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Compress Repeated Byte Output

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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
This commit is contained in:
David Greene 2011-08-31 17:30:56 +00:00
parent 0f3abd8d68
commit d92e2e4f88
2 changed files with 93 additions and 3 deletions
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62
lib/CodeGen/AsmPrinter/AsmPrinter.cpp
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@ -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 const MCExpr *LowerConstant(const Constant *CV, AsmPrinter &AP) {
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;
}

34
test/CodeGen/X86/2011-08-29-BlockConstant.ll Normal file
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@ -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