[MC] Relax .fill size requirements
Avoid requirement that number of values must be known at assembler
time.
Fixes PR33586.
Reviewers: rnk, peter.smith, echristo, jyknight
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D46703
llvm-svn: 332741
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index a8a0177..bde838a 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -295,10 +295,13 @@
return cast<MCCompactEncodedInstFragment>(F).getContents().size();
case MCFragment::FT_Fill: {
auto &FF = cast<MCFillFragment>(F);
- int64_t Size = 0;
- if (!FF.getSize().evaluateAsAbsolute(Size, Layout))
+ int64_t NumValues = 0;
+ if (!FF.getNumValues().evaluateAsAbsolute(NumValues, Layout)) {
getContext().reportError(FF.getLoc(),
"expected assembly-time absolute expression");
+ return 0;
+ }
+ int64_t Size = NumValues * FF.getValueSize();
if (Size < 0) {
getContext().reportError(FF.getLoc(), "invalid number of bytes");
return 0;
@@ -557,19 +560,35 @@
case MCFragment::FT_Fill: {
++stats::EmittedFillFragments;
const MCFillFragment &FF = cast<MCFillFragment>(F);
- uint8_t V = FF.getValue();
+ uint64_t V = FF.getValue();
+ unsigned VSize = FF.getValueSize();
const unsigned MaxChunkSize = 16;
char Data[MaxChunkSize];
- memcpy(Data, &V, 1);
- for (unsigned I = 1; I < MaxChunkSize; ++I)
- Data[I] = Data[0];
+ // Duplicate V into Data as byte vector to reduce number of
+ // writes done. As such, do endian conversion here, not in OW.
+ const bool isLittleEndian = Asm.getContext().getAsmInfo()->isLittleEndian();
+ for (unsigned I = 0; I != VSize; ++I) {
+ unsigned index = isLittleEndian ? I : (VSize - I - 1);
+ Data[I] = uint8_t(V >> (index * 8));
+ }
+ for (unsigned I = VSize; I < MaxChunkSize; ++I)
+ Data[I] = Data[I - VSize];
- uint64_t Size = FragmentSize;
- for (unsigned ChunkSize = MaxChunkSize; ChunkSize; ChunkSize /= 2) {
- StringRef Ref(Data, ChunkSize);
- for (uint64_t I = 0, E = Size / ChunkSize; I != E; ++I)
- OW->writeBytes(Ref);
- Size = Size % ChunkSize;
+ // Set to largest multiple of VSize in Data.
+ const unsigned NumPerChunk = MaxChunkSize / VSize;
+ // Set ChunkSize to largest multiple of VSize in Data
+ const unsigned ChunkSize = VSize * NumPerChunk;
+
+ // Do copies by chunk.
+ StringRef Ref(Data, ChunkSize);
+ for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I)
+ OW->writeBytes(Ref);
+
+ // do remainder if needed.
+ unsigned TrailingCount = FragmentSize % ChunkSize;
+ if (TrailingCount) {
+ StringRef RefTail(Data, TrailingCount);
+ OW->writeBytes(RefTail);
}
break;
}
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index e7775ca..2d6b83e 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -388,7 +388,8 @@
case MCFragment::FT_Fill: {
const MCFillFragment *FF = cast<MCFillFragment>(this);
OS << " Value:" << static_cast<unsigned>(FF->getValue())
- << " Size:" << FF->getSize();
+ << " ValueSize:" << static_cast<unsigned>(FF->getValueSize())
+ << " NumValues:" << FF->getNumValues();
break;
}
case MCFragment::FT_Relaxable: {
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index b2008b3..22b9743 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -637,31 +637,37 @@
flushPendingLabels(DF, DF->getContents().size());
assert(getCurrentSectionOnly() && "need a section");
- insert(new MCFillFragment(FillValue, NumBytes, Loc));
+ insert(new MCFillFragment(FillValue, 1, NumBytes, Loc));
}
void MCObjectStreamer::emitFill(const MCExpr &NumValues, int64_t Size,
int64_t Expr, SMLoc Loc) {
int64_t IntNumValues;
- if (!NumValues.evaluateAsAbsolute(IntNumValues, getAssemblerPtr())) {
- getContext().reportError(Loc, "expected absolute expression");
+ // Do additional checking now if we can resolve the value.
+ if (NumValues.evaluateAsAbsolute(IntNumValues, getAssemblerPtr())) {
+ if (IntNumValues < 0) {
+ getContext().getSourceManager()->PrintMessage(
+ Loc, SourceMgr::DK_Warning,
+ "'.fill' directive with negative repeat count has no effect");
+ return;
+ }
+ // Emit now if we can for better errors.
+ int64_t NonZeroSize = Size > 4 ? 4 : Size;
+ Expr &= ~0ULL >> (64 - NonZeroSize * 8);
+ for (uint64_t i = 0, e = IntNumValues; i != e; ++i) {
+ EmitIntValue(Expr, NonZeroSize);
+ if (NonZeroSize < Size)
+ EmitIntValue(0, Size - NonZeroSize);
+ }
return;
}
- if (IntNumValues < 0) {
- getContext().getSourceManager()->PrintMessage(
- Loc, SourceMgr::DK_Warning,
- "'.fill' directive with negative repeat count has no effect");
- return;
- }
+ // Otherwise emit as fragment.
+ MCDataFragment *DF = getOrCreateDataFragment();
+ flushPendingLabels(DF, DF->getContents().size());
- int64_t NonZeroSize = Size > 4 ? 4 : Size;
- Expr &= ~0ULL >> (64 - NonZeroSize * 8);
- for (uint64_t i = 0, e = IntNumValues; i != e; ++i) {
- EmitIntValue(Expr, NonZeroSize);
- if (NonZeroSize < Size)
- EmitIntValue(0, Size - NonZeroSize);
- }
+ assert(getCurrentSectionOnly() && "need a section");
+ insert(new MCFillFragment(Expr, Size, NumValues, Loc));
}
void MCObjectStreamer::EmitFileDirective(StringRef Filename) {
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 0696d6f..22e05c1 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -630,10 +630,11 @@
Align->getMaxBytesToEmit());
DataBytes.resize(Size, Value);
} else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) {
- int64_t Size;
- if (!Fill->getSize().evaluateAsAbsolute(Size))
+ int64_t NumValues;
+ if (!Fill->getNumValues().evaluateAsAbsolute(NumValues))
llvm_unreachable("The fill should be an assembler constant");
- DataBytes.insert(DataBytes.end(), Size, Fill->getValue());
+ DataBytes.insert(DataBytes.end(), Fill->getValueSize() * NumValues,
+ Fill->getValue());
} else {
const auto &DataFrag = cast<MCDataFragment>(Frag);
const SmallVectorImpl<char> &Contents = DataFrag.getContents();