59 lines
1.8 KiB
LLVM
59 lines
1.8 KiB
LLVM
; RUN: llc -march=avr -print-after=finalize-isel -cgp-freq-ratio-to-skip-merge=10 < %s 2>&1 | FileCheck %s
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; Because `switch` seems to trigger Machine Basic Blocks to be ordered
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; in a different order than they were constructed, this exposes an
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; error in the `expand-isel-pseudos` pass. Specifically, it thought we
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; could always fallthrough to a newly-constructed MBB. However,
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; there's no guarantee that either of the constructed MBBs need to
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; occur immediately after the currently-focused one!
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;
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; This issue manifests in a CFG that looks something like this:
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;
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; %bb.2.finish:
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; successors: %bb.5(?%) %bb.6(?%)
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; Predecessors according to CFG: %bb.0 %bb.1
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; %0 = PHI %3, <%bb.0>, %5, <%bb.1>
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; %7 = LDIRdK 2
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; %8 = LDIRdK 1
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; CPRdRr %2, %0, implicit-def %SREG
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; BREQk <%bb.6>, implicit %SREG
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;
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; The code assumes it the fallthrough block after this is %bb.5, but
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; it's actually %bb.3! To be proper, there should be an unconditional
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; jump tying this block to %bb.5.
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define i8 @select_must_add_unconditional_jump(i8 %arg0, i8 %arg1) unnamed_addr {
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entry-block:
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switch i8 %arg0, label %dead [
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i8 0, label %zero
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i8 1, label %one
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]
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zero:
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br label %finish
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one:
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br label %finish
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finish:
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%predicate = phi i8 [ 50, %zero ], [ 100, %one ]
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%is_eq = icmp eq i8 %arg1, %predicate
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%result = select i1 %is_eq, i8 1, i8 2
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ret i8 %result
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dead:
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ret i8 0
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}
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; This check may be a bit brittle, but the important thing is that the
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; basic block containing `select` needs to contain explicit jumps to
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; both successors.
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; CHECK: bb.2.finish:
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; CHECK: successors:
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; CHECK: BREQk [[BRANCHED:%bb.[0-9]+]]
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; CHECK: RJMPk [[DIRECT:%bb.[0-9]+]]
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; CHECK-SAME-DAG: {{.*}}[[BRANCHED]]
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; CHECK-SAME-DAG: {{.*}}[[DIRECT]]
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; CHECK: bb.3.dead:
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