Code gen case statement ranges.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@42766 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CodeGen/CGStmt.cpp b/CodeGen/CGStmt.cpp
index c07929d..f9d614d 100644
--- a/CodeGen/CGStmt.cpp
+++ b/CodeGen/CGStmt.cpp
@@ -354,23 +354,73 @@
EmitBlock(new llvm::BasicBlock());
}
-void CodeGenFunction::EmitCaseStmt(const CaseStmt &S) {
- StartBlock("sw.bb");
- llvm::BasicBlock *CaseDest = Builder.GetInsertBlock();
- llvm::ConstantInt *LV = cast<llvm::ConstantInt>(EmitScalarExpr(S.getLHS()));
- SwitchInsn->addCase(LV, CaseDest);
- if (const Expr *R = S.getRHS()) {
- llvm::ConstantInt *RV = cast<llvm::ConstantInt>(EmitScalarExpr(R));
- llvm::APInt LHS = LV->getValue();
- llvm::APInt RHS = RV->getValue();
+/// EmitCaseStmtRange - If case statement range is not too big then
+/// add multiple cases to switch instruction, one for each value within
+/// the range. If range is too big then emit "if" condition check.
+void CodeGenFunction::EmitCaseStmtRange(const CaseStmt &S) {
+ assert (S.getRHS() && "Unexpected RHS value in CaseStmt");
+
+ const Expr *L = S.getLHS();
+ const Expr *R = S.getRHS();
+ llvm::ConstantInt *LV = cast<llvm::ConstantInt>(EmitScalarExpr(L));
+ llvm::ConstantInt *RV = cast<llvm::ConstantInt>(EmitScalarExpr(R));
+ llvm::APInt LHS = LV->getValue();
+ llvm::APInt RHS = RV->getValue();
+
+ llvm::APInt Range = RHS - LHS;
+ if (Range.ult(llvm::APInt(Range.getBitWidth(), 64))) {
+ // Range is small enough to add multiple switch instruction cases.
+ StartBlock("sw.bb");
+ llvm::BasicBlock *CaseDest = Builder.GetInsertBlock();
+ SwitchInsn->addCase(LV, CaseDest);
LHS++;
while (LHS != RHS) {
SwitchInsn->addCase(llvm::ConstantInt::get(LHS), CaseDest);
LHS++;
}
- SwitchInsn->addCase(llvm::ConstantInt::get(LHS), CaseDest);
- }
+ SwitchInsn->addCase(RV, CaseDest);
+ EmitStmt(S.getSubStmt());
+ return;
+ }
+
+ // The range is too big. Emit "if" condition.
+ llvm::BasicBlock *FalseDest = NULL;
+ llvm::BasicBlock *CaseDest = new llvm::BasicBlock("sw.bb");
+ // If we have already seen one case statement range for this switch
+ // instruction then piggy-back otherwise use default block as false
+ // destination.
+ if (CaseRangeBlock)
+ FalseDest = CaseRangeBlock;
+ else
+ FalseDest = SwitchInsn->getDefaultDest();
+
+ // Start new block to hold case statement range check instructions.
+ StartBlock("case.range");
+ CaseRangeBlock = Builder.GetInsertBlock();
+
+ // Emit range check.
+ llvm::Value *Diff =
+ Builder.CreateSub(SwitchInsn->getCondition(), LV, "tmp");
+ llvm::Value *Cond =
+ Builder.CreateICmpULE(Diff, llvm::ConstantInt::get(Range), "tmp");
+ Builder.CreateCondBr(Cond, CaseDest, FalseDest);
+
+ // Now emit case statement body.
+ EmitBlock(CaseDest);
+ EmitStmt(S.getSubStmt());
+}
+
+void CodeGenFunction::EmitCaseStmt(const CaseStmt &S) {
+ if (S.getRHS()) {
+ EmitCaseStmtRange(S);
+ return;
+ }
+
+ StartBlock("sw.bb");
+ llvm::BasicBlock *CaseDest = Builder.GetInsertBlock();
+ llvm::ConstantInt *LV = cast<llvm::ConstantInt>(EmitScalarExpr(S.getLHS()));
+ SwitchInsn->addCase(LV, CaseDest);
EmitStmt(S.getSubStmt());
}
@@ -386,6 +436,8 @@
// Handle nested switch statements.
llvm::SwitchInst *SavedSwitchInsn = SwitchInsn;
+ llvm::BasicBlock *SavedCRBlock = CaseRangeBlock;
+ CaseRangeBlock = NULL;
// Create basic block to hold stuff that comes after switch statement.
// Initially use it to hold DefaultStmt.
@@ -403,6 +455,12 @@
EmitStmt(S.getBody());
BreakContinueStack.pop_back();
+ // If one or more case statement range is seen then use CaseRangeBlock
+ // as the default block. False edge of CaseRangeBlock will lead to
+ // original default block.
+ if (CaseRangeBlock)
+ SwitchInsn->setSuccessor(0, CaseRangeBlock);
+
// Prune insert block if it is dummy.
llvm::BasicBlock *BB = Builder.GetInsertBlock();
if (isDummyBlock(BB))
@@ -411,4 +469,5 @@
// Place NextBlock as the new insert point.
Builder.SetInsertPoint(NextBlock);
SwitchInsn = SavedSwitchInsn;
+ CaseRangeBlock = SavedCRBlock;
}