Auto merge of #111752 - dingxiangfei2009:lower-or-pattern, r=cjgillot

Lower `Or` pattern without allocating place

cc `@azizghuloum` `@cjgillot`

Related to #111583 and #111644

While reviewing #111644, it occurs to me that while we directly lower conjunctive predicates, which are connected with `&&`, into the desirable control flow, today we don't directly lower the disjunctive predicates, which are connected with `||`, in the similar fashion. Instead, we allocate a place for the boolean temporary to hold the result of evaluating the `||` expression.

Usually I would expect optimization at later stages to "inline" the evaluation of boolean predicates into simple CFG, but #111583 is an example where `&&` is failing to be optimized away and the assembly shows that both the expensive operands are evaluated. Therefore, I would like to make a small change to make the CFG a bit more straight-forward without invoking the `as_temp` machinery, and plus avoid allocating the place to hold the boolean result as well.

1 files changed, 4 insertions, 2 deletions

diff --git a/tests/mir-opt/lower_array_len.array_bound.NormalizeArrayLen.panic-abort.diff b/tests/mir-opt/lower_array_len.array_bound.NormalizeArrayLen.panic-abort.diff
index 6174d5259d0..5242c5f6afd 100644
--- a/tests/mir-opt/lower_array_len.array_bound.NormalizeArrayLen.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_bound.NormalizeArrayLen.panic-abort.diff
@@ -32,12 +32,12 @@
       bb1: {
           StorageDead(_6);
           _3 = Lt(move _4, move _5);
-          StorageDead(_5);
-          StorageDead(_4);
           switchInt(move _3) -> [0: bb4, otherwise: bb2];
       }
   
       bb2: {
+          StorageDead(_5);
+          StorageDead(_4);
           StorageLive(_8);
           _8 = _1;
           _9 = Len((*_2));
@@ -52,6 +52,8 @@
       }
   
       bb4: {
+          StorageDead(_5);
+          StorageDead(_4);
           _0 = const 42_u8;
           goto -> bb5;
       }