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[SCCP] Check whether the default case is reachable #76295

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Merged
merged 2 commits into from
Jan 8, 2024
Merged

[SCCP] Check whether the default case is reachable #76295

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688480b
[SCCP] Add pre-commit tests for PR76085. NFC.
dtcxzyw Dec 23, 2023
c12b109
[SCCP] Check whether the default case is reachable
dtcxzyw Dec 23, 2023
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10 changes: 7 additions & 3 deletions llvm/lib/Transforms/Utils/SCCPSolver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -310,6 +310,7 @@ bool SCCPSolver::removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU,
new UnreachableInst(DefaultDest->getContext(), NewUnreachableBB);
}

DefaultDest->removePredecessor(BB);
SI->setDefaultDest(NewUnreachableBB);
Updates.push_back({DominatorTree::Delete, BB, DefaultDest});
Updates.push_back({DominatorTree::Insert, BB, NewUnreachableBB});
Expand Down Expand Up @@ -1063,14 +1064,17 @@ void SCCPInstVisitor::getFeasibleSuccessors(Instruction &TI,
// is ready.
if (SCValue.isConstantRange(/*UndefAllowed=*/false)) {
const ConstantRange &Range = SCValue.getConstantRange();
unsigned ReachableCaseCount = 0;
for (const auto &Case : SI->cases()) {
const APInt &CaseValue = Case.getCaseValue()->getValue();
if (Range.contains(CaseValue))
if (Range.contains(CaseValue)) {
Succs[Case.getSuccessorIndex()] = true;
++ReachableCaseCount;
}
}

// TODO: Determine whether default case is reachable.
Succs[SI->case_default()->getSuccessorIndex()] = true;
Succs[SI->case_default()->getSuccessorIndex()] =
Range.isSizeLargerThan(ReachableCaseCount);
return;
}

Expand Down
91 changes: 79 additions & 12 deletions llvm/test/Transforms/SCCP/switch.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@
; Make sure we always consider the default edge executable for a switch
; with no cases.
declare void @foo()
declare i32 @g(i32)

define void @test1() {
; CHECK-LABEL: @test1(
; CHECK-NEXT: switch i32 undef, label [[D:%.*]] [
Expand Down Expand Up @@ -115,17 +117,16 @@ switch.1:
ret i32 %phi
}

; TODO: Determine that the default destination is dead.
define i32 @test_local_range(ptr %p) {
; CHECK-LABEL: @test_local_range(
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
; CHECK-NEXT: switch i32 [[X]], label [[SWITCH_DEFAULT:%.*]] [
; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[SWITCH_0:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 2, label [[SWITCH_2:%.*]]
; CHECK-NEXT: ]
; CHECK: switch.default:
; CHECK-NEXT: ret i32 -1
; CHECK: default.unreachable:
; CHECK-NEXT: unreachable
; CHECK: switch.0:
; CHECK-NEXT: ret i32 0
; CHECK: switch.1:
Expand Down Expand Up @@ -161,14 +162,14 @@ switch.3:
define i32 @test_duplicate_successors(ptr %p) {
; CHECK-LABEL: @test_duplicate_successors(
; CHECK-NEXT: [[X:%.*]] = load i32, ptr [[P:%.*]], align 4, !range [[RNG0]]
; CHECK-NEXT: switch i32 [[X]], label [[SWITCH_DEFAULT:%.*]] [
; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[SWITCH_0:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_0]]
; CHECK-NEXT: i32 2, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 3, label [[SWITCH_1]]
; CHECK-NEXT: ]
; CHECK: switch.default:
; CHECK-NEXT: ret i32 -1
; CHECK: default.unreachable:
; CHECK-NEXT: unreachable
; CHECK: switch.0:
; CHECK-NEXT: ret i32 0
; CHECK: switch.1:
Expand Down Expand Up @@ -201,13 +202,13 @@ switch.2:
; range information.
define internal i32 @test_ip_range(i32 %x) {
; CHECK-LABEL: @test_ip_range(
; CHECK-NEXT: switch i32 [[X:%.*]], label [[SWITCH_DEFAULT:%.*]] [
; CHECK-NEXT: switch i32 [[X:%.*]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 3, label [[SWITCH_3:%.*]]
; CHECK-NEXT: i32 1, label [[SWITCH_1:%.*]]
; CHECK-NEXT: i32 2, label [[SWITCH_2:%.*]]
; CHECK-NEXT: ], !prof [[PROF1:![0-9]+]]
; CHECK: switch.default:
; CHECK-NEXT: ret i32 -1
; CHECK: default.unreachable:
; CHECK-NEXT: unreachable
; CHECK: switch.1:
; CHECK-NEXT: ret i32 1
; CHECK: switch.2:
Expand Down Expand Up @@ -240,8 +241,8 @@ switch.3:

define void @call_test_ip_range() {
; CHECK-LABEL: @call_test_ip_range(
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @test_ip_range(i32 1)
; CHECK-NEXT: [[TMP2:%.*]] = call i32 @test_ip_range(i32 3)
; CHECK-NEXT: [[TMP1:%.*]] = call i32 @test_ip_range(i32 1), !range [[RNG2:![0-9]+]]
; CHECK-NEXT: [[TMP2:%.*]] = call i32 @test_ip_range(i32 3), !range [[RNG2]]
; CHECK-NEXT: ret void
;
call i32 @test_ip_range(i32 1)
Expand Down Expand Up @@ -301,6 +302,72 @@ end.2:
ret i32 20
}

define i32 @test_default_unreachable_by_dom_cond(i32 %x) {
; CHECK-LABEL: @test_default_unreachable_by_dom_cond(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 4
; CHECK-NEXT: br i1 [[OR_COND]], label [[IF_THEN:%.*]], label [[RETURN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: switch i32 [[X]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 0, label [[SW_BB:%.*]]
; CHECK-NEXT: i32 1, label [[SW_BB2:%.*]]
; CHECK-NEXT: i32 2, label [[SW_BB4:%.*]]
; CHECK-NEXT: i32 3, label [[SW_BB6:%.*]]
; CHECK-NEXT: ]
; CHECK: sw.bb:
; CHECK-NEXT: [[CALL:%.*]] = tail call i32 @g(i32 2)
; CHECK-NEXT: br label [[RETURN]]
; CHECK: sw.bb2:
; CHECK-NEXT: [[CALL3:%.*]] = tail call i32 @g(i32 3)
; CHECK-NEXT: br label [[RETURN]]
; CHECK: sw.bb4:
; CHECK-NEXT: [[CALL5:%.*]] = tail call i32 @g(i32 4)
; CHECK-NEXT: br label [[RETURN]]
; CHECK: sw.bb6:
; CHECK-NEXT: [[CALL7:%.*]] = tail call i32 @g(i32 5)
; CHECK-NEXT: br label [[RETURN]]
; CHECK: default.unreachable:
; CHECK-NEXT: unreachable
; CHECK: return:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL7]], [[SW_BB6]] ], [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ], [ -23, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
entry:
%or.cond = icmp ult i32 %x, 4
br i1 %or.cond, label %if.then, label %return

if.then:
switch i32 %x, label %sw.epilog [
i32 0, label %sw.bb
i32 1, label %sw.bb2
i32 2, label %sw.bb4
i32 3, label %sw.bb6
]

sw.bb:
%call = tail call i32 @g(i32 2)
br label %return

sw.bb2:
%call3 = tail call i32 @g(i32 3)
br label %return

sw.bb4:
%call5 = tail call i32 @g(i32 4)
br label %return

sw.bb6:
%call7 = tail call i32 @g(i32 5)
br label %return

sw.epilog:
call void @foo()
br label %return

return:
%retval.0 = phi i32 [ %call7, %sw.bb6 ], [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ], [ -23, %sw.epilog ], [ -23, %entry ]
ret i32 %retval.0
}

declare void @llvm.assume(i1)

Expand Down