56af8e0 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -865,7 +865,6 @@ void WasmBinaryWriter::writeDebugLocation(Expression* curr, Function* func) {
 void WasmBinaryWriter::writeDebugLocationEnd(Expression* curr, Function* func) {
   if (func && !func->expressionLocations.empty()) {
     auto& span = binaryLocations.expressions.at(curr);
-    assert(span.end == 0);
     span.end = o.size();
   }
 }
@@ -2580,7 +2579,12 @@ BinaryConsts::ASTNodes WasmBinaryBuilder::readExpression(Expression*& curr) {
       break;
     case BinaryConsts::End:
       curr = nullptr;
-      continueControlFlow(BinaryLocations::End, startPos);
+      // Pop the current control flow structure off the stack. If there is none
+      // then this is the "end" of the function itself, which also emits an
+      // "end" byte.
+      if (!controlFlowStack.empty()) {
+        controlFlowStack.pop_back();
+      }
       break;
     case BinaryConsts::Else:
       curr = nullptr;
@@ -2808,22 +2812,12 @@ void WasmBinaryBuilder::startControlFlow(Expression* curr) {
 void WasmBinaryBuilder::continueControlFlow(BinaryLocations::DelimiterId id,
                                             BinaryLocation pos) {
   if (DWARF && currFunction) {
-    if (controlFlowStack.empty()) {
-      // We reached the end of the function, which is also marked with an
-      // "end", like a control flow structure.
-      assert(id == BinaryLocations::End);
-      assert(pos + 1 == endOfFunction);
-      return;
-    }
     assert(!controlFlowStack.empty());
     auto currControlFlow = controlFlowStack.back();
     // We are called after parsing the byte, so we need to subtract one to
     // get its position.
     currFunction->delimiterLocations[currControlFlow][id] =
       pos - codeSectionLocation;
-    if (id == BinaryLocations::End) {
-      controlFlowStack.pop_back();
-    }
   }
 }
 
diff --git a/src/wasm/wasm-debug.cpp b/src/wasm/wasm-debug.cpp
index 0f37374b5..448bcaaa9 100644
--- a/src/wasm/wasm-debug.cpp
+++ b/src/wasm/wasm-debug.cpp
@@ -680,6 +680,8 @@ static void updateDebugLines(llvm::DWARFYAML::Data& data,
           newAddr = locationUpdater.getNewFuncStart(oldAddr);
         } else if (locationUpdater.hasOldDelimiter(oldAddr)) {
           newAddr = locationUpdater.getNewDelimiter(oldAddr);
+        } else if (locationUpdater.hasOldExprEnd(oldAddr)) {
+          newAddr = locationUpdater.getNewExprEnd(oldAddr);
         }
         if (newAddr && state.needToEmit()) {
           // LLVM sometimes emits the same address more than once. We should
diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index 2ec156eea..1d290f53c 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -1880,10 +1880,10 @@ void BinaryInstWriter::visitArrayLen(ArrayLen* curr) {
 void BinaryInstWriter::emitScopeEnd(Expression* curr) {
   assert(!breakStack.empty());
   breakStack.pop_back();
+  o << int8_t(BinaryConsts::End);
   if (func && !sourceMap) {
-    parent.writeExtraDebugLocation(curr, func, BinaryLocations::End);
+    parent.writeDebugLocationEnd(curr, func);
   }
-  o << int8_t(BinaryConsts::End);
 }
 
 void BinaryInstWriter::emitFunctionEnd() { o << int8_t(BinaryConsts::End); }
diff --git a/test/passes/fannkuch3_dwarf.bin.txt b/test/passes/fannkuch3_dwarf.bin.txt
index 84be99be5..ae8a30e65 100644
--- a/test/passes/fannkuch3_dwarf.bin.txt
+++ b/test/passes/fannkuch3_dwarf.bin.txt
@@ -2851,7 +2851,7 @@ Abbrev table for offset: 0x00000000
 0x00000278:     DW_TAG_inlined_subroutine [24] *
                   DW_AT_abstract_origin [DW_FORM_ref4]	(cu + 0x01a8 => {0x000001a8} "_ZL8fannkuchi")
                   DW_AT_low_pc [DW_FORM_addr]	(0x00000000000003ec)
-                  DW_AT_high_pc [DW_FORM_data4]	(0x0000026c)
+                  DW_AT_high_pc [DW_FORM_data4]	(0x0000029e)
                   DW_AT_call_file [DW_FORM_data1]	("/usr/local/google/home/azakai/Dev/emscripten/tests/fannkuch.cpp")
                   DW_AT_call_line [DW_FORM_data1]	(159)
                   DW_AT_call_column [DW_FORM_data1]	(0x29)
diff --git a/test/passes/fannkuch3_manyopts_dwarf.bin.txt b/test/passes/fannkuch3_manyopts_dwarf.bin.txt
index 36c9db37b..20b59c325 100644
--- a/test/passes/fannkuch3_manyopts_dwarf.bin.txt
+++ b/test/passes/fannkuch3_manyopts_dwarf.bin.txt
@@ -2303,7 +2303,7 @@ Contains section .debug_info (851 bytes)
 Contains section .debug_loc (1073 bytes)
 Contains section .debug_ranges (88 bytes)
 Contains section .debug_abbrev (333 bytes)
-Contains section .debug_line (2702 bytes)
+Contains section .debug_line (2682 bytes)
 Contains section .debug_str (434 bytes)
 
 .debug_abbrev contents:
@@ -3119,7 +3119,7 @@ Abbrev table for offset: 0x00000000
 .debug_line contents:
 debug_line[0x00000000]
 Line table prologue:
-    total_length: 0x00000a8a
+    total_length: 0x00000a76
          version: 4
  prologue_length: 0x000000dd
  min_inst_length: 1
@@ -4364,299 +4364,287 @@ file_names[  4]:
             0x0000000000000547    122     14      1   0             0 
 
 
-0x000008a5: 00 DW_LNE_set_address (0x000000000000054c)
-0x000008ac: 03 DW_LNS_advance_line (130)
-0x000008ae: 06 DW_LNS_negate_stmt
-0x000008af: 01 DW_LNS_copy
-            0x000000000000054c    130     14      1   0             0  is_stmt
-
-
-0x000008b0: 00 DW_LNE_set_address (0x000000000000054d)
-0x000008b7: 03 DW_LNS_advance_line (110)
-0x000008b9: 05 DW_LNS_set_column (11)
-0x000008bb: 01 DW_LNS_copy
+0x000008a5: 00 DW_LNE_set_address (0x000000000000054d)
+0x000008ac: 03 DW_LNS_advance_line (110)
+0x000008ae: 05 DW_LNS_set_column (11)
+0x000008b0: 06 DW_LNS_negate_stmt
+0x000008b1: 01 DW_LNS_copy
             0x000000000000054d    110     11      1   0             0  is_stmt
 
 
-0x000008bc: 00 DW_LNE_set_address (0x0000000000000559)
-0x000008c3: 03 DW_LNS_advance_line (113)
-0x000008c5: 05 DW_LNS_set_column (10)
-0x000008c7: 01 DW_LNS_copy
+0x000008b2: 00 DW_LNE_set_address (0x0000000000000559)
+0x000008b9: 03 DW_LNS_advance_line (113)
+0x000008bb: 05 DW_LNS_set_column (10)
+0x000008bd: 01 DW_LNS_copy
             0x0000000000000559    113     10      1   0             0  is_stmt
 
 
-0x000008c8: 00 DW_LNE_set_address (0x000000000000055c)
-0x000008cf: 03 DW_LNS_advance_line (118)
-0x000008d1: 05 DW_LNS_set_column (16)
-0x000008d3: 01 DW_LNS_copy
+0x000008be: 00 DW_LNE_set_address (0x000000000000055c)
+0x000008c5: 03 DW_LNS_advance_line (118)
+0x000008c7: 05 DW_LNS_set_column (16)
+0x000008c9: 01 DW_LNS_copy
             0x000000000000055c    118     16      1   0             0  is_stmt
 
 
-0x000008d4: 00 DW_LNE_set_address (0x0000000000000565)
-0x000008db: 03 DW_LNS_advance_line (119)
-0x000008dd: 05 DW_LNS_set_column (10)
-0x000008df: 01 DW_LNS_copy
+0x000008ca: 00 DW_LNE_set_address (0x0000000000000565)
+0x000008d1: 03 DW_LNS_advance_line (119)
+0x000008d3: 05 DW_LNS_set_column (10)
+0x000008d5: 01 DW_LNS_copy
             0x0000000000000565    119     10      1   0             0  is_stmt
 
 
-0x000008e0: 00 DW_LNE_set_address (0x0000000000000567)
-0x000008e7: 05 DW_LNS_set_column (18)
-0x000008e9: 06 DW_LNS_negate_stmt
-0x000008ea: 01 DW_LNS_copy
+0x000008d6: 00 DW_LNE_set_address (0x0000000000000567)
+0x000008dd: 05 DW_LNS_set_column (18)
+0x000008df: 06 DW_LNS_negate_stmt
+0x000008e0: 01 DW_LNS_copy
             0x0000000000000567    119     18      1   0             0 
 
 
-0x000008eb: 00 DW_LNE_set_address (0x0000000000000570)
-0x000008f2: 05 DW_LNS_set_column (10)
-0x000008f4: 01 DW_LNS_copy
+0x000008e1: 00 DW_LNE_set_address (0x0000000000000570)
+0x000008e8: 05 DW_LNS_set_column (10)
+0x000008ea: 01 DW_LNS_copy
             0x0000000000000570    119     10      1   0             0 
 
 
-0x000008f5: 00 DW_LNE_set_address (0x0000000000000572)
-0x000008fc: 05 DW_LNS_set_column (23)
-0x000008fe: 01 DW_LNS_copy
+0x000008eb: 00 DW_LNE_set_address (0x0000000000000572)
+0x000008f2: 05 DW_LNS_set_column (23)
+0x000008f4: 01 DW_LNS_copy
             0x0000000000000572    119     23      1   0             0 
 
 
-0x000008ff: 00 DW_LNE_set_address (0x0000000000000577)
-0x00000906: 03 DW_LNS_advance_line (118)
-0x00000908: 05 DW_LNS_set_column (16)
-0x0000090a: 06 DW_LNS_negate_stmt
-0x0000090b: 01 DW_LNS_copy
+0x000008f5: 00 DW_LNE_set_address (0x0000000000000577)
+0x000008fc: 03 DW_LNS_advance_line (118)
+0x000008fe: 05 DW_LNS_set_column (16)
+0x00000900: 06 DW_LNS_negate_stmt
+0x00000901: 01 DW_LNS_copy
             0x0000000000000577    118     16      1   0             0  is_stmt
 
 
-0x0000090c: 00 DW_LNE_set_address (0x0000000000000582)
-0x00000913: 05 DW_LNS_set_column (7)
-0x00000915: 06 DW_LNS_negate_stmt
-0x00000916: 01 DW_LNS_copy
+0x00000902: 00 DW_LNE_set_address (0x0000000000000582)
+0x00000909: 05 DW_LNS_set_column (7)
+0x0000090b: 06 DW_LNS_negate_stmt
+0x0000090c: 01 DW_LNS_copy
             0x0000000000000582    118      7      1   0             0 
 
 
-0x00000917: 00 DW_LNE_set_address (0x0000000000000588)
-0x0000091e: 03 DW_LNS_advance_line (122)
-0x00000920: 05 DW_LNS_set_column (16)
-0x00000922: 06 DW_LNS_negate_stmt
-0x00000923: 01 DW_LNS_copy
+0x0000090d: 00 DW_LNE_set_address (0x0000000000000588)
+0x00000914: 03 DW_LNS_advance_line (122)
+0x00000916: 05 DW_LNS_set_column (16)
+0x00000918: 06 DW_LNS_negate_stmt
+0x00000919: 01 DW_LNS_copy
             0x0000000000000588    122     16      1   0             0  is_stmt
 
 
-0x00000924: 00 DW_LNE_set_address (0x000000000000058d)
-0x0000092b: 05 DW_LNS_set_column (14)
-0x0000092d: 06 DW_LNS_negate_stmt
-0x0000092e: 01 DW_LNS_copy
+0x0000091a: 00 DW_LNE_set_address (0x000000000000058d)
+0x00000921: 05 DW_LNS_set_column (14)
+0x00000923: 06 DW_LNS_negate_stmt
+0x00000924: 01 DW_LNS_copy
             0x000000000000058d    122     14      1   0             0 
 
 
-0x0000092f: 00 DW_LNE_set_address (0x0000000000000596)
-0x00000936: 03 DW_LNS_advance_line (125)
-0x00000938: 05 DW_LNS_set_column (22)
-0x0000093a: 06 DW_LNS_negate_stmt
-0x0000093b: 01 DW_LNS_copy
+0x00000925: 00 DW_LNE_set_address (0x0000000000000596)
+0x0000092c: 03 DW_LNS_advance_line (125)
+0x0000092e: 05 DW_LNS_set_column (22)
+0x00000930: 06 DW_LNS_negate_stmt
+0x00000931: 01 DW_LNS_copy
             0x0000000000000596    125     22      1   0             0  is_stmt
 
 
-0x0000093c: 00 DW_LNE_set_address (0x00000000000005a3)
-0x00000943: 03 DW_LNS_advance_line (126)
-0x00000945: 05 DW_LNS_set_column (27)
-0x00000947: 01 DW_LNS_copy
+0x00000932: 00 DW_LNE_set_address (0x00000000000005a3)
+0x00000939: 03 DW_LNS_advance_line (126)
+0x0000093b: 05 DW_LNS_set_column (27)
+0x0000093d: 01 DW_LNS_copy
             0x00000000000005a3    126     27      1   0             0  is_stmt
 
 
-0x00000948: 00 DW_LNE_set_address (0x00000000000005ac)
-0x0000094f: 03 DW_LNS_advance_line (127)
-0x00000951: 05 DW_LNS_set_column (16)
-0x00000953: 01 DW_LNS_copy
+0x0000093e: 00 DW_LNE_set_address (0x00000000000005ac)
+0x00000945: 03 DW_LNS_advance_line (127)
+0x00000947: 05 DW_LNS_set_column (16)
+0x00000949: 01 DW_LNS_copy
             0x00000000000005ac    127     16      1   0             0  is_stmt
 
 
-0x00000954: 00 DW_LNE_set_address (0x00000000000005b4)
-0x0000095b: 05 DW_LNS_set_column (27)
-0x0000095d: 06 DW_LNS_negate_stmt
-0x0000095e: 01 DW_LNS_copy
+0x0000094a: 00 DW_LNE_set_address (0x00000000000005b4)
+0x00000951: 05 DW_LNS_set_column (27)
+0x00000953: 06 DW_LNS_negate_stmt
+0x00000954: 01 DW_LNS_copy
             0x00000000000005b4    127     27      1   0             0 
 
 
-0x0000095f: 00 DW_LNE_set_address (0x00000000000005b6)
-0x00000966: 05 DW_LNS_set_column (35)
-0x00000968: 01 DW_LNS_copy
+0x00000955: 00 DW_LNE_set_address (0x00000000000005b6)
+0x0000095c: 05 DW_LNS_set_column (35)
+0x0000095e: 01 DW_LNS_copy
             0x00000000000005b6    127     35      1   0             0 
 
 
-0x00000969: 00 DW_LNE_set_address (0x00000000000005bf)
-0x00000970: 05 DW_LNS_set_column (27)
-0x00000972: 01 DW_LNS_copy
+0x0000095f: 00 DW_LNE_set_address (0x00000000000005bf)
+0x00000966: 05 DW_LNS_set_column (27)
+0x00000968: 01 DW_LNS_copy
             0x00000000000005bf    127     27      1   0             0 
 
 
-0x00000973: 00 DW_LNE_set_address (0x00000000000005c4)
-0x0000097a: 05 DW_LNS_set_column (25)
-0x0000097c: 01 DW_LNS_copy
+0x00000969: 00 DW_LNE_set_address (0x00000000000005c4)
+0x00000970: 05 DW_LNS_set_column (25)
+0x00000972: 01 DW_LNS_copy
             0x00000000000005c4    127     25      1   0             0 
 
 
-0x0000097d: 00 DW_LNE_set_address (0x00000000000005c7)
-0x00000984: 03 DW_LNS_advance_line (126)
-0x00000986: 05 DW_LNS_set_column (27)
-0x00000988: 06 DW_LNS_negate_stmt
-0x00000989: 01 DW_LNS_copy
+0x00000973: 00 DW_LNE_set_address (0x00000000000005c7)
+0x0000097a: 03 DW_LNS_advance_line (126)
+0x0000097c: 05 DW_LNS_set_column (27)
+0x0000097e: 06 DW_LNS_negate_stmt
+0x0000097f: 01 DW_LNS_copy
             0x00000000000005c7    126     27      1   0             0  is_stmt
 
 
-0x0000098a: 00 DW_LNE_set_address (0x00000000000005cc)
-0x00000991: 05 DW_LNS_set_column (13)
-0x00000993: 06 DW_LNS_negate_stmt
-0x00000994: 01 DW_LNS_copy
+0x00000980: 00 DW_LNE_set_address (0x00000000000005cc)
+0x00000987: 05 DW_LNS_set_column (13)
+0x00000989: 06 DW_LNS_negate_stmt
+0x0000098a: 01 DW_LNS_copy
             0x00000000000005cc    126     13      1   0             0 
 
 
-0x00000995: 00 DW_LNE_set_address (0x00000000000005d4)
-0x0000099c: 03 DW_LNS_advance_line (128)
-0x0000099e: 06 DW_LNS_negate_stmt
-0x0000099f: 01 DW_LNS_copy
+0x0000098b: 00 DW_LNE_set_address (0x00000000000005d4)
+0x00000992: 03 DW_LNS_advance_line (128)
+0x00000994: 06 DW_LNS_negate_stmt
+0x00000995: 01 DW_LNS_copy
             0x00000000000005d4    128     13      1   0             0  is_stmt
 
 
-0x000009a0: 00 DW_LNE_set_address (0x00000000000005dc)
-0x000009a7: 05 DW_LNS_set_column (22)
-0x000009a9: 06 DW_LNS_negate_stmt
-0x000009aa: 01 DW_LNS_copy
+0x00000996: 00 DW_LNE_set_address (0x00000000000005dc)
+0x0000099d: 05 DW_LNS_set_column (22)
+0x0000099f: 06 DW_LNS_negate_stmt
+0x000009a0: 01 DW_LNS_copy
             0x00000000000005dc    128     22      1   0             0 
 
 
-0x000009ab: 00 DW_LNE_set_address (0x00000000000005e1)
-0x000009b2: 03 DW_LNS_advance_line (130)
-0x000009b4: 05 DW_LNS_set_column (16)
-0x000009b6: 06 DW_LNS_negate_stmt
-0x000009b7: 01 DW_LNS_copy
+0x000009a1: 00 DW_LNE_set_address (0x00000000000005e1)
+0x000009a8: 03 DW_LNS_advance_line (130)
+0x000009aa: 05 DW_LNS_set_column (16)
+0x000009ac: 06 DW_LNS_negate_stmt
+0x000009ad: 01 DW_LNS_copy
             0x00000000000005e1    130     16      1   0             0  is_stmt
 
 
-0x000009b8: 00 DW_LNE_set_address (0x00000000000005e9)
-0x000009bf: 05 DW_LNS_set_column (14)
-0x000009c1: 06 DW_LNS_negate_stmt
-0x000009c2: 01 DW_LNS_copy
+0x000009ae: 00 DW_LNE_set_address (0x00000000000005e9)
+0x000009b5: 05 DW_LNS_set_column (14)
+0x000009b7: 06 DW_LNS_negate_stmt
+0x000009b8: 01 DW_LNS_copy
             0x00000000000005e9    130     14      1   0             0 
 
 
-0x000009c3: 00 DW_LNE_set_address (0x00000000000005f8)
-0x000009ca: 05 DW_LNS_set_column (25)
-0x000009cc: 01 DW_LNS_copy
+0x000009b9: 00 DW_LNE_set_address (0x00000000000005f8)
+0x000009c0: 05 DW_LNS_set_column (25)
+0x000009c2: 01 DW_LNS_copy
             0x00000000000005f8    130     25      1   0             0 
 
 
-0x000009cd: 00 DW_LNE_set_address (0x00000000000005ff)
-0x000009d4: 03 DW_LNS_advance_line (133)
-0x000009d6: 05 DW_LNS_set_column (11)
-0x000009d8: 06 DW_LNS_negate_stmt
-0x000009d9: 01 DW_LNS_copy
+0x000009c3: 00 DW_LNE_set_address (0x00000000000005ff)
+0x000009ca: 03 DW_LNS_advance_line (133)
+0x000009cc: 05 DW_LNS_set_column (11)
+0x000009ce: 06 DW_LNS_negate_stmt
+0x000009cf: 01 DW_LNS_copy
             0x00000000000005ff    133     11      1   0             0  is_stmt
 
 
-0x000009da: 00 DW_LNE_set_address (0x0000000000000604)
-0x000009e1: 03 DW_LNS_advance_line (122)
-0x000009e3: 05 DW_LNS_set_column (16)
-0x000009e5: 01 DW_LNS_copy
+0x000009d0: 00 DW_LNE_set_address (0x0000000000000604)
+0x000009d7: 03 DW_LNS_advance_line (122)
+0x000009d9: 05 DW_LNS_set_column (16)
+0x000009db: 01 DW_LNS_copy
             0x0000000000000604    122     16      1   0             0  is_stmt
 
 
-0x000009e6: 00 DW_LNE_set_address (0x0000000000000609)
-0x000009ed: 05 DW_LNS_set_column (14)
-0x000009ef: 06 DW_LNS_negate_stmt
-0x000009f0: 01 DW_LNS_copy
+0x000009dc: 00 DW_LNE_set_address (0x0000000000000609)
+0x000009e3: 05 DW_LNS_set_column (14)
+0x000009e5: 06 DW_LNS_negate_stmt
+0x000009e6: 01 DW_LNS_copy
             0x0000000000000609    122     14      1   0             0 
 
 
-0x000009f1: 00 DW_LNE_set_address (0x000000000000060e)
-0x000009f8: 03 DW_LNS_advance_line (130)
-0x000009fa: 06 DW_LNS_negate_stmt
-0x000009fb: 01 DW_LNS_copy
-            0x000000000000060e    130     14      1   0             0  is_stmt
-
-
-0x000009fc: 00 DW_LNE_set_address (0x000000000000060f)
-0x00000a03: 03 DW_LNS_advance_line (110)
-0x00000a05: 05 DW_LNS_set_column (11)
-0x00000a07: 01 DW_LNS_copy
+0x000009e7: 00 DW_LNE_set_address (0x000000000000060f)
+0x000009ee: 03 DW_LNS_advance_line (110)
+0x000009f0: 05 DW_LNS_set_column (11)
+0x000009f2: 06 DW_LNS_negate_stmt
+0x000009f3: 01 DW_LNS_copy
             0x000000000000060f    110     11      1   0             0  is_stmt
 
 
-0x00000a08: 00 DW_LNE_set_address (0x0000000000000615)
-0x00000a0f: 03 DW_LNS_advance_line (138)
-0x00000a11: 05 DW_LNS_set_column (4)
-0x00000a13: 01 DW_LNS_copy
+0x000009f4: 00 DW_LNE_set_address (0x0000000000000615)
+0x000009fb: 03 DW_LNS_advance_line (138)
+0x000009fd: 05 DW_LNS_set_column (4)
+0x000009ff: 01 DW_LNS_copy
             0x0000000000000615    138      4      1   0             0  is_stmt
 
 
-0x00000a14: 00 DW_LNE_set_address (0x0000000000000619)
-0x00000a1b: 03 DW_LNS_advance_line (139)
-0x00000a1d: 01 DW_LNS_copy
+0x00000a00: 00 DW_LNE_set_address (0x0000000000000619)
+0x00000a07: 03 DW_LNS_advance_line (139)
+0x00000a09: 01 DW_LNS_copy
             0x0000000000000619    139      4      1   0             0  is_stmt
 
 
-0x00000a1e: 00 DW_LNE_set_address (0x0000000000000629)
-0x00000a25: 03 DW_LNS_advance_line (142)
-0x00000a27: 05 DW_LNS_set_column (20)
-0x00000a29: 01 DW_LNS_copy
+0x00000a0a: 00 DW_LNE_set_address (0x0000000000000629)
+0x00000a11: 03 DW_LNS_advance_line (142)
+0x00000a13: 05 DW_LNS_set_column (20)
+0x00000a15: 01 DW_LNS_copy
             0x0000000000000629    142     20      1   0             0  is_stmt
 
 
-0x00000a2a: 00 DW_LNE_set_address (0x0000000000000631)
-0x00000a31: 03 DW_LNS_advance_line (146)
-0x00000a33: 01 DW_LNS_copy
+0x00000a16: 00 DW_LNE_set_address (0x0000000000000631)
+0x00000a1d: 03 DW_LNS_advance_line (146)
+0x00000a1f: 01 DW_LNS_copy
             0x0000000000000631    146     20      1   0             0  is_stmt
 
 
-0x00000a34: 00 DW_LNE_set_address (0x0000000000000638)
-0x00000a3b: 03 DW_LNS_advance_line (147)
-0x00000a3d: 05 DW_LNS_set_column (7)
-0x00000a3f: 01 DW_LNS_copy
+0x00000a20: 00 DW_LNE_set_address (0x0000000000000638)
+0x00000a27: 03 DW_LNS_advance_line (147)
+0x00000a29: 05 DW_LNS_set_column (7)
+0x00000a2b: 01 DW_LNS_copy
             0x0000000000000638    147      7      1   0             0  is_stmt
 
 
-0x00000a40: 00 DW_LNE_set_address (0x000000000000063c)
-0x00000a47: 03 DW_LNS_advance_line (143)
-0x00000a49: 05 DW_LNS_set_column (11)
-0x00000a4b: 01 DW_LNS_copy
+0x00000a2c: 00 DW_LNE_set_address (0x000000000000063c)
+0x00000a33: 03 DW_LNS_advance_line (143)
+0x00000a35: 05 DW_LNS_set_column (11)
+0x00000a37: 01 DW_LNS_copy
             0x000000000000063c    143     11      1   0             0  is_stmt
 
 
-0x00000a4c: 00 DW_LNE_set_address (0x0000000000000640)
-0x00000a53: 05 DW_LNS_set_column (20)
-0x00000a55: 06 DW_LNS_negate_stmt
-0x00000a56: 01 DW_LNS_copy
+0x00000a38: 00 DW_LNE_set_address (0x0000000000000640)
+0x00000a3f: 05 DW_LNS_set_column (20)
+0x00000a41: 06 DW_LNS_negate_stmt
+0x00000a42: 01 DW_LNS_copy
             0x0000000000000640    143     20      1   0             0 
 
 
-0x00000a57: 00 DW_LNE_set_address (0x0000000000000645)
-0x00000a5e: 05 DW_LNS_set_column (11)
-0x00000a60: 01 DW_LNS_copy
+0x00000a43: 00 DW_LNE_set_address (0x0000000000000645)
+0x00000a4a: 05 DW_LNS_set_column (11)
+0x00000a4c: 01 DW_LNS_copy
             0x0000000000000645    143     11      1   0             0 
 
 
-0x00000a61: 00 DW_LNE_set_address (0x000000000000064c)
-0x00000a68: 03 DW_LNS_advance_line (141)
-0x00000a6a: 05 DW_LNS_set_column (4)
-0x00000a6c: 06 DW_LNS_negate_stmt
-0x00000a6d: 01 DW_LNS_copy
+0x00000a4d: 00 DW_LNE_set_address (0x000000000000064c)
+0x00000a54: 03 DW_LNS_advance_line (141)
+0x00000a56: 05 DW_LNS_set_column (4)
+0x00000a58: 06 DW_LNS_negate_stmt
+0x00000a59: 01 DW_LNS_copy
             0x000000000000064c    141      4      1   0             0  is_stmt
 
 
-0x00000a6e: 00 DW_LNE_set_address (0x0000000000000652)
-0x00000a75: 03 DW_LNS_advance_line (159)
-0x00000a77: 01 DW_LNS_copy
+0x00000a5a: 00 DW_LNE_set_address (0x0000000000000652)
+0x00000a61: 03 DW_LNS_advance_line (159)
+0x00000a63: 01 DW_LNS_copy
             0x0000000000000652    159      4      1   0             0  is_stmt
 
 
-0x00000a78: 00 DW_LNE_set_address (0x0000000000000669)
-0x00000a7f: 03 DW_LNS_advance_line (161)
-0x00000a81: 05 DW_LNS_set_column (1)
-0x00000a83: 01 DW_LNS_copy
+0x00000a64: 00 DW_LNE_set_address (0x0000000000000669)
+0x00000a6b: 03 DW_LNS_advance_line (161)
+0x00000a6d: 05 DW_LNS_set_column (1)
+0x00000a6f: 01 DW_LNS_copy
             0x0000000000000669    161      1      1   0             0  is_stmt
 
 
-0x00000a84: 00 DW_LNE_set_address (0x0000000000000673)
-0x00000a8b: 00 DW_LNE_end_sequence
+0x00000a70: 00 DW_LNE_set_address (0x0000000000000673)
+0x00000a77: 00 DW_LNE_end_sequence
             0x0000000000000673    161      1      1   0             0  is_stmt end_sequence
 
 
@@ -6861,7 +6849,7 @@ file_names[  4]:
  ;; custom section ".debug_loc", size 1073
  ;; custom section ".debug_ranges", size 88
  ;; custom section ".debug_abbrev", size 333
- ;; custom section ".debug_line", size 2702
+ ;; custom section ".debug_line", size 2682
  ;; custom section ".debug_str", size 434
  ;; custom section "producers", size 135
 )
diff --git a/test/passes/fib_nonzero-low-pc_dwarf.bin.txt b/test/passes/fib_nonzero-low-pc_dwarf.bin.txt
index b8c4c76a7..03935c482 100644
--- a/test/passes/fib_nonzero-low-pc_dwarf.bin.txt
+++ b/test/passes/fib_nonzero-low-pc_dwarf.bin.txt
@@ -365,7 +365,7 @@ Abbrev table for offset: 0x00000000
 
 0x00000079:     DW_TAG_lexical_block [5] *
                   DW_AT_low_pc [DW_FORM_addr]	(0x000000000000001b)
-                  DW_AT_high_pc [DW_FORM_data4]	(0x00000000)
+                  DW_AT_high_pc [DW_FORM_data4]	(0x00000033)
 
 0x00000082:       DW_TAG_variable [4]  
                     DW_AT_location [DW_FORM_sec_offset]	(0x00000093: