[llvm] [SimplifyCFG] Don't hoist a musttail call separately from the terminator (PR #207094)

[Jon Roelofs via llvm-commits]

================
@@ -101,3 +101,34 @@ if.else:
 if.end:
   ret void
 }
+
+declare ptr @callee(ptr, i32, i32)
+
+define ptr @dont_hoist_musttail_past_pseudoprobe(ptr %a, i32 %b, i32 %c) {
+; CHECK-LABEL: @dont_hoist_musttail_past_pseudoprobe(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[COND:%.*]] = icmp eq i32 [[C:%.*]], 0
+; CHECK-NEXT:    br i1 [[COND]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    call void @llvm.pseudoprobe(i64 3, i64 1, i32 0, i64 -1)
+; CHECK-NEXT:    [[CALL:%.*]] = musttail call ptr @callee(ptr [[A:%.*]], i32 [[B:%.*]], i32 [[C]])
+; CHECK-NEXT:    ret ptr [[CALL]]
+; CHECK:       if.else:
+; CHECK-NEXT:    call void @llvm.pseudoprobe(i64 3, i64 2, i32 0, i64 -1)
+; CHECK-NEXT:    [[CALL2:%.*]] = musttail call ptr @callee(ptr [[A]], i32 [[B]], i32 [[C]])
+; CHECK-NEXT:    ret ptr [[CALL2]]
+;
+entry:
+  %cond = icmp eq i32 %c, 0
+  br i1 %cond, label %if.then, label %if.else
+
+if.then:
+  call void @llvm.pseudoprobe(i64 3, i64 1, i32 0, i64 -1)
+  %call = musttail call ptr @callee(ptr %a, i32 %b, i32 %c)
+  ret ptr %call
+
+if.else:
+  call void @llvm.pseudoprobe(i64 3, i64 2, i32 0, i64 -1)
+  %call2 = musttail call ptr @callee(ptr %a, i32 %b, i32 %c)
+  ret ptr %call2
+}
----------------
jroelofs wrote:

Do we have any positive versions of this test? It would also be useful to have coverage of the `all_of`, e.g. some cases where the two calls differ in their musttail-ness.

https://github.com/llvm/llvm-project/pull/207094