Compress Repeated Byte Output
Emit a repeated sequence of bytes using .zero. This saves an enormous
amount of asm file space for certain programs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138864 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 12c5684..e888985 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -44,6 +44,7 @@
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
+#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Timer.h"
using namespace llvm;
@@ -1520,12 +1521,67 @@
static void EmitGlobalConstantImpl(const Constant *C, unsigned AddrSpace,
AsmPrinter &AP);
+/// isRepeatedByteSequence - Determine whether the given value is
+/// composed of a repeated sequence of identical bytes and return the
+/// byte value. If it is not a repeated sequence, return -1.
+static int isRepeatedByteSequence(const Value *V, TargetMachine &TM) {
+
+ if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
+ if (CI->getBitWidth() > 64) return -1;
+
+ uint64_t Size = TM.getTargetData()->getTypeAllocSize(V->getType());
+ uint64_t Value = CI->getZExtValue();
+
+ // Make sure the constant is at least 8 bits long and has a power
+ // of 2 bit width. This guarantees the constant bit width is
+ // always a multiple of 8 bits, avoiding issues with padding out
+ // to Size and other such corner cases.
+ if (CI->getBitWidth() < 8 || !isPowerOf2_64(CI->getBitWidth())) return -1;
+
+ uint8_t Byte = static_cast<uint8_t>(Value);
+
+ for (unsigned i = 1; i < Size; ++i) {
+ Value >>= 8;
+ if (static_cast<uint8_t>(Value) != Byte) return -1;
+ }
+ return Byte;
+ }
+ if (const ConstantArray *CA = dyn_cast<ConstantArray>(V)) {
+ // Make sure all array elements are sequences of the same repeated
+ // byte.
+ if (CA->getNumOperands() == 0) return -1;
+
+ int Byte = isRepeatedByteSequence(CA->getOperand(0), TM);
+ if (Byte == -1) return -1;
+
+ for (unsigned i = 1, e = CA->getNumOperands(); i != e; ++i) {
+ int ThisByte = isRepeatedByteSequence(CA->getOperand(i), TM);
+ if (ThisByte == -1) return -1;
+ if (Byte != ThisByte) return -1;
+ }
+ return Byte;
+ }
+
+ return -1;
+}
+
static void EmitGlobalConstantArray(const ConstantArray *CA, unsigned AddrSpace,
AsmPrinter &AP) {
if (AddrSpace != 0 || !CA->isString()) {
- // Not a string. Print the values in successive locations
- for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
- EmitGlobalConstantImpl(CA->getOperand(i), AddrSpace, AP);
+ // Not a string. Print the values in successive locations.
+
+ // See if we can aggregate some values. Make sure it can be
+ // represented as a series of bytes of the constant value.
+ int Value = isRepeatedByteSequence(CA, AP.TM);
+
+ if (Value != -1) {
+ unsigned Bytes = AP.TM.getTargetData()->getTypeAllocSize(CA->getType());
+ AP.OutStreamer.EmitFill(Bytes, Value, AddrSpace);
+ }
+ else {
+ for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
+ EmitGlobalConstantImpl(CA->getOperand(i), AddrSpace, AP);
+ }
return;
}
diff --git a/test/CodeGen/X86/2011-08-29-BlockConstant.ll b/test/CodeGen/X86/2011-08-29-BlockConstant.ll
new file mode 100644
index 0000000..83e4bcc
--- /dev/null
+++ b/test/CodeGen/X86/2011-08-29-BlockConstant.ll
@@ -0,0 +1,34 @@
+; RUN: llc -march=x86-64 < %s | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-unknown-linux-gnu"
+
+@x = global [500 x i64] zeroinitializer, align 64 ; <[500 x i64]*>
+; CHECK: x:
+; CHECK: .zero 4000
+
+@y = global [63 x i64] [
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262,
+ i64 6799976246779207262, i64 6799976246779207262, i64 6799976246779207262],
+ align 64 ; <[63 x i64]*> 0x5e5e5e5e
+; CHECK: y:
+; CHECK: .zero 504,94
