[PATCH] D68552: [WebAssembly] Fix unwind mismatch stat computation

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
aheejin added a reviewer: dschuff.
Herald added subscribers: llvm-commits, sunfish, hiraditya, jgravelle-google, sbc100.
Herald added a project: LLVM.

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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D68552

Files:
  llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
  llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll


Index: llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
===================================================================
--- llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll
+++ llvm/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"
@@ -664,6 +665,9 @@
   ret void
 }
 
+; 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()
Index: llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
===================================================================
--- llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -848,7 +848,7 @@
   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 @@
   // ...
   // 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 @@
     }
   }
   // 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) {


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