Maksim Panchenko 457b7f14b9 [BOLT] Fix debug info for input with continuous range. ... Summary: When we see a compilation unit with continuous range on input, it has two attributes: DW_AT_low_pc and DW_AT_high_pc. We convert the range to a non-continuous one and change the attributes to DW_AT_ranges and DW_AT_producer. However, gdb seems to expect every compilation unit to have a base address specified via DW_AT_low_pc, even when its value is always 0. Otherwise gdb will not show proper debug info for such modules. With this diff we produce DW_AT_ranges followed by DW_AT_low_pc. The problem is that the first attribute takes DW_FORM_sec_offset which is exactly 4 bytes, and in many cases we are left with 12 bytes to fill in. We used to fill this space with DW_AT_producer, which took an arbitrary-length field. For DW_AT_low_pc we can use a trick of using DW_FORM_udata (unsigned ULEB128 encoded integer) which can take up to 12 bytes, even when the value is 0. (cherry picked from FBD5109798)		2017-05-22 17:17:04 -07:00
bolt	[BOLT] Fix debug info for input with continuous range.	2017-05-22 17:17:04 -07:00