[lldb] Fix prologue size calculation for discontinuous functions (#131597)

When searching for the end of prologue, I'm only iterating through the
address range (~basic block) which contains the function entry point.
The reason for that is that even if some other range somehow contained
the end-of-prologue marker, the fact that it's in a different range
would imply it's reachable through some form of control flow, and that's
usually not a good place to set an function entry breakpoint.

Author: labath

lldb/source/Symbol/Function.cpp

@@ -662,10 +662,15 @@ uint32_t Function::GetPrologueByteSize() {
           }
         }
 
-        const addr_t func_start_file_addr =
-            m_range.GetBaseAddress().GetFileAddress();
-        const addr_t func_end_file_addr =
-            func_start_file_addr + m_range.GetByteSize();
+        AddressRange entry_range;
+        m_block.GetRangeContainingAddress(m_address, entry_range);
+
+        // Deliberately not starting at entry_range.GetBaseAddress() because the
+        // function entry point need not be the first address in the range.
+        const addr_t func_start_file_addr = m_address.GetFileAddress();
+        const addr_t range_end_file_addr =
+            entry_range.GetBaseAddress().GetFileAddress() +
+            entry_range.GetByteSize();
 
         // Now calculate the offset to pass the subsequent line 0 entries.
         uint32_t first_non_zero_line = prologue_end_line_idx;
@@ -677,7 +682,7 @@ uint32_t Function::GetPrologueByteSize() {
               break;
           }
           if (line_entry.range.GetBaseAddress().GetFileAddress() >=
-              func_end_file_addr)
+              range_end_file_addr)
             break;
 
           first_non_zero_line++;
@@ -692,15 +697,15 @@ uint32_t Function::GetPrologueByteSize() {
           }
         }
 
-        // Verify that this prologue end file address in the function's address
-        // range just to be sure
+        // Verify that this prologue end file address inside the function just
+        // to be sure
         if (func_start_file_addr < prologue_end_file_addr &&
-            prologue_end_file_addr < func_end_file_addr) {
+            prologue_end_file_addr < range_end_file_addr) {
           m_prologue_byte_size = prologue_end_file_addr - func_start_file_addr;
         }
 
         if (prologue_end_file_addr < line_zero_end_file_addr &&
-            line_zero_end_file_addr < func_end_file_addr) {
+            line_zero_end_file_addr < range_end_file_addr) {
           m_prologue_byte_size +=
               line_zero_end_file_addr - prologue_end_file_addr;
         }

lldb/test/Shell/SymbolFile/DWARF/x86/discontinuous-function.s

@@ -16,22 +16,32 @@ image lookup -v -n foo
 # CHECK-LABEL: image lookup -v -n foo
 # CHECK: 1 match found in {{.*}}
 # CHECK: Summary: input.o`foo
-# CHECK: Function: id = {{.*}}, name = "foo", ranges = [0x0000000000000000-0x000000000000000e)[0x0000000000000014-0x000000000000001c)
+# CHECK: Function: id = {{.*}}, name = "foo", ranges = [0x0000000000000000-0x000000000000000f)[0x0000000000000015-0x000000000000001d)
 
 image lookup -v --regex -n '^foo$'
 # CHECK-LABEL: image lookup -v --regex -n '^foo$'
 # CHECK: 1 match found in {{.*}}
 # CHECK: Summary: input.o`foo
-# CHECK: Function: id = {{.*}}, name = "foo", ranges = [0x0000000000000000-0x000000000000000e)[0x0000000000000014-0x000000000000001c)
+# CHECK: Function: id = {{.*}}, name = "foo", ranges = [0x0000000000000000-0x000000000000000f)[0x0000000000000015-0x000000000000001d)
 
 expr -- &foo
 # CHECK-LABEL: expr -- &foo
 # CHECK: (void (*)()) $0 = 0x0000000000000007
 
+breakpoint set --name foo --skip-prologue false
+# CHECK-LABEL: breakpoint set --name foo --skip-prologue false
+# CHECK: Breakpoint 1: where = input.o`foo at -:1, address = 0x0000000000000007
+
+breakpoint set --name foo --skip-prologue true
+# CHECK-LABEL: breakpoint set --name foo --skip-prologue true
+# CHECK: Breakpoint 2: where = input.o`foo + 1 at -:2, address = 0x0000000000000008
+
 #--- input.s
         .text
 
+        .file   0 "." "-"
 foo.__part.1:
+        .loc    0 10
         .cfi_startproc
         callq   bar
         jmp     foo.__part.3
@@ -41,7 +51,10 @@ foo.__part.1:
 
         .type   foo,@function
 foo:
+        .loc    0 1
         .cfi_startproc
+        nop
+        .loc    0 2 prologue_end
         cmpl    $0, %edi
         je      foo.__part.2
         jmp     foo.__part.1
@@ -51,13 +64,15 @@ foo:
 
 bar:
         .cfi_startproc
+        .loc    0 100
         movl    $47, %eax
         retq
         .cfi_endproc
 .Lbar_end:
         .size   bar, .Lbar_end-bar
 
 foo.__part.2:
+        .loc    0 20
         .cfi_startproc
         callq   baz
         jmp     foo.__part.3
@@ -66,6 +81,7 @@ foo.__part.2:
         .cfi_endproc
 
 foo.__part.3:
+        .loc    0 30
         .cfi_startproc
         retq
 .Lfoo.__part.3_end:
@@ -87,6 +103,8 @@ foo.__part.3:
         .byte   35                              # DW_FORM_rnglistx
         .byte   116                             # DW_AT_rnglists_base
         .byte   23                              # DW_FORM_sec_offset
+        .byte   16                              # DW_AT_stmt_list
+        .byte   23                              # DW_FORM_sec_offset
         .byte   0                               # EOM(1)
         .byte   0                               # EOM(2)
         .byte   2                               # Abbreviation Code
@@ -127,6 +145,7 @@ foo.__part.3:
         .quad   0                               # DW_AT_low_pc
         .byte   1                               # DW_AT_ranges
         .long   .Lrnglists_table_base0          # DW_AT_rnglists_base
+        .long   .Lline_table_start0             # DW_AT_stmt_list
         .byte   2                               # Abbrev [2] DW_TAG_subprogram
         .quad   bar                             # DW_AT_low_pc
         .quad   .Lbar_end                       # DW_AT_high_pc
@@ -183,3 +202,5 @@ foo.__part.3:
 .Ldebug_list_header_end0:
 
         .section        ".note.GNU-stack","",@progbits
+        .section        .debug_line,"",@progbits
+.Lline_table_start0: