From 42d5f66fabc3766d45b0896f965eb04e29d42a5e Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Mon, 7 Oct 2019 22:19:40 +0000
Subject: [PATCH] [WebAssembly] Fix unwind mismatch stat computation

Summary:
There was a bug when computing the number of unwind destination
mismatches in CFGStackify. When there are many mismatched calls that
share the same (original) destination BB, they have to be counted
separately.

This also fixes a typo and runs `fixUnwindMismatches` only when the wasm
exception handling is enabled. This is to prevent unnecessary
computations and does not change behavior.

Reviewers: dschuff

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68552

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@373975 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp | 8 +++++---
 test/CodeGen/WebAssembly/cfg-stackify-eh.ll       | 4 ++++
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp b/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
index 6b2094679ce..d2a35574e2f 100644
--- a/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -848,7 +848,7 @@ bool WebAssemblyCFGStackify::fixUnwindMismatches(MachineFunction &MF) {
   SmallVector<const MachineBasicBlock *, 8> EHPadStack;
   // Range of intructions to be wrapped in a new nested try/catch
   using TryRange = std::pair<MachineInstr *, MachineInstr *>;
-  // In original CFG, <unwind destionation BB, a vector of try ranges>
+  // In original CFG, <unwind destination BB, a vector of try ranges>
   DenseMap<MachineBasicBlock *, SmallVector<TryRange, 4>> UnwindDestToTryRanges;
   // In new CFG, <destination to branch to, a vector of try ranges>
   DenseMap<MachineBasicBlock *, SmallVector<TryRange, 4>> BrDestToTryRanges;
@@ -985,7 +985,7 @@ bool WebAssemblyCFGStackify::fixUnwindMismatches(MachineFunction &MF) {
   // ...
   // cont:
   for (auto &P : UnwindDestToTryRanges) {
-    NumUnwindMismatches++;
+    NumUnwindMismatches += P.second.size();
 
     // This means the destination is the appendix BB, which was separately
     // handled above.
@@ -1300,7 +1300,9 @@ void WebAssemblyCFGStackify::placeMarkers(MachineFunction &MF) {
     }
   }
   // Fix mismatches in unwind destinations induced by linearizing the code.
-  fixUnwindMismatches(MF);
+  if (MCAI->getExceptionHandlingType() == ExceptionHandling::Wasm &&
+      MF.getFunction().hasPersonalityFn())
+    fixUnwindMismatches(MF);
 }
 
 void WebAssemblyCFGStackify::rewriteDepthImmediates(MachineFunction &MF) {
diff --git a/test/CodeGen/WebAssembly/cfg-stackify-eh.ll b/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
index c79eb935179..f33f56701eb 100644
--- a/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
+++ b/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
@@ -1,6 +1,7 @@
 ; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -exception-model=wasm -mattr=+exception-handling | FileCheck %s
 ; RUN: llc < %s -O0 -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -verify-machineinstrs -exception-model=wasm -mattr=+exception-handling | FileCheck %s --check-prefix=NOOPT
 ; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -exception-model=wasm -mattr=+exception-handling -wasm-disable-ehpad-sort | FileCheck %s --check-prefix=NOSORT
+; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -exception-model=wasm -mattr=+exception-handling -wasm-disable-ehpad-sort -stats 2>&1 | FileCheck %s --check-prefix=NOSORT-STAT
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
@@ -702,6 +703,9 @@ ehcleanup:                                        ; preds = %entry
   cleanupret from %0 unwind to caller
 }
 
+; Check if the unwind destination mismatch stats are correct
+; NOSORT-STAT: 11 wasm-cfg-stackify    - Number of EH pad unwind mismatches found
+
 declare void @foo()
 declare void @bar()
 declare i32 @baz()
-- 
2.40.0