Avoid generation of dead code in a few more situations.
- Emit variable declarations as "simple", we want to avoid forcing the creation
of a dummy basic block, but still need to make the variable available for
later use.
- With that, we can now skip IRgen for other unreachable statements (which
don't define a label).
- Anders, I added two fixmes on calls to EmitVLASize, can you check them?
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@76361 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGStmt.cpp b/lib/CodeGen/CGStmt.cpp
index 32477a3..0999947 100644
--- a/lib/CodeGen/CGStmt.cpp
+++ b/lib/CodeGen/CGStmt.cpp
@@ -43,13 +43,24 @@
if (EmitSimpleStmt(S))
return;
- // If we happen to be at an unreachable point just create a dummy
- // basic block to hold the code. We could change parts of irgen to
- // simply not generate this code, but this situation is rare and
- // probably not worth the effort.
- // FIXME: Verify previous performance/effort claim.
- EnsureInsertPoint();
-
+ // Check if we are generating unreachable code.
+ if (!HaveInsertPoint()) {
+ // If so, and the statement doesn't contain a label, then we do not need to
+ // generate actual code. This is safe because (1) the current point is
+ // unreachable, so we don't need to execute the code, and (2) we've already
+ // handled the statements which update internal data structures (like the
+ // local variable map) which could be used by subsequent statements.
+ if (!ContainsLabel(S)) {
+ // Verify that any decl statements were handled as simple, they may be in
+ // scope of subsequent reachable statements.
+ assert(!isa<DeclStmt>(*S) && "Unexpected DeclStmt!");
+ return;
+ }
+
+ // Otherwise, make a new block to hold the code.
+ EnsureInsertPoint();
+ }
+
// Generate a stoppoint if we are emitting debug info.
EmitStopPoint(S);
@@ -72,7 +83,6 @@
case Stmt::ForStmtClass: EmitForStmt(cast<ForStmt>(*S)); break;
case Stmt::ReturnStmtClass: EmitReturnStmt(cast<ReturnStmt>(*S)); break;
- case Stmt::DeclStmtClass: EmitDeclStmt(cast<DeclStmt>(*S)); break;
case Stmt::SwitchStmtClass: EmitSwitchStmt(cast<SwitchStmt>(*S)); break;
case Stmt::AsmStmtClass: EmitAsmStmt(cast<AsmStmt>(*S)); break;
@@ -103,6 +113,7 @@
default: return false;
case Stmt::NullStmtClass: break;
case Stmt::CompoundStmtClass: EmitCompoundStmt(cast<CompoundStmt>(*S)); break;
+ case Stmt::DeclStmtClass: EmitDeclStmt(cast<DeclStmt>(*S)); break;
case Stmt::LabelStmtClass: EmitLabelStmt(cast<LabelStmt>(*S)); break;
case Stmt::GotoStmtClass: EmitGotoStmt(cast<GotoStmt>(*S)); break;
case Stmt::BreakStmtClass: EmitBreakStmt(cast<BreakStmt>(*S)); break;