Auto merge of #112418 - ferrocene:pa-mir-opt-panic, r=ozkanonur,saethlin

Add support for targets without unwinding in `mir-opt`, and improve `--bless` for it

The main goal of this PR is to add support for targets without unwinding support in the `mir-opt` test suite, by adding the `EMIT_MIR_FOR_EACH_PANIC_STRATEGY` comment. Similarly to 32bit vs 64bit, when that comment is present, blessed output files will have the `.panic-unwind` or `.panic-abort` suffix, and the right one will be chosen depending on the target's panic strategy.

The `EMIT_MIR_FOR_EACH_PANIC_STRATEGY` comment replaced all the `ignore-wasm32` comments in the `mir-opt` test suite, as those comments were added due to `wasm32` being a target without unwinding support. The comment was also added on other tests that were only executed on x86 but were still panic strategy dependent.

The `mir-opt` suite was then blessed, which caused a ton of churn as most of the existing output files had to be renamed and (mostly) duplicated with the abort strategy.

---

After [asking on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/mir-opt.20tests.20and.20panic.3Dabort), the main concern about this change is it'd make blessing the `mir-opt` suite even harder, as you'd need to both bless it with an unwinding target and an aborting target. This exacerbated the current situation, where you'd need to bless it with a 32bit and a 64bit target already.

Because of that, this PR also makes significant enhancements to `--bless` for the `mir-opt` suite, where it will automatically bless the suite four times with different targets, while requiring minimal cross-compilation.

To handle the 32bit vs 64bit blessing, there is now an hardcoded list of target mapping between 32bit and 64bit. The goal of the list is to find a related target that will *probably* work without requiring additional cross-compilation toolchains on the system. If a mapping is found, bootstrap will bless the suite with both targets, otherwise just with the current target.

To handle the panic strategy blessing (abort vs unwind), I had to resort to what I call "synthetic targets". For each of the target we're blessing (so either the current one, or a 32bit and a 64bit depending on the previous paragraph), bootstrap will extract the JSON spec of the target and change it to include `"panic-strategy": "abort"`. It will then build the standard library with this synthetic target, and bless the `mir-opt` suite with it.

As a result of these changes, blessing the `mir-opt` suite will actually bless it two or four times with different targets, ensuring all possible variants are actually blessed.

---

This PR is best reviewed commit-by-commit.

r? `@jyn514`
cc `@saethlin` `@oli-obk`

1 files changed, 52 insertions, 0 deletions

diff --git a/tests/mir-opt/while_storage.while_loop.PreCodegen.after.panic-abort.mir b/tests/mir-opt/while_storage.while_loop.PreCodegen.after.panic-abort.mir
new file mode 100644
index 00000000000..c12f3591881
--- /dev/null
+++ b/tests/mir-opt/while_storage.while_loop.PreCodegen.after.panic-abort.mir
@@ -0,0 +1,52 @@
+// MIR for `while_loop` after PreCodegen
+
+fn while_loop(_1: bool) -> () {
+    debug c => _1;                       // in scope 0 at $DIR/while_storage.rs:+0:15: +0:16
+    let mut _0: ();                      // return place in scope 0 at $DIR/while_storage.rs:+0:24: +0:24
+    let mut _2: bool;                    // in scope 0 at $DIR/while_storage.rs:+1:11: +1:22
+    let mut _3: bool;                    // in scope 0 at $DIR/while_storage.rs:+2:12: +2:23
+
+    bb0: {
+        goto -> bb1;                     // scope 0 at $DIR/while_storage.rs:+1:5: +5:6
+    }
+
+    bb1: {
+        StorageLive(_2);                 // scope 0 at $DIR/while_storage.rs:+1:11: +1:22
+        _2 = get_bool(_1) -> [return: bb2, unwind unreachable]; // scope 0 at $DIR/while_storage.rs:+1:11: +1:22
+                                         // mir::Constant
+                                         // + span: $DIR/while_storage.rs:11:11: 11:19
+                                         // + literal: Const { ty: fn(bool) -> bool {get_bool}, val: Value(<ZST>) }
+    }
+
+    bb2: {
+        switchInt(move _2) -> [0: bb7, otherwise: bb3]; // scope 0 at $DIR/while_storage.rs:+1:11: +1:22
+    }
+
+    bb3: {
+        StorageLive(_3);                 // scope 0 at $DIR/while_storage.rs:+2:12: +2:23
+        _3 = get_bool(_1) -> [return: bb4, unwind unreachable]; // scope 0 at $DIR/while_storage.rs:+2:12: +2:23
+                                         // mir::Constant
+                                         // + span: $DIR/while_storage.rs:12:12: 12:20
+                                         // + literal: Const { ty: fn(bool) -> bool {get_bool}, val: Value(<ZST>) }
+    }
+
+    bb4: {
+        switchInt(move _3) -> [0: bb5, otherwise: bb6]; // scope 0 at $DIR/while_storage.rs:+2:12: +2:23
+    }
+
+    bb5: {
+        StorageDead(_3);                 // scope 0 at $DIR/while_storage.rs:+4:9: +4:10
+        StorageDead(_2);                 // scope 0 at $DIR/while_storage.rs:+5:5: +5:6
+        goto -> bb1;                     // scope 0 at $DIR/while_storage.rs:+1:5: +5:6
+    }
+
+    bb6: {
+        StorageDead(_3);                 // scope 0 at $DIR/while_storage.rs:+4:9: +4:10
+        goto -> bb7;                     // scope 0 at no-location
+    }
+
+    bb7: {
+        StorageDead(_2);                 // scope 0 at $DIR/while_storage.rs:+5:5: +5:6
+        return;                          // scope 0 at $DIR/while_storage.rs:+6:2: +6:2
+    }
+}