Auto merge of #127234 - ZhuUx:inlined-expr, r=davidtwco,Zalathar

[Coverage][MCDC] Group mcdc tests and fix panic when generating mcdc code for inlined expressions.

### Changes

1. Group all mcdc tests to one directory.
2. Since mcdc instruments different mappings for boolean expressions with normal branch coverage as #125766 introduces, it would be better also trace branch coverage results in mcdc tests.
3. So far rustc does not call `CoverageInfoBuilderMethods::init_coverage` for inlined functions. As a result, it could panic if it tries to instrument mcdc statements for inlined functions due to uninitialized cond bitmaps. We can reproduce this issue by current nightly rustc and [the test](https://github.com/rust-lang/rust/pull/127234/files#diff-c81af6bf4869aa42f5c7334e3e86344475de362f673f54ce439ec75fcb5ac3e5) with flag `--release`. This patch fixes it.

1 files changed, 288 insertions, 0 deletions

diff --git a/tests/coverage/mcdc/if.coverage b/tests/coverage/mcdc/if.coverage
new file mode 100644
index 00000000000..91fff073d0c
--- /dev/null
+++ b/tests/coverage/mcdc/if.coverage
@@ -0,0 +1,288 @@
+   LL|       |#![feature(coverage_attribute)]
+   LL|       |//@ edition: 2021
+   LL|       |//@ min-llvm-version: 18
+   LL|       |//@ compile-flags: -Zcoverage-options=mcdc
+   LL|       |//@ llvm-cov-flags: --show-branches=count --show-mcdc
+   LL|       |
+   LL|      2|fn mcdc_check_neither(a: bool, b: bool) {
+   LL|      2|    if a && b {
+                          ^0
+  ------------------
+  |  Branch (LL:8): [True: 0, False: 2]
+  |  Branch (LL:13): [True: 0, False: 0]
+  ------------------
+  |---> MC/DC Decision Region (LL:8) to (LL:14)
+  |
+  |  Number of Conditions: 2
+  |     Condition C1 --> (LL:8)
+  |     Condition C2 --> (LL:13)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2    Result
+  |  1 { F,  -  = F      }
+  |
+  |  C1-Pair: not covered
+  |  C2-Pair: not covered
+  |  MC/DC Coverage for Decision: 0.00%
+  |
+  ------------------
+   LL|      0|        say("a and b");
+   LL|      2|    } else {
+   LL|      2|        say("not both");
+   LL|      2|    }
+   LL|      2|}
+   LL|       |
+   LL|      2|fn mcdc_check_a(a: bool, b: bool) {
+   LL|      2|    if a && b {
+                          ^1
+  ------------------
+  |  Branch (LL:8): [True: 1, False: 1]
+  |  Branch (LL:13): [True: 1, False: 0]
+  ------------------
+  |---> MC/DC Decision Region (LL:8) to (LL:14)
+  |
+  |  Number of Conditions: 2
+  |     Condition C1 --> (LL:8)
+  |     Condition C2 --> (LL:13)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2    Result
+  |  1 { F,  -  = F      }
+  |  2 { T,  T  = T      }
+  |
+  |  C1-Pair: covered: (1,2)
+  |  C2-Pair: not covered
+  |  MC/DC Coverage for Decision: 50.00%
+  |
+  ------------------
+   LL|      1|        say("a and b");
+   LL|      1|    } else {
+   LL|      1|        say("not both");
+   LL|      1|    }
+   LL|      2|}
+   LL|       |
+   LL|      2|fn mcdc_check_b(a: bool, b: bool) {
+   LL|      2|    if a && b {
+  ------------------
+  |  Branch (LL:8): [True: 2, False: 0]
+  |  Branch (LL:13): [True: 1, False: 1]
+  ------------------
+  |---> MC/DC Decision Region (LL:8) to (LL:14)
+  |
+  |  Number of Conditions: 2
+  |     Condition C1 --> (LL:8)
+  |     Condition C2 --> (LL:13)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2    Result
+  |  1 { T,  F  = F      }
+  |  2 { T,  T  = T      }
+  |
+  |  C1-Pair: not covered
+  |  C2-Pair: covered: (1,2)
+  |  MC/DC Coverage for Decision: 50.00%
+  |
+  ------------------
+   LL|      1|        say("a and b");
+   LL|      1|    } else {
+   LL|      1|        say("not both");
+   LL|      1|    }
+   LL|      2|}
+   LL|       |
+   LL|      3|fn mcdc_check_both(a: bool, b: bool) {
+   LL|      3|    if a && b {
+                          ^2
+  ------------------
+  |  Branch (LL:8): [True: 2, False: 1]
+  |  Branch (LL:13): [True: 1, False: 1]
+  ------------------
+  |---> MC/DC Decision Region (LL:8) to (LL:14)
+  |
+  |  Number of Conditions: 2
+  |     Condition C1 --> (LL:8)
+  |     Condition C2 --> (LL:13)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2    Result
+  |  1 { F,  -  = F      }
+  |  2 { T,  F  = F      }
+  |  3 { T,  T  = T      }
+  |
+  |  C1-Pair: covered: (1,3)
+  |  C2-Pair: covered: (2,3)
+  |  MC/DC Coverage for Decision: 100.00%
+  |
+  ------------------
+   LL|      1|        say("a and b");
+   LL|      2|    } else {
+   LL|      2|        say("not both");
+   LL|      2|    }
+   LL|      3|}
+   LL|       |
+   LL|      4|fn mcdc_check_tree_decision(a: bool, b: bool, c: bool) {
+   LL|      4|    // This expression is intentionally written in a way
+   LL|      4|    // where 100% branch coverage indicates 100% mcdc coverage.
+   LL|      4|    if a && (b || c) {
+                           ^3   ^2
+  ------------------
+  |  Branch (LL:8): [True: 3, False: 1]
+  |  Branch (LL:14): [True: 1, False: 2]
+  |  Branch (LL:19): [True: 1, False: 1]
+  ------------------
+  |---> MC/DC Decision Region (LL:8) to (LL:21)
+  |
+  |  Number of Conditions: 3
+  |     Condition C1 --> (LL:8)
+  |     Condition C2 --> (LL:14)
+  |     Condition C3 --> (LL:19)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2, C3    Result
+  |  1 { F,  -,  -  = F      }
+  |  2 { T,  F,  F  = F      }
+  |  3 { T,  T,  -  = T      }
+  |  4 { T,  F,  T  = T      }
+  |
+  |  C1-Pair: covered: (1,3)
+  |  C2-Pair: covered: (2,3)
+  |  C3-Pair: covered: (2,4)
+  |  MC/DC Coverage for Decision: 100.00%
+  |
+  ------------------
+   LL|      2|        say("pass");
+   LL|      2|    } else {
+   LL|      2|        say("reject");
+   LL|      2|    }
+   LL|      4|}
+   LL|       |
+   LL|      4|fn mcdc_check_not_tree_decision(a: bool, b: bool, c: bool) {
+   LL|      4|    // Contradict to `mcdc_check_tree_decision`,
+   LL|      4|    // 100% branch coverage of this expression does not mean indicates 100% mcdc coverage.
+   LL|      4|    if (a || b) && c {
+                           ^1
+  ------------------
+  |  Branch (LL:9): [True: 3, False: 1]
+  |  Branch (LL:14): [True: 1, False: 0]
+  |  Branch (LL:20): [True: 2, False: 2]
+  ------------------
+  |---> MC/DC Decision Region (LL:8) to (LL:21)
+  |
+  |  Number of Conditions: 3
+  |     Condition C1 --> (LL:9)
+  |     Condition C2 --> (LL:14)
+  |     Condition C3 --> (LL:20)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2, C3    Result
+  |  1 { T,  -,  F  = F      }
+  |  2 { T,  -,  T  = T      }
+  |  3 { F,  T,  T  = T      }
+  |
+  |  C1-Pair: not covered
+  |  C2-Pair: not covered
+  |  C3-Pair: covered: (1,2)
+  |  MC/DC Coverage for Decision: 33.33%
+  |
+  ------------------
+   LL|      2|        say("pass");
+   LL|      2|    } else {
+   LL|      2|        say("reject");
+   LL|      2|    }
+   LL|      4|}
+   LL|       |
+   LL|      3|fn mcdc_nested_if(a: bool, b: bool, c: bool) {
+   LL|      3|    if a || b {
+                          ^0
+  ------------------
+  |  Branch (LL:8): [True: 3, False: 0]
+  |  Branch (LL:13): [True: 0, False: 0]
+  ------------------
+  |---> MC/DC Decision Region (LL:8) to (LL:14)
+  |
+  |  Number of Conditions: 2
+  |     Condition C1 --> (LL:8)
+  |     Condition C2 --> (LL:13)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2    Result
+  |  1 { T,  -  = T      }
+  |
+  |  C1-Pair: not covered
+  |  C2-Pair: not covered
+  |  MC/DC Coverage for Decision: 0.00%
+  |
+  ------------------
+   LL|      3|        say("a or b");
+   LL|      3|        if b && c {
+                              ^2
+  ------------------
+  |  Branch (LL:12): [True: 2, False: 1]
+  |  Branch (LL:17): [True: 1, False: 1]
+  ------------------
+  |---> MC/DC Decision Region (LL:12) to (LL:18)
+  |
+  |  Number of Conditions: 2
+  |     Condition C1 --> (LL:12)
+  |     Condition C2 --> (LL:17)
+  |
+  |  Executed MC/DC Test Vectors:
+  |
+  |     C1, C2    Result
+  |  1 { F,  -  = F      }
+  |  2 { T,  F  = F      }
+  |  3 { T,  T  = T      }
+  |
+  |  C1-Pair: covered: (1,3)
+  |  C2-Pair: covered: (2,3)
+  |  MC/DC Coverage for Decision: 100.00%
+  |
+  ------------------
+   LL|      1|            say("b and c");
+   LL|      2|        }
+   LL|      0|    } else {
+   LL|      0|        say("neither a nor b");
+   LL|      0|    }
+   LL|      3|}
+   LL|       |
+   LL|       |#[coverage(off)]
+   LL|       |fn main() {
+   LL|       |    mcdc_check_neither(false, false);
+   LL|       |    mcdc_check_neither(false, true);
+   LL|       |
+   LL|       |    mcdc_check_a(true, true);
+   LL|       |    mcdc_check_a(false, true);
+   LL|       |
+   LL|       |    mcdc_check_b(true, true);
+   LL|       |    mcdc_check_b(true, false);
+   LL|       |
+   LL|       |    mcdc_check_both(false, true);
+   LL|       |    mcdc_check_both(true, true);
+   LL|       |    mcdc_check_both(true, false);
+   LL|       |
+   LL|       |    mcdc_check_tree_decision(false, true, true);
+   LL|       |    mcdc_check_tree_decision(true, true, false);
+   LL|       |    mcdc_check_tree_decision(true, false, false);
+   LL|       |    mcdc_check_tree_decision(true, false, true);
+   LL|       |
+   LL|       |    mcdc_check_not_tree_decision(false, true, true);
+   LL|       |    mcdc_check_not_tree_decision(true, true, false);
+   LL|       |    mcdc_check_not_tree_decision(true, false, false);
+   LL|       |    mcdc_check_not_tree_decision(true, false, true);
+   LL|       |
+   LL|       |    mcdc_nested_if(true, false, true);
+   LL|       |    mcdc_nested_if(true, true, true);
+   LL|       |    mcdc_nested_if(true, true, false);
+   LL|       |}
+   LL|       |
+   LL|       |#[coverage(off)]
+   LL|       |fn say(message: &str) {
+   LL|       |    core::hint::black_box(message);
+   LL|       |}
+