[PATCH] D42549: [CodeGen] Use the zero initializer instead of storing an all zero representation.
Matt Davis via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Fri Feb 9 14:12:01 PST 2018
This revision was automatically updated to reflect the committed changes.
Closed by commit rC324776: [CodeGen] Use the zero initializer instead of storing an all zero… (authored by mattd, committed by ).
Repository:
rC Clang
https://reviews.llvm.org/D42549
Files:
lib/CodeGen/CGExprConstant.cpp
test/CodeGen/array-init.c
Index: test/CodeGen/array-init.c
===================================================================
--- test/CodeGen/array-init.c
+++ test/CodeGen/array-init.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 %s -O0 -triple x86_64-unknown-linux-gnu -emit-llvm -o - | FileCheck %s
+
+// CHECK: @{{.*}}.a1 = internal constant [5 x i32] [i32 0, i32 1, i32 2, i32 0, i32 0]
+// CHECK: @{{.*}}.a2 = internal constant [5 x i32] zeroinitializer
+// CHECK: @{{.*}}.a3 = internal constant [5 x i32] zeroinitializer
+
+void testConstArrayInits(void)
+{
+ const int a1[5] = {0,1,2};
+ const int a2[5] = {0,0,0};
+ const int a3[5] = {0};
+}
Index: lib/CodeGen/CGExprConstant.cpp
===================================================================
--- lib/CodeGen/CGExprConstant.cpp
+++ lib/CodeGen/CGExprConstant.cpp
@@ -859,25 +859,33 @@
// Copy initializer elements.
SmallVector<llvm::Constant*, 16> Elts;
- Elts.reserve(NumInitableElts + NumElements);
+ Elts.reserve(std::max(NumInitableElts, NumElements));
bool RewriteType = false;
+ bool AllNullValues = true;
for (unsigned i = 0; i < NumInitableElts; ++i) {
Expr *Init = ILE->getInit(i);
llvm::Constant *C = Emitter.tryEmitPrivateForMemory(Init, EltType);
if (!C)
return nullptr;
RewriteType |= (C->getType() != ElemTy);
Elts.push_back(C);
+ if (AllNullValues && !C->isNullValue())
+ AllNullValues = false;
}
+ // If all initializer elements are "zero," then avoid storing NumElements
+ // instances of the zero representation.
+ if (AllNullValues)
+ return llvm::ConstantAggregateZero::get(AType);
+
RewriteType |= (fillC->getType() != ElemTy);
Elts.resize(NumElements, fillC);
if (RewriteType) {
// FIXME: Try to avoid packing the array
std::vector<llvm::Type*> Types;
- Types.reserve(NumInitableElts + NumElements);
+ Types.reserve(Elts.size());
for (unsigned i = 0, e = Elts.size(); i < e; ++i)
Types.push_back(Elts[i]->getType());
llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
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