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Differential D64386

CodeGen: Use memset in initializers for non-zeros
AbandonedPublic

Authored by vitalybuka on Jul 8 2019, 10:08 PM.

Details

Reviewers
eugenis
pcc
jfb
efriedma
hfinkel

Diff Detail

Event Timeline

vitalybuka created this revision.Jul 8 2019, 10:08 PM
Herald added a project: Restricted Project. · View Herald TranscriptJul 8 2019, 10:08 PM
Herald added subscribers: cfe-commits, dexonsmith. · View Herald Transcript
Harbormaster completed remote builds in B34564: Diff 208596.Jul 8 2019, 10:08 PM
vitalybuka added a parent revision: D64382: Use getMostFrequentByte to decide if should used memset+stores.Jul 8 2019, 10:08 PM
vitalybuka added a child revision: D64387: CodeGen: Do not memset if following stores will overwrite entire variable.Jul 8 2019, 10:57 PM
xbolva00 added reviewers: efriedma, hfinkel.Jul 24 2019, 7:50 AM
hfinkel added inline comments.Jul 24 2019, 9:00 AM
clang/test/CodeGen/init-memset.c
29

I'd be more comfortable if the test here actually checked the length and the value in the memset call here and below.

vitalybuka abandoned this revision.Jun 16 2021, 3:18 PM

Revision Contents

PathSize
clang/
lib/
CodeGen/
5 lines
test/
CodeGen/
5 lines

Diff 208596

clang/lib/CodeGen/CGDecl.cpp

Show First 20 Lines • Show All 967 Lines • ▼ Show 20 Lines if (0) {
} }
} }
// TODO: Tweak these constants or use "density". // TODO: Tweak these constants or use "density".
uint64_t SizeLimit = 32; uint64_t SizeLimit = 32;
if (GlobalSize <= SizeLimit) if (GlobalSize <= SizeLimit)
return nullptr; return nullptr;
// TODO: Remove. It's here just to keep behavior.
if (MFB.Other && MFB.Value &&
MFB.Value != llvm::ConstantInt::get(CGM.Int8Ty, 0))
return nullptr;
if (!MFB.Value) { if (!MFB.Value) {
// We don't know most frequent byte, we may still completely initialize it // We don't know most frequent byte, we may still completely initialize it
// with small number of stores. // with small number of stores.
// TODO: Use llvm::UndefValue::get. If we get here and later we decide // TODO: Use llvm::UndefValue::get. If we get here and later we decide
// that number of stores is small enough to use memset+store then store are // that number of stores is small enough to use memset+store then store are
// going to replace entire bzeroed range. With UndefValue we can skip that // going to replace entire bzeroed range. With UndefValue we can skip that
// bogus memset. I will do that as a separate patch. // bogus memset. I will do that as a separate patch.
MFB.Value = llvm::ConstantInt::get(CGM.Int8Ty, 0); MFB.Value = llvm::ConstantInt::get(CGM.Int8Ty, 0);
▲ Show 20 Lines • Show All 1,553 Lines • Show Last 20 Lines

clang/test/CodeGen/init-memset.c

Show All 20 Linesvoid test_all_zeros() {
int a[16] = {}; int a[16] = {};
// CHECK: call void @llvm.memset.{{.*}} // CHECK: call void @llvm.memset.{{.*}}
use(a); use(a);
} }
void test_all_a() { void test_all_a() {
// CHECK-LABEL: define void @test_all_a() // CHECK-LABEL: define void @test_all_a()
char a[] = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"; char a[] = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
// CHECK: call void @llvm.memcpy.{{.*}} // CHECK: call void @llvm.memset.{{.*}}
hfinkelUnsubmitted
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I'd be more comfortable if the test here actually checked the length and the value in the memset call here and below.

hfinkel: I'd be more comfortable if the test here actually checked the length and the value in the…
use(a); use(a);
} }
void test_most_zeros() { void test_most_zeros() {
// CHECK-LABEL: define void @test_most_zeros() // CHECK-LABEL: define void @test_most_zeros()
int a[16] = {0, 0, 1}; int a[16] = {0, 0, 1};
// CHECK: call void @llvm.memset.{{.*}} // CHECK: call void @llvm.memset.{{.*}}
// CHECK: store i32 1 // CHECK: store i32 1
use(a); use(a);
} }
void test_most_a() { void test_most_a() {
// CHECK-LABEL: define void @test_most_a() // CHECK-LABEL: define void @test_most_a()
char a[] = "aaaaazaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"; char a[] = "aaaaazaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
// CHECK: call void @llvm.memcpy.{{.*}} // CHECK: call void @llvm.memset.{{.*}}
// CHECK: store i8 122
use(a); use(a);
} }