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1; RUN: llc -mtriple=avr -print-after=finalize-isel -cgp-freq-ratio-to-skip-merge=10 < %s 2>&1 | FileCheck %s2 3; Because `switch` seems to trigger Machine Basic Blocks to be ordered4; in a different order than they were constructed, this exposes an5; error in the `expand-isel-pseudos` pass. Specifically, it thought we6; could always fallthrough to a newly-constructed MBB. However,7; there's no guarantee that either of the constructed MBBs need to8; occur immediately after the currently-focused one!9;10; This issue manifests in a CFG that looks something like this:11;12; %bb.2.finish:13; successors: %bb.5(?%) %bb.6(?%)14; Predecessors according to CFG: %bb.0 %bb.115; %0 = PHI %3, <%bb.0>, %5, <%bb.1>16; %7 = LDIRdK 217; %8 = LDIRdK 118; CPRdRr %2, %0, implicit-def %SREG19; BREQk <%bb.6>, implicit %SREG20;21; The code assumes it the fallthrough block after this is %bb.5, but22; it's actually %bb.3! To be proper, there should be an unconditional23; jump tying this block to %bb.5.24 25define i8 @select_must_add_unconditional_jump(i8 %arg0, i8 %arg1) unnamed_addr {26entry-block:27 switch i8 %arg0, label %dead [28 i8 0, label %zero29 i8 1, label %one30 ]31 32zero:33 br label %finish34 35one:36 br label %finish37 38finish:39 %predicate = phi i8 [ 50, %zero ], [ 100, %one ]40 %is_eq = icmp eq i8 %arg1, %predicate41 %result = select i1 %is_eq, i8 1, i8 242 ret i8 %result43 44dead:45 ret i8 046}47 48; This check may be a bit brittle, but the important thing is that the49; basic block containing `select` needs to contain explicit jumps to50; both successors.51 52; CHECK: bb.2.finish:53; CHECK: successors:54; CHECK: BREQk [[BRANCHED:%bb.[0-9]+]]55; CHECK: RJMPk [[DIRECT:%bb.[0-9]+]]56; CHECK-SAME-DAG: {{.*}}[[BRANCHED]]57; CHECK-SAME-DAG: {{.*}}[[DIRECT]]58; CHECK: bb.3.dead:59