Variable auto-init: split out small arrays
Summary: Following up with r355181, initialize small arrays as well.
LLVM stage2 shows a tiny size gain.
<rdar://48523005>
Reviewers: glider, pcc, kcc, rjmccall
Subscribers: jkorous, dexonsmith, jdoerfert, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D58885
llvm-svn: 355660
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 4acfb15..c09077bb 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -970,12 +970,12 @@
return llvm::isBytewiseValue(Init);
}
-/// Decide whether we want to split a constant structure store into a sequence
-/// of its fields' stores. This may cost us code size and compilation speed,
-/// but plays better with store optimizations.
-static bool shouldSplitStructStore(CodeGenModule &CGM,
- uint64_t GlobalByteSize) {
- // Don't break structures that occupy more than one cacheline.
+/// Decide whether we want to split a constant structure or array store into a
+/// sequence of its fields' stores. This may cost us code size and compilation
+/// speed, but plays better with store optimizations.
+static bool shouldSplitConstantStore(CodeGenModule &CGM,
+ uint64_t GlobalByteSize) {
+ // Don't break things that occupy more than one cacheline.
uint64_t ByteSizeLimit = 64;
if (CGM.getCodeGenOpts().OptimizationLevel == 0)
return false;
@@ -1203,9 +1203,9 @@
CGBuilderTy &Builder,
llvm::Constant *constant) {
auto *Ty = constant->getType();
- bool isScalar = Ty->isIntOrIntVectorTy() || Ty->isPtrOrPtrVectorTy() ||
- Ty->isFPOrFPVectorTy();
- if (isScalar) {
+ bool canDoSingleStore = Ty->isIntOrIntVectorTy() ||
+ Ty->isPtrOrPtrVectorTy() || Ty->isFPOrFPVectorTy();
+ if (canDoSingleStore) {
Builder.CreateStore(constant, Loc, isVolatile);
return;
}
@@ -1213,12 +1213,13 @@
auto *Int8Ty = llvm::IntegerType::getInt8Ty(CGM.getLLVMContext());
auto *IntPtrTy = CGM.getDataLayout().getIntPtrType(CGM.getLLVMContext());
- // If the initializer is all or mostly the same, codegen with bzero / memset
- // then do a few stores afterward.
uint64_t ConstantSize = CGM.getDataLayout().getTypeAllocSize(Ty);
if (!ConstantSize)
return;
auto *SizeVal = llvm::ConstantInt::get(IntPtrTy, ConstantSize);
+
+ // If the initializer is all or mostly the same, codegen with bzero / memset
+ // then do a few stores afterward.
if (shouldUseBZeroPlusStoresToInitialize(constant, ConstantSize)) {
Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, 0), SizeVal,
isVolatile);
@@ -1232,6 +1233,7 @@
return;
}
+ // If the initializer is a repeated byte pattern, use memset.
llvm::Value *Pattern = shouldUseMemSetToInitialize(constant, ConstantSize);
if (Pattern) {
uint64_t Value = 0x00;
@@ -1245,20 +1247,34 @@
return;
}
- llvm::StructType *STy = dyn_cast<llvm::StructType>(Ty);
- // FIXME: handle the case when STy != Loc.getElementType().
- // FIXME: handle non-struct aggregate types.
- if (STy && (STy == Loc.getElementType()) &&
- shouldSplitStructStore(CGM, ConstantSize)) {
- for (unsigned i = 0; i != constant->getNumOperands(); i++) {
- Address EltPtr = Builder.CreateStructGEP(Loc, i);
- emitStoresForConstant(
- CGM, D, EltPtr, isVolatile, Builder,
- cast<llvm::Constant>(Builder.CreateExtractValue(constant, i)));
+ // If the initializer is small, use a handful of stores.
+ if (shouldSplitConstantStore(CGM, ConstantSize)) {
+ if (auto *STy = dyn_cast<llvm::StructType>(Ty)) {
+ // FIXME: handle the case when STy != Loc.getElementType().
+ if (STy == Loc.getElementType()) {
+ for (unsigned i = 0; i != constant->getNumOperands(); i++) {
+ Address EltPtr = Builder.CreateStructGEP(Loc, i);
+ emitStoresForConstant(
+ CGM, D, EltPtr, isVolatile, Builder,
+ cast<llvm::Constant>(Builder.CreateExtractValue(constant, i)));
+ }
+ return;
+ }
+ } else if (auto *ATy = dyn_cast<llvm::ArrayType>(Ty)) {
+ // FIXME: handle the case when ATy != Loc.getElementType().
+ if (ATy == Loc.getElementType()) {
+ for (unsigned i = 0; i != ATy->getNumElements(); i++) {
+ Address EltPtr = Builder.CreateConstArrayGEP(Loc, i);
+ emitStoresForConstant(
+ CGM, D, EltPtr, isVolatile, Builder,
+ cast<llvm::Constant>(Builder.CreateExtractValue(constant, i)));
+ }
+ return;
+ }
}
- return;
}
+ // Copy from a global.
Builder.CreateMemCpy(
Loc,
createUnnamedGlobalFrom(CGM, D, Builder, constant, Loc.getAlignment()),