r231508 - CodeGen: Emit constant temporaries into read-only globals.
Benjamin Kramer
benny.kra at googlemail.com
Fri Mar 6 12:00:03 PST 2015
Author: d0k
Date: Fri Mar 6 14:00:03 2015
New Revision: 231508
URL: http://llvm.org/viewvc/llvm-project?rev=231508&view=rev
Log:
CodeGen: Emit constant temporaries into read-only globals.
Instead of creating a copy on the stack just stash them in a private
constant global. This saves both the copying overhead and the stack
space, and gives the optimizer more room to constant fold.
This tries to make array temporaries more similar to regular arrays,
they can't use the same logic because a temporary has no VarDecl to be
bound to so we roll our own version here.
The original use case for this optimization was code like
for (int i : {1, 2, 3, 4, 5, 6, 7, 8, 10})
foo(i);
where without this patch (assuming that the loop is not unrolled) we
would alloca an array on the stack, copy the 10 values over and
iterate on that. With this patch we put the array in .text use it
directly. Apart from that case this helps on virtually any passing of
a constant std::initializer_list as a function argument.
Differential Revision: http://reviews.llvm.org/D8034
Modified:
cfe/trunk/lib/CodeGen/CGExpr.cpp
cfe/trunk/test/CodeGenCXX/compound-literals.cpp
cfe/trunk/test/CodeGenCXX/cxx0x-initializer-array.cpp
cfe/trunk/test/CodeGenCXX/cxx0x-initializer-references.cpp
cfe/trunk/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp
Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=231508&r1=231507&r2=231508&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGExpr.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExpr.cpp Fri Mar 6 14:00:03 2015
@@ -301,6 +301,25 @@ createReferenceTemporary(CodeGenFunction
switch (M->getStorageDuration()) {
case SD_FullExpression:
case SD_Automatic:
+ // If we have a constant temporary array or record try to promote it into a
+ // constant global under the same rules a normal constant would've been
+ // promoted. This is easier on the optimizer and generally emits fewer
+ // instructions.
+ if (CGF.CGM.getCodeGenOpts().MergeAllConstants &&
+ (M->getType()->isArrayType() || M->getType()->isRecordType()) &&
+ CGF.CGM.isTypeConstant(M->getType(), true))
+ if (llvm::Constant *Init =
+ CGF.CGM.EmitConstantExpr(Inner, M->getType(), &CGF)) {
+ auto *GV = new llvm::GlobalVariable(
+ CGF.CGM.getModule(), Init->getType(), /*isConstant=*/true,
+ llvm::GlobalValue::PrivateLinkage, Init, ".ref.tmp");
+ GV->setAlignment(
+ CGF.getContext().getTypeAlignInChars(M->getType()).getQuantity());
+ // Put the new global in the same COMDAT the function containing the
+ // temporary is in.
+ GV->setComdat(CGF.CurFn->getComdat());
+ return GV;
+ }
return CGF.CreateMemTemp(Inner->getType(), "ref.tmp");
case SD_Thread:
@@ -370,8 +389,9 @@ EmitMaterializeTemporaryExpr(const Mater
// Create and initialize the reference temporary.
llvm::Value *Object = createReferenceTemporary(*this, M, E);
if (auto *Var = dyn_cast<llvm::GlobalVariable>(Object)) {
- // If the temporary is a global and has a constant initializer, we may
- // have already initialized it.
+ // If the temporary is a global and has a constant initializer or is a
+ // constant temporary that we promoted to a global, we may have already
+ // initialized it.
if (!Var->hasInitializer()) {
Var->setInitializer(CGM.EmitNullConstant(E->getType()));
EmitAnyExprToMem(E, Object, Qualifiers(), /*IsInit*/true);
Modified: cfe/trunk/test/CodeGenCXX/compound-literals.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/compound-literals.cpp?rev=231508&r1=231507&r2=231508&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/compound-literals.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/compound-literals.cpp Fri Mar 6 14:00:03 2015
@@ -28,7 +28,7 @@ int f() {
// CHECK-LABEL: define i32 @_Z1gv()
int g() {
- // CHECK: store [2 x i32]* %{{[a-z0-9.]+}}, [2 x i32]** [[V:%[a-z0-9.]+]]
+ // CHECK: store [2 x i32]* @{{.*}}, [2 x i32]** [[V:%[a-z0-9.]+]]
const int (&v)[2] = (int [2]) {1,2};
// CHECK: [[A:%[a-z0-9.]+]] = load [2 x i32]*, [2 x i32]** [[V]]
Modified: cfe/trunk/test/CodeGenCXX/cxx0x-initializer-array.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/cxx0x-initializer-array.cpp?rev=231508&r1=231507&r2=231508&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/cxx0x-initializer-array.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/cxx0x-initializer-array.cpp Fri Mar 6 14:00:03 2015
@@ -42,10 +42,11 @@ namespace ValueInitArrayOfMemPtr {
// CHECK: call void @llvm.memcpy.p0i8.p0i8.i32(i8* %{{.*}}, i8* bitcast ([3 x i32]* @[[THREE_NULL_MEMPTRS]] to i8*), i32 12, i32 4, i1 false)
}
- // CHECK-LABEL: define void @_ZN22ValueInitArrayOfMemPtr1gEv
- void g() {
+ // Test dynamic initialization.
+ // CHECK-LABEL: define void @_ZN22ValueInitArrayOfMemPtr1gEMNS_1SEi
+ void g(p ptr) {
// CHECK: store i32 -1,
- f(a{});
+ f(a{ptr});
}
}
Modified: cfe/trunk/test/CodeGenCXX/cxx0x-initializer-references.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/cxx0x-initializer-references.cpp?rev=231508&r1=231507&r2=231508&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/cxx0x-initializer-references.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/cxx0x-initializer-references.cpp Fri Mar 6 14:00:03 2015
@@ -35,22 +35,30 @@ namespace reference {
// CHECK-NEXT: ret
}
- void reference_to_aggregate() {
+ void reference_to_aggregate(int i) {
// CHECK: getelementptr {{.*}}, i32 0, i32 0
// CHECK-NEXT: store i32 1
// CHECK-NEXT: getelementptr {{.*}}, i32 0, i32 1
- // CHECK-NEXT: store i32 2
+ // CHECK-NEXT: %[[I1:.*]] = load i32, i32*
+ // CHECK-NEXT: store i32 %[[I1]]
// CHECK-NEXT: store %{{.*}}* %{{.*}}, %{{.*}}** %{{.*}}, align
- const A &ra1{1, 2};
+ const A &ra1{1, i};
// CHECK-NEXT: getelementptr inbounds [3 x i32], [3 x i32]* %{{.*}}, i{{32|64}} 0, i{{32|64}} 0
// CHECK-NEXT: store i32 1
// CHECK-NEXT: getelementptr inbounds i32, i32* %{{.*}}, i{{32|64}} 1
// CHECK-NEXT: store i32 2
// CHECK-NEXT: getelementptr inbounds i32, i32* %{{.*}}, i{{32|64}} 1
- // CHECK-NEXT: store i32 3
+ // CHECK-NEXT: %[[I2:.*]] = load i32, i32*
+ // CHECK-NEXT: store i32 %[[I2]]
// CHECK-NEXT: store [3 x i32]* %{{.*}}, [3 x i32]** %{{.*}}, align
- const int (&arrayRef)[] = {1, 2, 3};
+ const int (&arrayRef)[] = {1, 2, i};
+
+ // CHECK: store %{{.*}}* @{{.*}}, %{{.*}}** %{{.*}}, align
+ const A &constra1{1, 2};
+
+ // CHECK-NEXT: store [3 x i32]* @{{.*}}, [3 x i32]** %{{.*}}, align
+ const int (&constarrayRef)[] = {1, 2, 3};
// CHECK-NEXT: ret
}
Modified: cfe/trunk/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp?rev=231508&r1=231507&r2=231508&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/cxx0x-initializer-stdinitializerlist.cpp Fri Mar 6 14:00:03 2015
@@ -72,6 +72,9 @@ namespace thread_local_global_array {
// CHECK: @[[PARTLY_CONSTANT_SECOND:_ZGRN15partly_constant2ilE.*]] = internal global [2 x i32] zeroinitializer, align 4
// CHECK: @[[PARTLY_CONSTANT_THIRD:_ZGRN15partly_constant2ilE.*]] = internal constant [4 x i32] [i32 5, i32 6, i32 7, i32 8], align 4
+// CHECK: @[[REFTMP1:.*]] = private constant [2 x i32] [i32 42, i32 43], comdat($_ZN7PR204451fILi0EEEvv), align 4
+// CHECK: @[[REFTMP2:.*]] = private constant [3 x %{{.*}}] [%{{.*}} { i32 1 }, %{{.*}} { i32 2 }, %{{.*}} { i32 3 }], align 4
+
// CHECK: appending global
@@ -215,17 +218,16 @@ void fn9() {
struct haslist1 {
std::initializer_list<int> il;
- haslist1();
+ haslist1(int i);
};
-// CHECK-LABEL: define void @_ZN8haslist1C2Ev
-haslist1::haslist1()
+// CHECK-LABEL: define void @_ZN8haslist1C2Ei
+haslist1::haslist1(int i)
// CHECK: alloca [3 x i32]
-// CHECK: store i32 1
+// CHECK: store i32 %
// CHECK: store i32 2
// CHECK: store i32 3
-// CHECK: store i{{32|64}} 3
- : il{1, 2, 3}
+ : il{i, 2, 3}
{
destroyme2 dm2;
}
@@ -244,16 +246,15 @@ haslist2::haslist2()
// CHECK: call void @_ZN10destroyme1D1Ev
}
-void fn10() {
- // CHECK-LABEL: define void @_Z4fn10v
+void fn10(int i) {
+ // CHECK-LABEL: define void @_Z4fn10i
// CHECK: alloca [3 x i32]
// CHECK: call noalias i8* @_Znw{{[jm]}}
- // CHECK: store i32 1
+ // CHECK: store i32 %
// CHECK: store i32 2
// CHECK: store i32 3
// CHECK: store i32*
- // CHECK: store i{{32|64}} 3
- (void) new std::initializer_list<int> {1, 2, 3};
+ (void) new std::initializer_list<int> {i, 2, 3};
}
void fn11() {
@@ -462,6 +463,22 @@ namespace PR20445 {
template<int x> void f() { new MyClass({42, 43}); }
template void f<0>();
// CHECK-LABEL: define {{.*}} @_ZN7PR204451fILi0EEEvv(
+ // CHECK: store i32* getelementptr inbounds ([2 x i32]* @[[REFTMP1]], i64 0, i64 0)
// CHECK: call void @_ZN7PR204456vectorC1ESt16initializer_listIiE(
// CHECK: call void @_ZN7PR204457MyClassC1ERKNS_6vectorE(
}
+
+namespace ConstExpr {
+ class C {
+ int x;
+ public:
+ constexpr C(int x) : x(x) {}
+ };
+ void f(std::initializer_list<C>);
+ void g() {
+// CHECK-LABEL: _ZN9ConstExpr1gEv
+// CHECK: store %"class.ConstExpr::C"* getelementptr inbounds ([3 x %"class.ConstExpr::C"]* @[[REFTMP2]], i64 0, i64 0)
+// CHECK: call void @_ZN9ConstExpr1fESt16initializer_listINS_1CEE
+ f({C(1), C(2), C(3)});
+ }
+}
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