[WebAssembly] Make rethrow take an except_ref type argument

Summary:
In the new wasm EH proposal, `rethrow` takes an `except_ref` argument.
This change was missing in r352598.

This patch adds `llvm.wasm.rethrow.in.catch` intrinsic. This is an
intrinsic that's gonna eventually be lowered to wasm `rethrow`
instruction, but this intrinsic can appear only within a catchpad or a
cleanuppad scope. Also this intrinsic needs to be invokable - otherwise
EH pad successor for it will not be correctly generated in clang.

This also adds lowering logic for this intrinsic in
`SelectionDAGBuilder::visitInvoke`. This routine is basically a
specialized and simplified version of
`SelectionDAGBuilder::visitTargetIntrinsic`, but we can't use it
because if is only for `CallInst`s.

This deletes the previous `llvm.wasm.rethrow` intrinsic and related
tests, which was meant to be used within a `__cxa_rethrow` library
function. Turned out this needs some more logic, so the intrinsic for
this purpose will be added later.

LateEHPrepare takes a result value of `catch` and inserts it into
matching `rethrow` as an argument.

`RETHROW_IN_CATCH` is a pseudo instruction that serves as a link between
`llvm.wasm.rethrow.in.catch` and the real wasm `rethrow` instruction. To
generate a `rethrow` instruction, we need an `except_ref` argument,
which is generated from `catch` instruction. But `catch` instrutions are
added in LateEHPrepare pass, so we use `RETHROW_IN_CATCH`, which takes
no argument, until we are able to correctly lower it to `rethrow` in
LateEHPrepare.

Reviewers: dschuff

Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59352

llvm-svn: 356316

1 files changed, 14 insertions, 5 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
index 5b6fdb86c6d..f365aa73792 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyLateEHPrepare.cpp
@@ -161,9 +161,17 @@ bool WebAssemblyLateEHPrepare::replaceFuncletReturns(MachineFunction &MF) {
       Changed = true;
       break;
     }
-    case WebAssembly::CLEANUPRET: {
-      // Replace a cleanupret with a rethrow
-      BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::RETHROW));
+    case WebAssembly::CLEANUPRET:
+    case WebAssembly::RETHROW_IN_CATCH: {
+      // Replace a cleanupret/rethrow_in_catch with a rethrow
+      auto *EHPad = getMatchingEHPad(TI);
+      auto CatchPos = EHPad->begin();
+      if (CatchPos->isEHLabel()) // EH pad starts with an EH label
+        ++CatchPos;
+      MachineInstr *Catch = &*CatchPos;
+      unsigned ExnReg = Catch->getOperand(0).getReg();
+      BuildMI(MBB, TI, TI->getDebugLoc(), TII.get(WebAssembly::RETHROW))
+          .addReg(ExnReg);
       TI->eraseFromParent();
       Changed = true;
       break;
@@ -191,7 +199,8 @@ bool WebAssemblyLateEHPrepare::removeUnnecessaryUnreachables(
       SmallVector<MachineBasicBlock *, 8> Succs(MBB.succ_begin(),
                                                 MBB.succ_end());
       for (auto *Succ : Succs)
-        MBB.removeSuccessor(Succ);
+        if (!Succ->isEHPad())
+          MBB.removeSuccessor(Succ);
       eraseDeadBBsAndChildren(Succs);
     }
   }
@@ -337,7 +346,7 @@ bool WebAssemblyLateEHPrepare::addExceptionExtraction(MachineFunction &MF) {
       BuildMI(ElseMBB, DL, TII.get(WebAssembly::UNREACHABLE));
 
     } else {
-      BuildMI(ElseMBB, DL, TII.get(WebAssembly::RETHROW));
+      BuildMI(ElseMBB, DL, TII.get(WebAssembly::RETHROW)).addReg(ExnReg);
       if (EHInfo->hasEHPadUnwindDest(EHPad))
         ElseMBB->addSuccessor(EHInfo->getEHPadUnwindDest(EHPad));
     }