Reland "[CVP] Check whether the default case is reachable (#79993)" #96089
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This patch eliminates unreachable default cases using context-sensitive range information.
|
@llvm/pr-subscribers-llvm-transforms Author: Yingwei Zheng (dtcxzyw) ChangesThis patch reverts #81585 as #78582 has been landed. Full diff: https://github.com/llvm/llvm-project/pull/96089.diff 3 Files Affected:
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 50b5fdb567207..8fe2f8e12fa9b 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -366,6 +366,7 @@ static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
{ // Scope for SwitchInstProfUpdateWrapper. It must not live during
// ConstantFoldTerminator() as the underlying SwitchInst can be changed.
SwitchInstProfUpdateWrapper SI(*I);
+ unsigned ReachableCaseCount = 0;
for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
ConstantInt *Case = CI->getCaseValue();
@@ -402,6 +403,33 @@ static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
// Increment the case iterator since we didn't delete it.
++CI;
+ ++ReachableCaseCount;
+ }
+
+ BasicBlock *DefaultDest = SI->getDefaultDest();
+ if (ReachableCaseCount > 1 &&
+ !isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg())) {
+ ConstantRange CR = LVI->getConstantRangeAtUse(I->getOperandUse(0),
+ /*UndefAllowed*/ false);
+ // The default dest is unreachable if all cases are covered.
+ if (!CR.isSizeLargerThan(ReachableCaseCount)) {
+ BasicBlock *NewUnreachableBB =
+ BasicBlock::Create(BB->getContext(), "default.unreachable",
+ BB->getParent(), DefaultDest);
+ new UnreachableInst(BB->getContext(), NewUnreachableBB);
+
+ DefaultDest->removePredecessor(BB);
+ SI->setDefaultDest(NewUnreachableBB);
+
+ if (SuccessorsCount[DefaultDest] == 1)
+ DTU.applyUpdatesPermissive(
+ {{DominatorTree::Delete, BB, DefaultDest}});
+ DTU.applyUpdatesPermissive(
+ {{DominatorTree::Insert, BB, NewUnreachableBB}});
+
+ ++NumDeadCases;
+ Changed = true;
+ }
}
}
@@ -1283,6 +1311,12 @@ CorrelatedValuePropagationPass::run(Function &F, FunctionAnalysisManager &AM) {
if (!Changed) {
PA = PreservedAnalyses::all();
} else {
+#if defined(EXPENSIVE_CHECKS)
+ assert(DT->verify(DominatorTree::VerificationLevel::Full));
+#else
+ assert(DT->verify(DominatorTree::VerificationLevel::Fast));
+#endif // EXPENSIVE_CHECKS
+
PA.preserve<DominatorTreeAnalysis>();
PA.preserve<LazyValueAnalysis>();
}
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll b/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
index 701d867416a13..a3b1c89634835 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
@@ -442,7 +442,7 @@ define i32 @switch_range(i32 %cond) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[S:%.*]] = urem i32 [[COND:%.*]], 3
; CHECK-NEXT: [[S1:%.*]] = add nuw nsw i32 [[S]], 1
-; CHECK-NEXT: switch i32 [[S1]], label [[UNREACHABLE:%.*]] [
+; CHECK-NEXT: switch i32 [[S1]], label [[DEFAULT_UNREACHABLE:%.*]] [
; CHECK-NEXT: i32 1, label [[EXIT1:%.*]]
; CHECK-NEXT: i32 2, label [[EXIT2:%.*]]
; CHECK-NEXT: i32 3, label [[EXIT1]]
@@ -451,6 +451,8 @@ define i32 @switch_range(i32 %cond) {
; CHECK-NEXT: ret i32 1
; CHECK: exit2:
; CHECK-NEXT: ret i32 2
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: unreachable:
; CHECK-NEXT: ret i32 0
;
@@ -513,10 +515,9 @@ define i8 @switch_defaultdest_multipleuse(i8 %t0) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[O:%.*]] = or i8 [[T0:%.*]], 1
; CHECK-NEXT: [[R:%.*]] = srem i8 1, [[O]]
-; CHECK-NEXT: switch i8 [[R]], label [[EXIT:%.*]] [
-; CHECK-NEXT: i8 0, label [[EXIT]]
-; CHECK-NEXT: i8 1, label [[EXIT]]
-; CHECK-NEXT: ]
+; CHECK-NEXT: br label [[EXIT:%.*]]
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
; CHECK: exit:
; CHECK-NEXT: ret i8 0
;
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/switch.ll b/llvm/test/Transforms/CorrelatedValuePropagation/switch.ll
new file mode 100644
index 0000000000000..a0794d5efe932
--- /dev/null
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/switch.ll
@@ -0,0 +1,301 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt < %s -passes=correlated-propagation -S | FileCheck %s
+
+define i32 @test_unreachable_default(i32 noundef %num) {
+; CHECK-LABEL: define i32 @test_unreachable_default(
+; CHECK-SAME: i32 noundef [[NUM:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUB:%.*]] = add i32 [[NUM]], -120
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[SUB]], 3
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 2
+; CHECK-NEXT: switch i32 [[COND]], 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: ]
+; CHECK: sw.bb:
+; CHECK-NEXT: [[CALL:%.*]] = call i32 @call0()
+; CHECK-NEXT: br label [[CLEANUP:%.*]]
+; CHECK: sw.bb2:
+; CHECK-NEXT: [[CALL3:%.*]] = call i32 @call1()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: sw.bb4:
+; CHECK-NEXT: [[CALL5:%.*]] = call i32 @call2()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
+; CHECK: sw.default:
+; CHECK-NEXT: [[CALL6:%.*]] = call i32 @call3()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: cleanup:
+; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL6]], [[SW_DEFAULT:%.*]] ], [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+entry:
+ %sub = add i32 %num, -120
+ %cmp = icmp ult i32 %sub, 3
+ %cond = select i1 %cmp, i32 %sub, i32 2
+ switch i32 %cond, label %sw.default [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb2
+ i32 2, label %sw.bb4
+ ]
+
+sw.bb:
+ %call = call i32 @call0()
+ br label %cleanup
+
+sw.bb2:
+ %call3 = call i32 @call1()
+ br label %cleanup
+
+sw.bb4:
+ %call5 = call i32 @call2()
+ br label %cleanup
+
+sw.default:
+ %call6 = call i32 @call3()
+ br label %cleanup
+
+cleanup:
+ %retval.0 = phi i32 [ %call6, %sw.default ], [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ]
+ ret i32 %retval.0
+}
+
+define i32 @test_unreachable_default_shared_edge(i32 noundef %num) {
+; CHECK-LABEL: define i32 @test_unreachable_default_shared_edge(
+; CHECK-SAME: i32 noundef [[NUM:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUB:%.*]] = add i32 [[NUM]], -120
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[SUB]], 3
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 2
+; CHECK-NEXT: switch i32 [[COND]], 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: ]
+; CHECK: sw.bb:
+; CHECK-NEXT: [[CALL:%.*]] = call i32 @call0()
+; CHECK-NEXT: br label [[CLEANUP:%.*]]
+; CHECK: sw.bb2:
+; CHECK-NEXT: [[CALL3:%.*]] = call i32 @call1()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: default.unreachable:
+; CHECK-NEXT: unreachable
+; CHECK: sw.bb4:
+; CHECK-NEXT: [[CALL5:%.*]] = call i32 @call4(i32 [[SUB]])
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: cleanup:
+; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+entry:
+ %sub = add i32 %num, -120
+ %cmp = icmp ult i32 %sub, 3
+ %cond = select i1 %cmp, i32 %sub, i32 2
+ switch i32 %cond, label %sw.bb4 [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb2
+ i32 2, label %sw.bb4
+ ]
+
+sw.bb:
+ %call = call i32 @call0()
+ br label %cleanup
+
+sw.bb2:
+ %call3 = call i32 @call1()
+ br label %cleanup
+
+sw.bb4:
+ %val = phi i32 [ %sub, %entry ], [ %sub, %entry ]
+ %call5 = call i32 @call4(i32 %val)
+ br label %cleanup
+
+cleanup:
+ %retval.0 = phi i32 [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ]
+ ret i32 %retval.0
+}
+
+; Negative tests
+
+define i32 @test_reachable_default(i32 noundef %num) {
+; CHECK-LABEL: define i32 @test_reachable_default(
+; CHECK-SAME: i32 noundef [[NUM:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUB:%.*]] = add i32 [[NUM]], -120
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[SUB]], 3
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 4
+; CHECK-NEXT: switch i32 [[COND]], label [[SW_DEFAULT:%.*]] [
+; CHECK-NEXT: i32 0, label [[SW_BB:%.*]]
+; CHECK-NEXT: i32 1, label [[SW_BB2:%.*]]
+; CHECK-NEXT: i32 2, label [[SW_BB4:%.*]]
+; CHECK-NEXT: ]
+; CHECK: sw.bb:
+; CHECK-NEXT: [[CALL:%.*]] = call i32 @call0()
+; CHECK-NEXT: br label [[CLEANUP:%.*]]
+; CHECK: sw.bb2:
+; CHECK-NEXT: [[CALL3:%.*]] = call i32 @call1()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: sw.bb4:
+; CHECK-NEXT: [[CALL5:%.*]] = call i32 @call2()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: sw.default:
+; CHECK-NEXT: [[CALL6:%.*]] = call i32 @call3()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: cleanup:
+; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL6]], [[SW_DEFAULT]] ], [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+entry:
+ %sub = add i32 %num, -120
+ %cmp = icmp ult i32 %sub, 3
+ %cond = select i1 %cmp, i32 %sub, i32 4
+ switch i32 %cond, label %sw.default [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb2
+ i32 2, label %sw.bb4
+ ]
+
+sw.bb:
+ %call = call i32 @call0()
+ br label %cleanup
+
+sw.bb2:
+ %call3 = call i32 @call1()
+ br label %cleanup
+
+sw.bb4:
+ %call5 = call i32 @call2()
+ br label %cleanup
+
+sw.default:
+ %call6 = call i32 @call3()
+ br label %cleanup
+
+cleanup:
+ %retval.0 = phi i32 [ %call6, %sw.default ], [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ]
+ ret i32 %retval.0
+}
+
+define i32 @test_unreachable_default_cond_may_be_undef(i32 %num) {
+; CHECK-LABEL: define i32 @test_unreachable_default_cond_may_be_undef(
+; CHECK-SAME: i32 [[NUM:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUB:%.*]] = add i32 [[NUM]], -120
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[SUB]], 3
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 2
+; CHECK-NEXT: switch i32 [[COND]], label [[SW_DEFAULT:%.*]] [
+; CHECK-NEXT: i32 0, label [[SW_BB:%.*]]
+; CHECK-NEXT: i32 1, label [[SW_BB2:%.*]]
+; CHECK-NEXT: i32 2, label [[SW_BB4:%.*]]
+; CHECK-NEXT: ]
+; CHECK: sw.bb:
+; CHECK-NEXT: [[CALL:%.*]] = call i32 @call0()
+; CHECK-NEXT: br label [[CLEANUP:%.*]]
+; CHECK: sw.bb2:
+; CHECK-NEXT: [[CALL3:%.*]] = call i32 @call1()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: sw.bb4:
+; CHECK-NEXT: [[CALL5:%.*]] = call i32 @call2()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: sw.default:
+; CHECK-NEXT: [[CALL6:%.*]] = call i32 @call3()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: cleanup:
+; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL6]], [[SW_DEFAULT]] ], [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+entry:
+ %sub = add i32 %num, -120
+ %cmp = icmp ult i32 %sub, 3
+ %cond = select i1 %cmp, i32 %sub, i32 2
+ switch i32 %cond, label %sw.default [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb2
+ i32 2, label %sw.bb4
+ ]
+
+sw.bb:
+ %call = call i32 @call0()
+ br label %cleanup
+
+sw.bb2:
+ %call3 = call i32 @call1()
+ br label %cleanup
+
+sw.bb4:
+ %call5 = call i32 @call2()
+ br label %cleanup
+
+sw.default:
+ %call6 = call i32 @call3()
+ br label %cleanup
+
+cleanup:
+ %retval.0 = phi i32 [ %call6, %sw.default ], [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ]
+ ret i32 %retval.0
+}
+
+define i32 @test_default_is_already_unreachable(i32 %num) {
+; CHECK-LABEL: define i32 @test_default_is_already_unreachable(
+; CHECK-SAME: i32 [[NUM:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUB:%.*]] = add i32 [[NUM]], -120
+; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[SUB]], 3
+; CHECK-NEXT: [[COND:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 2
+; CHECK-NEXT: switch i32 [[COND]], label [[SW_DEFAULT:%.*]] [
+; CHECK-NEXT: i32 0, label [[SW_BB:%.*]]
+; CHECK-NEXT: i32 1, label [[SW_BB2:%.*]]
+; CHECK-NEXT: i32 2, label [[SW_BB4:%.*]]
+; CHECK-NEXT: ]
+; CHECK: sw.bb:
+; CHECK-NEXT: [[CALL:%.*]] = call i32 @call0()
+; CHECK-NEXT: br label [[CLEANUP:%.*]]
+; CHECK: sw.bb2:
+; CHECK-NEXT: [[CALL3:%.*]] = call i32 @call1()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: sw.bb4:
+; CHECK-NEXT: [[CALL5:%.*]] = call i32 @call2()
+; CHECK-NEXT: br label [[CLEANUP]]
+; CHECK: sw.default:
+; CHECK-NEXT: unreachable
+; CHECK: cleanup:
+; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[CALL5]], [[SW_BB4]] ], [ [[CALL3]], [[SW_BB2]] ], [ [[CALL]], [[SW_BB]] ]
+; CHECK-NEXT: ret i32 [[RETVAL_0]]
+;
+entry:
+ %sub = add i32 %num, -120
+ %cmp = icmp ult i32 %sub, 3
+ %cond = select i1 %cmp, i32 %sub, i32 2
+ switch i32 %cond, label %sw.default [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb2
+ i32 2, label %sw.bb4
+ ]
+
+sw.bb:
+ %call = call i32 @call0()
+ br label %cleanup
+
+sw.bb2:
+ %call3 = call i32 @call1()
+ br label %cleanup
+
+sw.bb4:
+ %call5 = call i32 @call2()
+ br label %cleanup
+
+sw.default:
+ unreachable
+
+cleanup:
+ %retval.0 = phi i32 [ %call5, %sw.bb4 ], [ %call3, %sw.bb2 ], [ %call, %sw.bb ]
+ ret i32 %retval.0
+}
+
+declare i32 @call0()
+declare i32 @call1()
+declare i32 @call2()
+declare i32 @call3()
+declare i32 @call4(i32)
|
DianQK
approved these changes
Jun 19, 2024
AlexisPerry
pushed a commit
to llvm-project-tlp/llvm-project
that referenced
this pull request
Jul 9, 2024
…" (llvm#96089) This patch reverts llvm#81585 as llvm#78582 has been landed. Now clang works well with reproducer llvm#79993 (comment).
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This patch reverts #81585 as #78582 has been landed.
Now clang works well with reproducer #79993 (comment).