Use assembler expressions to lay out the EH LSDA.
Rely on the assembler to finalize the layout of the DWARF/Itanium
exception-handling LSDA. Rather than calculate the exact size of each
thing in the LSDA, use assembler directives:
To emit the offset to the TTBase label:
.uleb128 .Lttbase0-.Lttbaseref0
.Lttbaseref0:
To emit the size of the call site table:
.uleb128 .Lcst_end0-.Lcst_begin0
.Lcst_begin0:
... call site table entries ...
.Lcst_end0:
To align the type info table:
... action table ...
.balign 4
.long _ZTIi
.long _ZTIl
.Lttbase0:
Using assembler directives simplifies the compiler and allows switching
the encoding of offsets in the call site table from udata4 to uleb128 for
a large code size savings. (This commit does not change the encoding.)
The combination of the uleb128 followed by a balign creates an unfortunate
dependency cycle that the assembler must sometimes resolve either by
padding an LEB or by inserting zero padding before the type table. See
PR35809 or GNU as bug 4029.
Patch by Ryan Prichard!
llvm-svn: 324749
diff --git a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h
index 28bceab..ab3bd5d 100644
--- a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h
+++ b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h
@@ -72,9 +72,9 @@
/// Compute the actions table and gather the first action index for each
/// landing pad site.
- unsigned computeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs,
- SmallVectorImpl<ActionEntry> &Actions,
- SmallVectorImpl<unsigned> &FirstActions);
+ void computeActionsTable(const SmallVectorImpl<const LandingPadInfo *> &LPs,
+ SmallVectorImpl<ActionEntry> &Actions,
+ SmallVectorImpl<unsigned> &FirstActions);
void computePadMap(const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
RangeMapType &PadMap);
@@ -110,7 +110,7 @@
/// catches in the function. This tables is reversed indexed base 1.
void emitExceptionTable();
- virtual void emitTypeInfos(unsigned TTypeEncoding);
+ virtual void emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel);
// Helpers for identifying what kind of clause an EH typeid or selector
// corresponds to. Negative selectors are for filter clauses, the zero