Reland "[WebAssembly] LSDA info generation"
Summary:
This adds support for LSDA (exception table) generation for wasm EH.
Wasm EH mostly follows the structure of Itanium-style exception tables,
with one exception: a call site table entry in wasm EH corresponds to
not a call site but a landing pad.
In wasm EH, the VM is responsible for stack unwinding. After an
exception occurs and the stack is unwound, the control flow is
transferred to wasm 'catch' instruction by the VM, after which the
personality function is called from the compiler-generated code. (Refer
to WasmEHPrepare pass for more information on this part.)
This patch:
- Changes wasm.landingpad.index intrinsic to take a token argument, to
make this 1:1 match with a catchpad instruction
- Stores landingpad index info and catch type info MachineFunction in
before instruction selection
- Lowers wasm.lsda intrinsic to an MCSymbol pointing to the start of an
exception table
- Adds WasmException class with overridden methods for table generation
- Adds support for LSDA section in Wasm object writer
Reviewers: dschuff, sbc100, rnk
Subscribers: mgorny, jgravelle-google, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D52748
llvm-svn: 345345
diff --git a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h
index b89421a..e3a6f8e9 100644
--- a/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h
+++ b/llvm/lib/CodeGen/AsmPrinter/EHStreamer.h
@@ -85,9 +85,10 @@
/// zero for the landing pad and the action. Calls marked 'nounwind' have
/// no entry and must not be contained in the try-range of any entry - they
/// form gaps in the table. Entries must be ordered by try-range address.
- void computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
- const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
- const SmallVectorImpl<unsigned> &FirstActions);
+ virtual void computeCallSiteTable(
+ SmallVectorImpl<CallSiteEntry> &CallSites,
+ const SmallVectorImpl<const LandingPadInfo *> &LandingPads,
+ const SmallVectorImpl<unsigned> &FirstActions);
/// Emit landing pads and actions.
///
@@ -108,7 +109,9 @@
/// found the frame is unwound and handling continues.
/// 3. Type id table contains references to all the C++ typeinfo for all
/// catches in the function. This tables is reversed indexed base 1.
- void emitExceptionTable();
+ ///
+ /// Returns the starting symbol of an exception table.
+ MCSymbol *emitExceptionTable();
virtual void emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel);