[cfe-commits] r76361 - in /cfe/trunk: lib/CodeGen/CGDecl.cpp lib/CodeGen/CGStmt.cpp lib/CodeGen/CodeGenFunction.cpp lib/CodeGen/CodeGenFunction.h test/CodeGen/unreachable.c
Daniel Dunbar
daniel at zuster.org
Sat Jul 18 23:58:08 PDT 2009
Author: ddunbar
Date: Sun Jul 19 01:58:07 2009
New Revision: 76361
URL: http://llvm.org/viewvc/llvm-project?rev=76361&view=rev
Log:
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?
Added:
cfe/trunk/test/CodeGen/unreachable.c
Modified:
cfe/trunk/lib/CodeGen/CGDecl.cpp
cfe/trunk/lib/CodeGen/CGStmt.cpp
cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
cfe/trunk/lib/CodeGen/CodeGenFunction.h
Modified: cfe/trunk/lib/CodeGen/CGDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGDecl.cpp?rev=76361&r1=76360&r2=76361&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGDecl.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGDecl.cpp Sun Jul 19 01:58:07 2009
@@ -112,7 +112,6 @@
}
void CodeGenFunction::EmitStaticBlockVarDecl(const VarDecl &D) {
-
llvm::Value *&DMEntry = LocalDeclMap[&D];
assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
@@ -124,6 +123,8 @@
DMEntry = GV;
// Make sure to evaluate VLA bounds now so that we have them for later.
+ //
+ // FIXME: Can this happen?
if (D.getType()->isVariablyModifiedType())
EmitVLASize(D.getType());
@@ -274,9 +275,12 @@
::InternalLinkage);
}
+ // FIXME: Can this happen?
if (Ty->isVariablyModifiedType())
EmitVLASize(Ty);
} else {
+ EnsureInsertPoint();
+
if (!DidCallStackSave) {
// Save the stack.
const llvm::Type *LTy =
@@ -321,6 +325,11 @@
// Emit debug info for local var declaration.
if (CGDebugInfo *DI = getDebugInfo()) {
+ // FIXME: Remove this once debug info isn't modeled as instructions.
+ EnsureInsertPoint();
+
+ EmitStopPoint(S);
+
DI->setLocation(D.getLocation());
if (Target.useGlobalsForAutomaticVariables()) {
DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D);
@@ -338,7 +347,18 @@
}
// If this local has an initializer, emit it now.
- if (const Expr *Init = D.getInit()) {
+ const Expr *Init = D.getInit();
+
+ // If we are at an unreachable point, we don't need to emit the initializer
+ // unless it contains a label.
+ if (!HaveInsertPoint()) {
+ if (!ContainsLabel(Init))
+ Init = 0;
+ else
+ EnsureInsertPoint();
+ }
+
+ if (Init) {
llvm::Value *Loc = DeclPtr;
if (isByRef) {
bool needsCopyDispose = BlockRequiresCopying(Ty);
@@ -357,10 +377,12 @@
EmitAggExpr(Init, Loc, D.getType().isVolatileQualified());
}
}
+
if (isByRef) {
const llvm::PointerType *PtrToInt8Ty
= VMContext.getPointerTypeUnqual(llvm::Type::Int8Ty);
+ EnsureInsertPoint();
llvm::Value *isa_field = Builder.CreateStructGEP(DeclPtr, 0);
llvm::Value *forwarding_field = Builder.CreateStructGEP(DeclPtr, 1);
llvm::Value *flags_field = Builder.CreateStructGEP(DeclPtr, 2);
Modified: cfe/trunk/lib/CodeGen/CGStmt.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGStmt.cpp?rev=76361&r1=76360&r2=76361&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGStmt.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGStmt.cpp Sun Jul 19 01:58:07 2009
@@ -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;
Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.cpp?rev=76361&r1=76360&r2=76361&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.cpp Sun Jul 19 01:58:07 2009
@@ -450,19 +450,19 @@
}
}
-llvm::Value *CodeGenFunction::GetVLASize(const VariableArrayType *VAT)
-{
+llvm::Value *CodeGenFunction::GetVLASize(const VariableArrayType *VAT) {
llvm::Value *&SizeEntry = VLASizeMap[VAT];
assert(SizeEntry && "Did not emit size for type");
return SizeEntry;
}
-llvm::Value *CodeGenFunction::EmitVLASize(QualType Ty)
-{
+llvm::Value *CodeGenFunction::EmitVLASize(QualType Ty) {
assert(Ty->isVariablyModifiedType() &&
"Must pass variably modified type to EmitVLASizes!");
+ EnsureInsertPoint();
+
if (const VariableArrayType *VAT = getContext().getAsVariableArrayType(Ty)) {
llvm::Value *&SizeEntry = VLASizeMap[VAT];
Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=76361&r1=76360&r2=76361&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Sun Jul 19 01:58:07 2009
@@ -147,7 +147,11 @@
~CleanupScope() {
CGF.PushCleanupBlock(CleanupBB);
- CGF.Builder.SetInsertPoint(CurBB);
+ // FIXME: This is silly, move this into the builder.
+ if (CurBB)
+ CGF.Builder.SetInsertPoint(CurBB);
+ else
+ CGF.Builder.ClearInsertionPoint();
}
};
@@ -510,6 +514,8 @@
// EmitVLASize - Generate code for any VLA size expressions that might occur
// in a variably modified type. If Ty is a VLA, will return the value that
// corresponds to the size in bytes of the VLA type. Will return 0 otherwise.
+ ///
+ /// This function can be called with a null (unreachable) insert point.
llvm::Value *EmitVLASize(QualType Ty);
// GetVLASize - Returns an LLVM value that corresponds to the size in bytes
@@ -537,9 +543,21 @@
// Declaration Emission
//===--------------------------------------------------------------------===//
+ /// EmitDecl - Emit a declaration.
+ ///
+ /// This function can be called with a null (unreachable) insert point.
void EmitDecl(const Decl &D);
+
+ /// EmitBlockVarDecl - Emit a block variable declaration.
+ ///
+ /// This function can be called with a null (unreachable) insert point.
void EmitBlockVarDecl(const VarDecl &D);
+
+ /// EmitLocalBlockVarDecl - Emit a local block variable declaration.
+ ///
+ /// This function can be called with a null (unreachable) insert point.
void EmitLocalBlockVarDecl(const VarDecl &D);
+
void EmitStaticBlockVarDecl(const VarDecl &D);
/// EmitParmDecl - Emit a ParmVarDecl or an ImplicitParamDecl.
Added: cfe/trunk/test/CodeGen/unreachable.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/unreachable.c?rev=76361&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/unreachable.c (added)
+++ cfe/trunk/test/CodeGen/unreachable.c Sun Jul 19 01:58:07 2009
@@ -0,0 +1,26 @@
+// RUN: clang-cc -emit-llvm -o %t %s &&
+// RUN: grep '@unreachable' %t | count 0
+
+extern int unreachable();
+
+int f0() {
+ return 0;
+ unreachable();
+}
+
+int f1(int i) {
+ goto L0;
+ int a = unreachable();
+ L0:
+ return 0;
+}
+
+int f2(int i) {
+ goto L0;
+ unreachable();
+ int a;
+ unreachable();
+ L0:
+ a = i + 1;
+ return a;
+}
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