Jubilee 864eba9fb1
Rollup merge of #136895 - maurer:fix-enum-discr, r=nikic
debuginfo: Set bitwidth appropriately in enum variant tags

Previously, we unconditionally set the bitwidth to 128-bits, the largest an enum would possibly be. Then, LLVM would cut down the constant by chopping off leading zeroes before emitting the DWARF. LLVM only supported 64-bit enumerators, so this would also have occasionally resulted in truncated data.

LLVM added support for 128-bit enumerators in llvm/llvm-project#125578

That patchset trusts the constant to describe how wide the variant tag is, so the high 64-bits of zeros are considered potentially load-bearing.

As a result, we went from emitting tags that looked like:
DW_AT_discr_value     (0xfe)

(because `dwarf::BestForm` selected `data1`)

to emitting tags that looked like:
DW_AT_discr_value	(<0x10> fe ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 )

This makes the `DW_AT_discr_value` encode at the bitwidth of the tag, which:
1. Is probably closer to our intentions in terms of describing the data.
2. Doesn't invoke the 128-bit support which may not be supported by all debuggers / downstream tools.
3. Will result in smaller debug information.
2025-02-13 17:46:08 -08:00
..
2024-05-31 15:56:43 +10:00
2024-10-06 18:12:25 +02:00
2024-05-31 15:56:43 +10:00
2025-01-28 19:10:24 +03:00
2024-05-31 15:56:43 +10:00
2024-05-31 15:56:43 +10:00
2024-09-09 19:39:43 -07:00
2024-05-31 15:56:43 +10:00
2024-05-31 15:56:43 +10:00
2024-05-31 15:56:43 +10:00
2024-04-11 21:42:35 -04:00
2024-05-31 15:56:43 +10:00
2024-05-31 15:56:43 +10:00
2024-04-24 13:12:33 +01:00
2024-09-09 19:39:43 -07:00
2025-02-03 10:39:32 -05:00
2024-05-31 15:56:43 +10:00
2024-05-31 15:56:43 +10:00
2024-05-31 15:56:43 +10:00
2024-05-03 14:32:08 +02:00
2024-05-31 15:56:43 +10:00
2024-07-14 13:48:29 +03:00
2024-05-31 15:56:43 +10:00
2024-07-14 13:48:29 +03:00
2024-12-10 21:41:05 +01:00
2024-05-31 15:56:43 +10:00
2024-07-14 13:48:29 +03:00
2024-05-31 15:56:43 +10:00
2025-01-21 08:27:30 +00:00
2024-08-07 00:41:48 -04:00
2024-05-31 15:56:43 +10:00
2024-09-09 19:39:43 -07:00

The files here use the LLVM FileCheck framework, documented at https://llvm.org/docs/CommandGuide/FileCheck.html.

One extension worth noting is the use of revisions as custom prefixes for FileCheck. If your codegen test has different behavior based on the chosen target or different compiler flags that you want to exercise, you can use a revisions annotation, like so:

// revisions: aaa bbb
// [bbb] compile-flags: --flags-for-bbb

After specifying those variations, you can write different expected, or explicitly unexpected output by using <prefix>-SAME: and <prefix>-NOT:, like so:

// CHECK: expected code
// aaa-SAME: emitted-only-for-aaa
// aaa-NOT:                        emitted-only-for-bbb
// bbb-NOT:  emitted-only-for-aaa
// bbb-SAME:                       emitted-only-for-bbb