[WebAssembly] Restore stack pointer right after catch instruction

Summary:
After the staack is unwound due to a thrown exxception,
`__stack_pointer` global can point to an invalid address. So
a `global.set` to restore `__stack_pointer` should be inserted right
after `catch` instruction.

But after r352598 the `global.set` instruction is inserted not right
after `catch` but after `block` - `br-on-exn` - `end_block` -
`extract_exception` sequence. This CL fixes it.

While doing that, we can actually move ReplacePhysRegs pass after
LateEHPrepare and merge EHRestoreStackPointer pass into LateEHPrepare,
and now placing `global.set` to `__stack_pointer` right after `catch` is
much easier. Otherwise it is hard to guarantee that `global.set` is
still right after `catch` and not touched with other transformations, in
which case we have to do something to hoist it.

Reviewers: dschuff

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

Differential Revision: https://reviews.llvm.org/D57421

llvm-svn: 352681

1 files changed, 5 insertions, 9 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
index c235fd21d06..80e34b307e1 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -57,7 +57,6 @@ extern "C" void LLVMInitializeWebAssemblyTarget() {
   initializeOptimizeReturnedPass(PR);
   initializeWebAssemblyArgumentMovePass(PR);
   initializeWebAssemblySetP2AlignOperandsPass(PR);
-  initializeWebAssemblyEHRestoreStackPointerPass(PR);
   initializeWebAssemblyReplacePhysRegsPass(PR);
   initializeWebAssemblyPrepareForLiveIntervalsPass(PR);
   initializeWebAssemblyOptimizeLiveIntervalsPass(PR);
@@ -284,14 +283,6 @@ void WebAssemblyPassConfig::addPostRegAlloc() {
 void WebAssemblyPassConfig::addPreEmitPass() {
   TargetPassConfig::addPreEmitPass();
 
-  // Restore __stack_pointer global after an exception is thrown.
-  addPass(createWebAssemblyEHRestoreStackPointer());
-
-  // Now that we have a prologue and epilogue and all frame indices are
-  // rewritten, eliminate SP and FP. This allows them to be stackified,
-  // colored, and numbered with the rest of the registers.
-  addPass(createWebAssemblyReplacePhysRegs());
-
   // Rewrite pseudo call_indirect instructions as real instructions.
   // This needs to run before register stackification, because we change the
   // order of the arguments.
@@ -304,6 +295,11 @@ void WebAssemblyPassConfig::addPreEmitPass() {
   // Every CFG-changing optimizations should come before this.
   addPass(createWebAssemblyLateEHPrepare());
 
+  // Now that we have a prologue and epilogue and all frame indices are
+  // rewritten, eliminate SP and FP. This allows them to be stackified,
+  // colored, and numbered with the rest of the registers.
+  addPass(createWebAssemblyReplacePhysRegs());
+
   // Preparations and optimizations related to register stackification.
   if (getOptLevel() != CodeGenOpt::None) {
     // LiveIntervals isn't commonly run this late. Re-establish preconditions.