[GlobalMerge] Ensure that the MustKeepGlobalVariables has all globals from each landingpad clause.

[stefanp]

Summary

The filter clause in the landingpad may not have a GlobalVariable operand.
It may instead have a ConstantArray of operands and each operand within this
ConstantArray should also be checked to see if it is a GlobalVariable.

This patch add the check for the ConstantArray as well as a debug message that
outputs the contents of MustKeepGlobalVariables.

[lei]

LGTM
Thx!

[amyk]

Patch looks good to me, too. Thanks Stefan.

llvm/lib/CodeGen/GlobalMerge.cpp

611

nit: Unnecessary space?

[scui]

LGTM. Thanks!

[stefanp]

Rebased to top of trunk.
Removed the extra space.

llvm/lib/CodeGen/GlobalMerge.cpp

for (BasicBlock &BB : F) {
       if (!Pad->isEHPad())
         continue;
 
       // Keep globals used by landingpads and catchpads.
       for (const Use &U : Pad->operands()) {
         if (const GlobalVariable *GV =
                 dyn_cast<GlobalVariable>(U->stripPointerCasts()))
           MustKeepGlobalVariables.insert(GV);
+        else if (const ConstantArray *CA = dyn_cast<ConstantArray>(U->stripPointerCasts())) {
+          for (const Use &Elt : CA->operands()) {
+            if (const GlobalVariable *GV =
+                    dyn_cast<GlobalVariable>(Elt->stripPointerCasts()))
+              MustKeepGlobalVariables.insert(GV);
+          }
+        }
       }
     }
   }
 }
 
 bool GlobalMerge::doInitialization(Module &M) {
   if (!EnableGlobalMerge)
     return false;
 
   IsMachO = Triple(M.getTargetTriple()).isOSBinFormatMachO();
 
   auto &DL = M.getDataLayout();
   DenseMap<std::pair<unsigned, StringRef>, SmallVector<GlobalVariable *, 16>>
       Globals, ConstGlobals, BSSGlobals;
   bool Changed = false;
   setMustKeepGlobalVariables(M);
 
+  LLVM_DEBUG({
+      dbgs() << "Number of GV that must be kept:  " <<
+                MustKeepGlobalVariables.size() << "\n";
+      for (auto KeptGV = MustKeepGlobalVariables.begin();
+           KeptGV != MustKeepGlobalVariables.end(); KeptGV++)
+        dbgs() << "Kept: " << **KeptGV << "\n";
+  });
   // Grab all non-const globals.
   for (auto &GV : M.globals()) {
     // Merge is safe for "normal" internal or external globals only
     if (GV.isDeclaration() || GV.isThreadLocal() || GV.hasImplicitSection())
       continue;
 
     // It's not safe to merge globals that may be preempted
     if (TM && !TM->shouldAssumeDSOLocal(M, &GV))

llvm/test/Transforms/GlobalMerge/eh-filter.ll

+; RUN: opt -global-merge -debug-only=global-merge -S -o - %s 2>&1 | FileCheck %s
+
+;; Checks from the debug info.
+; CHECK:      Number of GV that must be kept:  5
+; CHECK-NEXT: Kept: @_ZTIi = external constant ptr
+; CHECK-NEXT: Kept: @_ZTIf = external constant ptr
+; CHECK-NEXT: Kept: @_ZTId = external constant ptr
+; CHECK-NEXT: Kept: @_ZTIc = external constant ptr
+; CHECK-NEXT: Kept: @_ZTIPi = external constant ptr
+
+;; Check that the landingpad, catch and filter have not changed.
+; CHECK:      %0 = landingpad { ptr, i32 }
+; CHECK-NEXT:         catch ptr @_ZTIi
+; CHECK-NEXT:         filter [5 x ptr] [ptr @_ZTIi, ptr @_ZTIf, ptr @_ZTId, ptr @_ZTIc, ptr @_ZTIPi]
+
+@_ZTIi = external constant ptr
+@_ZTIf = external constant ptr
+@_ZTId = external constant ptr
+@_ZTIc = external constant ptr
+@_ZTIPi = external constant ptr
+
+define noundef signext i32 @_Z6calleri(i32 noundef signext %a) local_unnamed_addr personality ptr @__xlcxx_personality_v1 {
+entry:
+  invoke void @_Z16callee_can_throwi(i32 noundef signext %a)
+          to label %return unwind label %lpad
+
+lpad:                                             ; preds = %entry
+  %0 = landingpad { ptr, i32 }
+          catch ptr @_ZTIi
+          filter [5 x ptr] [ptr @_ZTIi, ptr @_ZTIf, ptr @_ZTId, ptr @_ZTIc, ptr @_ZTIPi]
+  %1 = extractvalue { ptr, i32 } %0, 0
+  %2 = extractvalue { ptr, i32 } %0, 1
+  %3 = tail call i32 @llvm.eh.typeid.for(ptr nonnull @_ZTIi)
+  %matches = icmp eq i32 %2, %3
+  br i1 %matches, label %catch, label %filter.dispatch
+
+filter.dispatch:                                  ; preds = %lpad
+  %ehspec.fails = icmp slt i32 %2, 0
+  br i1 %ehspec.fails, label %ehspec.unexpected, label %eh.resume
+
+ehspec.unexpected:                                ; preds = %filter.dispatch
+  tail call void @__cxa_call_unexpected(ptr %1)
+  unreachable
+
+catch:                                            ; preds = %lpad
+  %4 = tail call ptr @__cxa_begin_catch(ptr %1)
+  %5 = load i32, ptr %4, align 4
+  tail call void @__cxa_end_catch()
+  br label %return
+
+return:                                           ; preds = %entry, %catch
+  %retval.0 = phi i32 [ %5, %catch ], [ 0, %entry ]
+  ret i32 %retval.0
+
+eh.resume:                                        ; preds = %filter.dispatch
+  resume { ptr, i32 } %0
+}
+
+declare void @_Z16callee_can_throwi(i32 noundef signext) local_unnamed_addr
+
+declare i32 @__xlcxx_personality_v1(...)
+
+declare i32 @llvm.eh.typeid.for(ptr)
+
+declare ptr @__cxa_begin_catch(ptr) local_unnamed_addr
+
+declare void @__cxa_end_catch() local_unnamed_addr
+
+declare void @__cxa_call_unexpected(ptr) local_unnamed_addr