Various crash reporting tools have a problem with the dwarf generated for

assembly source when it generates the TAG_subprogram dwarf debug info for
the labels that have nothing between them as in this bit of assembly source:

% cat ZeroLength.s 
_func1:
_func2:
 nop

One solution would be to not emit the subsequent labels with the same address
and use the next label with a different address or the end of the section for
the AT_high_pc value of the TAG_subprogram.

Turns out in llvm-mc it is not possible in all cases to determine of two
symbols have the same value at the point we put out the TAG_subprogram dwarf
debug info.

So we will have llvm-mc instead of putting out TAG_subprogram's put out
DW_TAG_label's.  And the DW_TAG_label does not have a AT_high_pc value which
avoids the problem.

This commit is only the functional change to make the diffs clear as to what is
really being changed.  The next commit will be to clean up the names of such
things like MCGenDwarfSubprogramEntry to something like MCGenDwarfLabelEntry.

rdar://10666925


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147860 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 8 deletions

diff --git a/test/MC/MachO/gen-dwarf.s b/test/MC/MachO/gen-dwarf.s
index a443d75ae0..4fbc32d295 100644
--- a/test/MC/MachO/gen-dwarf.s
+++ b/test/MC/MachO/gen-dwarf.s
@@ -7,6 +7,7 @@ _bar:
 L1:	leave
 	ret
 _foo:
+_baz:
 	nop
 .data
 _x:	.long 1
@@ -24,12 +25,11 @@ _x:	.long 1
 // CHECK: 	DW_AT_producer	DW_FORM_string
 // CHECK: 	DW_AT_language	DW_FORM_data2
 
-// CHECK: [2] DW_TAG_subprogram	DW_CHILDREN_yes
+// CHECK: [2] DW_TAG_label	DW_CHILDREN_yes
 // CHECK: 	DW_AT_name	DW_FORM_string
 // CHECK: 	DW_AT_decl_file	DW_FORM_data4
 // CHECK: 	DW_AT_decl_line	DW_FORM_data4
 // CHECK: 	DW_AT_low_pc	DW_FORM_addr
-// CHECK: 	DW_AT_high_pc	DW_FORM_addr
 // CHECK: 	DW_AT_prototyped	DW_FORM_flag
 
 // CHECK: [3] DW_TAG_unspecified_parameters	DW_CHILDREN_no
@@ -48,24 +48,33 @@ _x:	.long 1
 // CHECK:    DW_AT_producer [DW_FORM_string]	("llvm-mc (based on {{.*}})")
 // CHECK:    DW_AT_language [DW_FORM_data2]	(0x8001)
 
-// CHECK:    DW_TAG_subprogram [2] *
+// CHECK:    DW_TAG_label [2] *
 // CHECK:      DW_AT_name [DW_FORM_string]	("bar")
 // CHECK:      DW_AT_decl_file [DW_FORM_data4]	(0x00000001)
 // CHECK:      DW_AT_decl_line [DW_FORM_data4]	(0x00000005)
 // CHECK:      DW_AT_low_pc [DW_FORM_addr]	(0x0000000000000000)
-// CHECK:      DW_AT_high_pc [DW_FORM_addr]	(0x0000000000000007)
 // CHECK:      DW_AT_prototyped [DW_FORM_flag]	(0x00)
 
 // CHECK:      DW_TAG_unspecified_parameters [3]  
 
 // CHECK:      NULL
 
-// CHECK:    DW_TAG_subprogram [2] *
+// CHECK:    DW_TAG_label [2] *
 // CHECK:      DW_AT_name [DW_FORM_string]	("foo")
 // CHECK:      DW_AT_decl_file [DW_FORM_data4]	(0x00000001)
 // CHECK:      DW_AT_decl_line [DW_FORM_data4]	(0x00000009)
 // CHECK:      DW_AT_low_pc [DW_FORM_addr]	(0x0000000000000007)
-// CHECK:      DW_AT_high_pc [DW_FORM_addr]	(0x0000000000000008)
+// CHECK:      DW_AT_prototyped [DW_FORM_flag]	(0x00)
+
+// CHECK:      DW_TAG_unspecified_parameters [3]  
+
+// CHECK:      NULL
+
+// CHECK:    DW_TAG_label [2] *
+// CHECK:      DW_AT_name [DW_FORM_string]	("baz")
+// CHECK:      DW_AT_decl_file [DW_FORM_data4]	(0x00000001)
+// CHECK:      DW_AT_decl_line [DW_FORM_data4]	(0x0000000a)
+// CHECK:      DW_AT_low_pc [DW_FORM_addr]	(0x0000000000000007)
 // CHECK:      DW_AT_prototyped [DW_FORM_flag]	(0x00)
 
 // CHECK:      DW_TAG_unspecified_parameters [3]  
@@ -109,5 +118,5 @@ _x:	.long 1
 // CHECK: 0x0000000000000000      6      0      1   0  is_stmt
 // CHECK: 0x0000000000000005      7      0      1   0  is_stmt
 // CHECK: 0x0000000000000006      8      0      1   0  is_stmt
-// CHECK: 0x0000000000000007     10      0      1   0  is_stmt
-// CHECK: 0x0000000000000008     10      0      1   0  is_stmt end_sequence
+// CHECK: 0x0000000000000007     11      0      1   0  is_stmt
+// CHECK: 0x0000000000000008     11      0      1   0  is_stmt end_sequence