[llvm] 9934a5b - [CVP] processSwitch: Remove default case when switch cover all possible values.
Jun Ma via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 17 19:23:23 PDT 2021
Author: Jun Ma
Date: 2021-08-18T10:23:13+08:00
New Revision: 9934a5b2ed5aa6e6bbb2e55c3cd98839722c226e
URL: https://github.com/llvm/llvm-project/commit/9934a5b2ed5aa6e6bbb2e55c3cd98839722c226e
DIFF: https://github.com/llvm/llvm-project/commit/9934a5b2ed5aa6e6bbb2e55c3cd98839722c226e.diff
LOG: [CVP] processSwitch: Remove default case when switch cover all possible values.
Differential Revision: https://reviews.llvm.org/D106056
Added:
Modified:
llvm/include/llvm/Transforms/Utils/Local.h
llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
llvm/lib/Transforms/Utils/Local.cpp
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index 97686d7d5f2f..f003615eca78 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -55,6 +55,7 @@ class MDNode;
class MemorySSAUpdater;
class PHINode;
class StoreInst;
+class SwitchInst;
class TargetLibraryInfo;
class TargetTransformInfo;
@@ -236,6 +237,10 @@ CallInst *createCallMatchingInvoke(InvokeInst *II);
/// This function converts the specified invoek into a normall call.
void changeToCall(InvokeInst *II, DomTreeUpdater *DTU = nullptr);
+/// This function removes the default destination from the specified switch.
+void createUnreachableSwitchDefault(SwitchInst *Switch,
+ DomTreeUpdater *DTU = nullptr);
+
///===---------------------------------------------------------------------===//
/// Dbg Intrinsic utilities
///
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index 36cbd42a5fdd..cd38ce96e287 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -341,7 +341,13 @@ static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
// ConstantFoldTerminator() as the underlying SwitchInst can be changed.
SwitchInstProfUpdateWrapper SI(*I);
- for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
+ APInt Low =
+ APInt::getSignedMaxValue(Cond->getType()->getScalarSizeInBits());
+ APInt High =
+ APInt::getSignedMinValue(Cond->getType()->getScalarSizeInBits());
+
+ SwitchInst::CaseIt CI = SI->case_begin();
+ for (auto CE = SI->case_end(); CI != CE;) {
ConstantInt *Case = CI->getCaseValue();
LazyValueInfo::Tristate State =
LVI->getPredicateAt(CmpInst::ICMP_EQ, Cond, Case, I,
@@ -374,9 +380,28 @@ static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
break;
}
+ // Get Lower/Upper bound from switch cases.
+ Low = APIntOps::smin(Case->getValue(), Low);
+ High = APIntOps::smax(Case->getValue(), High);
+
// Increment the case iterator since we didn't delete it.
++CI;
}
+
+ // Try to simplify default case as unreachable
+ if (CI == SI->case_end() && SI->getNumCases() != 0 &&
+ !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg())) {
+ const ConstantRange SIRange =
+ LVI->getConstantRange(SI->getCondition(), SI);
+
+ // If the numbered switch cases cover the entire range of the condition,
+ // then the default case is not reachable.
+ if (SIRange.getSignedMin() == Low && SIRange.getSignedMax() == High &&
+ SI->getNumCases() == High - Low + 1) {
+ createUnreachableSwitchDefault(SI, &DTU);
+ Changed = true;
+ }
+ }
}
if (Changed)
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 590600eec26c..8e19a4829710 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -2182,6 +2182,30 @@ void llvm::changeToCall(InvokeInst *II, DomTreeUpdater *DTU) {
DTU->applyUpdates({{DominatorTree::Delete, BB, UnwindDestBB}});
}
+void llvm::createUnreachableSwitchDefault(SwitchInst *Switch,
+ DomTreeUpdater *DTU) {
+ LLVM_DEBUG(dbgs() << "Switch default is dead.\n");
+ auto *BB = Switch->getParent();
+ BasicBlock *NewDefaultBlock = SplitBlockPredecessors(
+ Switch->getDefaultDest(), Switch->getParent(), "", DTU);
+ auto *OrigDefaultBlock = Switch->getDefaultDest();
+ Switch->setDefaultDest(&*NewDefaultBlock);
+ if (DTU)
+ DTU->applyUpdates({{DominatorTree::Insert, BB, &*NewDefaultBlock},
+ {DominatorTree::Delete, BB, OrigDefaultBlock}});
+
+ SplitBlock(&*NewDefaultBlock, &NewDefaultBlock->front(), DTU);
+ SmallVector<DominatorTree::UpdateType, 2> Updates;
+ if (DTU)
+ for (auto *Successor : successors(NewDefaultBlock))
+ Updates.push_back({DominatorTree::Delete, NewDefaultBlock, Successor});
+ auto *NewTerminator = NewDefaultBlock->getTerminator();
+ new UnreachableInst(Switch->getContext(), NewTerminator);
+ NewTerminator->eraseFromParent();
+ if (DTU)
+ DTU->applyUpdates(Updates);
+}
+
BasicBlock *llvm::changeToInvokeAndSplitBasicBlock(CallInst *CI,
BasicBlock *UnwindEdge,
DomTreeUpdater *DTU) {
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 847fdd760d2f..8f459966dfba 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -4743,29 +4743,6 @@ static bool CasesAreContiguous(SmallVectorImpl<ConstantInt *> &Cases) {
return true;
}
-static void createUnreachableSwitchDefault(SwitchInst *Switch,
- DomTreeUpdater *DTU) {
- LLVM_DEBUG(dbgs() << "SimplifyCFG: switch default is dead.\n");
- auto *BB = Switch->getParent();
- BasicBlock *NewDefaultBlock = SplitBlockPredecessors(
- Switch->getDefaultDest(), Switch->getParent(), "", DTU);
- auto *OrigDefaultBlock = Switch->getDefaultDest();
- Switch->setDefaultDest(&*NewDefaultBlock);
- if (DTU)
- DTU->applyUpdates({{DominatorTree::Insert, BB, &*NewDefaultBlock},
- {DominatorTree::Delete, BB, OrigDefaultBlock}});
- SplitBlock(&*NewDefaultBlock, &NewDefaultBlock->front(), DTU);
- SmallVector<DominatorTree::UpdateType, 2> Updates;
- if (DTU)
- for (auto *Successor : successors(NewDefaultBlock))
- Updates.push_back({DominatorTree::Delete, NewDefaultBlock, Successor});
- auto *NewTerminator = NewDefaultBlock->getTerminator();
- new UnreachableInst(Switch->getContext(), NewTerminator);
- EraseTerminatorAndDCECond(NewTerminator);
- if (DTU)
- DTU->applyUpdates(Updates);
-}
-
/// Turn a switch with two reachable destinations into an integer range
/// comparison and branch.
bool SimplifyCFGOpt::TurnSwitchRangeIntoICmp(SwitchInst *SI,
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll b/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
index 42b44143aea6..cbb6e2bfb246 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/basic.ll
@@ -382,7 +382,7 @@ 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 [[UNREACHABLE1:%.*]] [
; CHECK-NEXT: i32 1, label [[EXIT1:%.*]]
; CHECK-NEXT: i32 2, label [[EXIT2:%.*]]
; CHECK-NEXT: i32 3, label [[EXIT1]]
@@ -391,6 +391,10 @@ define i32 @switch_range(i32 %cond) {
; CHECK-NEXT: ret i32 1
; CHECK: exit2:
; CHECK-NEXT: ret i32 2
+; CHECK: unreachable1:
+; CHECK-NEXT: unreachable
+; CHECK: unreachable1.split:
+; CHECK-NEXT: br label [[UNREACHABLE:%.*]]
; CHECK: unreachable:
; CHECK-NEXT: ret i32 0
;
@@ -411,6 +415,38 @@ unreachable:
ret i32 0
}
+define i32 @switch_range_not_full(i32 %cond) {
+; CHECK-LABEL: @switch_range_not_full(
+; 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: i32 1, label [[EXIT1:%.*]]
+; CHECK-NEXT: i32 3, label [[EXIT2:%.*]]
+; CHECK-NEXT: ]
+; CHECK: exit1:
+; CHECK-NEXT: ret i32 1
+; CHECK: exit2:
+; CHECK-NEXT: ret i32 2
+; CHECK: unreachable:
+; CHECK-NEXT: ret i32 0
+;
+entry:
+ %s = urem i32 %cond, 3
+ %s1 = add i32 %s, 1
+ switch i32 %s1, label %unreachable [
+ i32 1, label %exit1
+ i32 3, label %exit2
+ ]
+
+exit1:
+ ret i32 1
+exit2:
+ ret i32 2
+unreachable:
+ ret i32 0
+}
+
define i1 @arg_attribute(i8* nonnull %a) {
; CHECK-LABEL: @arg_attribute(
; CHECK-NEXT: ret i1 false
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