[Constant Hoisting] ConstantHoisting pass illegally modifies EHPad

[rnk]

Summary

Fix for PR32107

[rnk]

I made some formatting and test robustness changes, so I'll take this diff and land it soon.

[rnk]

• formatting and test changes

lib/Transforms/Scalar/ConstantHoisting.cpp

if (!isa<PHINode>(Inst) && !Inst->isEHPad())
     return Inst;
 
   // We can't insert directly before a phi node or an eh pad. Insert before
   // the terminator of the incoming or dominating block.
   assert(Entry != Inst->getParent() && "PHI or landing pad in entry block!");
   if (Idx != ~0U && isa<PHINode>(Inst))
     return cast<PHINode>(Inst)->getIncomingBlock(Idx)->getTerminator();
 
-  BasicBlock *IDom = DT->getNode(Inst->getParent())->getIDom()->getBlock();
-  return IDom->getTerminator();
+  // This must be an EH pad. Iterate over immediate dominators until we find a
+  // non-EH pad. We need to skip over catchswitch blocks, which are both EH pads
+  // and terminators.
+  auto IDom = DT->getNode(Inst->getParent())->getIDom();
+  while (IDom->getBlock()->isEHPad()) {
+    assert(Entry != IDom->getBlock() && "eh pad in entry block");
+    IDom = IDom->getIDom();
+  }
+
+  return IDom->getBlock()->getTerminator();
 }
 
 /// \brief Find an insertion point that dominates all uses.
 Instruction *ConstantHoistingPass::findConstantInsertionPoint(
     const ConstantInfo &ConstInfo) const {
   assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
   // Collect all basic blocks.
   SmallPtrSet<BasicBlock *, 8> BBs;

test/Transforms/ConstantHoisting/X86/ehpad.ll

+; RUN: opt -S -consthoist < %s | FileCheck %s
+
+; FIXME: The catchpad doesn't even use the constant, so a better fix would be to
+; insert the bitcast in the catchpad block.
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+; CHECK-LABEL: define i32 @main
+; CHECK: %tobool = icmp eq i32 %argc, 0
+; CHECK-NEXT: bitcast i64 9209618997431186100 to i64
+; CHECK-NEXT: br i1 %tobool
+
+; Function Attrs: norecurse
+define i32 @main(i32 %argc, i8** nocapture readnone %argv) local_unnamed_addr #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+  %call = tail call i64 @fn(i64 0)
+  %call1 = tail call i64 @fn(i64 1)
+  %tobool = icmp eq i32 %argc, 0
+  br i1 %tobool, label %2, label %1
+
+; <label>:1:                                      ; preds = %0
+  %call2 = invoke i64 @fn(i64 %call)
+          to label %6 unwind label %catch.dispatch
+
+; <label>:2:                                      ; preds = %0
+  %call3 = invoke i64 @fn(i64 %call1)
+          to label %6 unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %2, %1
+  %z.0 = phi i64 [ %call, %1 ], [ %call1, %2 ]
+  %3 = catchswitch within none [label %4] unwind to caller
+
+; <label>:4:                                      ; preds = %catch.dispatch
+  %5 = catchpad within %3 [i8* null, i32 64, i8* null]
+  br i1 %tobool, label %then, label %else
+
+then:
+  %call4 = tail call i64 @fn(i64 %z.0) [ "funclet"(token %5) ]
+  %add = add i64 %call4, 9209618997431186100
+  br label %endif
+
+else:
+  %call5 = tail call i64 @fn(i64 0) [ "funclet"(token %5) ]
+  %add6 = add i64 %call5, 9209618997431186100
+  br label %endif
+
+endif:
+  %v = phi i64 [ %add, %then ], [ %add6, %else ]
+  %call7 = tail call i64 @fn(i64 %v) [ "funclet"(token %5) ]
+  %call8 = tail call i64 @fn(i64 %call7) [ "funclet"(token %5) ]
+  catchret from %5 to label %6
+
+; <label>:6:                                      ; preds = %1, %2, %4
+  ret i32 0
+}
+
+declare i64 @fn(i64) local_unnamed_addr #1
+
+declare i32 @__CxxFrameHandler3(...)
+
+attributes #0 = { norecurse "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "stack-protector-buffer-size"="8" "target-features"="+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "stack-protector-buffer-size"="8" "target-features"="+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }