68 lines
2.7 KiB
Text
68 lines
2.7 KiB
Text
- Use int3 trap padding between functions instead of trapsleds with a leading jump.
|
|
- Emit trap alignment between basic blocks that are unreachable via
|
|
fallthrough. Avoids unnecessary jmp instructions in the middle
|
|
of functions and makes disassembly nicer to read.
|
|
|
|
Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
|
|
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp.orig
|
|
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
|
|
@@ -745,7 +745,7 @@ void AsmPrinter::emitFunctionHeader() {
|
|
|
|
emitLinkage(&F, CurrentFnSym);
|
|
if (MAI->hasFunctionAlignment())
|
|
- emitAlignment(MF->getAlignment(), &F);
|
|
+ emitTrapAlignment(MF->getAlignment(), &F);
|
|
|
|
if (MAI->hasDotTypeDotSizeDirective())
|
|
OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_ELF_TypeFunction);
|
|
@@ -2462,6 +2462,30 @@ void AsmPrinter::emitAlignment(Align Alignment, const
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
+/// emitTrapAlignment - Emit an alignment directive to the specified power of
|
|
+/// two boundary, but call emitTrapToAlignment to fill with Trap instructions
|
|
+/// if the Target implements emitTrapToAlignment.
|
|
+void AsmPrinter::emitTrapAlignment(Align Alignment, const GlobalObject *GV) const {
|
|
+ if (GV)
|
|
+ Alignment = getGVAlignment(GV, GV->getParent()->getDataLayout(), Alignment);
|
|
+
|
|
+ if (Alignment == Align(1)) return; // 1-byte aligned: no need to emit alignment.
|
|
+
|
|
+ emitTrapToAlignment(Alignment);
|
|
+}
|
|
+
|
|
+//===----------------------------------------------------------------------===//
|
|
+/// emitTrapToAlignment - Emit an alignment directive to the specified power
|
|
+/// of two boundary. This default implementation calls EmitCodeAlignment on
|
|
+/// the OutStreamer, but can be overridden by Target implementations.
|
|
+void AsmPrinter::emitTrapToAlignment(Align Alignment) const {
|
|
+ if (Alignment == Align(1)) return;
|
|
+ OutStreamer->emitCodeAlignment(Alignment.value());
|
|
+}
|
|
+
|
|
+
|
|
+
|
|
+//===----------------------------------------------------------------------===//
|
|
// Constant emission.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
@@ -3246,10 +3270,17 @@ void AsmPrinter::emitBasicBlockStart(const MachineBasi
|
|
}
|
|
}
|
|
|
|
+ bool isReachableViaFallthrough =
|
|
+ std::find(MBB.pred_begin(), MBB.pred_end(), MBB.getPrevNode()) !=
|
|
+ MBB.pred_end();
|
|
// Emit an alignment directive for this block, if needed.
|
|
const Align Alignment = MBB.getAlignment();
|
|
- if (Alignment != Align(1))
|
|
- emitAlignment(Alignment);
|
|
+ if (Alignment != Align(1)) {
|
|
+ if (isReachableViaFallthrough)
|
|
+ emitAlignment(Alignment);
|
|
+ else
|
|
+ emitTrapAlignment(Alignment);
|
|
+ }
|
|
|
|
// Switch to a new section if this basic block must begin a section. The
|
|
// entry block is always placed in the function section and is handled
|