[WinEH] Avoid infinite loop in BranchFolding for multiple single block funclets

Differential Revision: http://reviews.llvm.org/D14996

llvm-svn: 254629

llvm/lib/CodeGen/BranchFolding.cpp

@@ -1564,6 +1564,14 @@ ReoptimizeBlock:
       // removed, move this block to the end of the function.
       MachineBasicBlock *PrevTBB = nullptr, *PrevFBB = nullptr;
       SmallVector<MachineOperand, 4> PrevCond;
+      // We're looking for cases where PrevBB could possibly fall through to
+      // FallThrough, but if FallThrough is an EH pad that wouldn't be useful
+      // so here we skip over any EH pads so we might have a chance to find
+      // a branch target from PrevBB.
+      while (FallThrough != MF.end() && FallThrough->isEHPad())
+        ++FallThrough;
+      // Now check to see if the current block is sitting between PrevBB and
+      // a block to which it could fall through.
       if (FallThrough != MF.end() &&
           !TII->AnalyzeBranch(PrevBB, PrevTBB, PrevFBB, PrevCond, true) &&
           PrevBB.isSuccessor(&*FallThrough)) {

llvm/test/Transforms/BranchFolding/single-block-funclets.ll

@@ -0,0 +1,110 @@
+; RUN: llc -mtriple=x86_64-pc-windows-msvc < %s | FileCheck %s
+
+declare i32 @__CxxFrameHandler3(...)
+
+declare void @throw()
+declare i16 @f()
+
+define i16 @test1(i16 %a, i8* %b) personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  %cmp = icmp eq i16 %a, 10
+  br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+  %call1 = invoke i16 @f()
+          to label %cleanup unwind label %catch.dispatch
+
+if.else:
+  %call2 = invoke i16 @f()
+          to label %cleanup unwind label %catch.dispatch
+
+catch.dispatch:
+  catchpad [i8* null, i32 8, i8* null]
+          to label %catch unwind label %catch.dispatch.2
+
+catch:
+  invoke void @throw() noreturn
+          to label %unreachable unwind label %catchendblock
+
+catch.dispatch.2:
+  catchpad [i8* null, i32 64, i8* null]
+          to label %catch.2 unwind label %catchendblock
+
+catch.2:
+  store i8 1, i8* %b
+  invoke void @throw() noreturn
+          to label %unreachable unwind label %catchendblock
+
+catchendblock:
+  catchendpad unwind to caller
+
+cleanup:
+  %retval = phi i16 [ %call1, %if.then ], [ %call2, %if.else ]
+  ret i16 %retval
+
+unreachable:
+  unreachable
+}
+
+; This test verifies the case where two funclet blocks meet the old criteria
+; to be placed at the end.  The order of the blocks is not important for the
+; purposes of this test.  The failure mode is an infinite loop during
+; compilation.
+;
+; CHECK-LABEL: .def     test1;
+
+define i16 @test2(i16 %a, i8* %b) personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  %cmp = icmp eq i16 %a, 10
+  br i1 %cmp, label %if.then, label %if.else
+
+if.then:
+  %call1 = invoke i16 @f()
+          to label %cleanup unwind label %catch.dispatch
+
+if.else:
+  %call2 = invoke i16 @f()
+          to label %cleanup unwind label %catch.dispatch
+
+catch.dispatch:
+  catchpad [i8* null, i32 8, i8* null]
+          to label %catch unwind label %catch.dispatch.2
+
+catch:
+  invoke void @throw() noreturn
+          to label %unreachable unwind label %catchendblock
+
+catch.dispatch.2:
+  %c2 = catchpad [i8* null, i32 32, i8* null]
+          to label %catch.2 unwind label %catch.dispatch.3
+
+catch.2:
+  store i8 1, i8* %b
+  catchret %c2 to label %cleanup
+
+catch.dispatch.3:
+  %c3 = catchpad [i8* null, i32 64, i8* null]
+          to label %catch.3 unwind label %catchendblock
+
+catch.3:
+  store i8 2, i8* %b
+  catchret %c3 to label %cleanup
+
+catchendblock:
+  catchendpad unwind to caller
+
+cleanup:
+  %retval = phi i16 [ %call1, %if.then ], [ %call2, %if.else ], [ -1, %catch.2 ], [ -1, %catch.3 ]
+  ret i16 %retval
+
+unreachable:
+  unreachable
+}
+
+; This test verifies the case where three funclet blocks all meet the old
+; criteria to be placed at the end.  The order of the blocks is not important
+; for the purposes of this test.  The failure mode is an infinite loop during
+; compilation.
+;
+; CHECK-LABEL: .def     test2;
+