Mark setjmp as "returns twice" and turn off SimpleCoalescing when called.

src/IceTargetLoweringX8632.cpp

 //===- subzero/src/IceTargetLoweringX8632.cpp - x86-32 lowering -----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the TargetLoweringX8632 class, which
@@ skipping 629 matching lines @@
   //  * GlobalsSize:            area 4
   //  * GlobalsAndSubsequentPaddingSize: areas 4 - 5
   //  * LocalsSpillAreaSize:    area 6
   //  * SpillAreaSizeBytes:     areas 3 - 7
 
   // If SimpleCoalescing is false, each variable without a register
   // gets its own unique stack slot, which leads to large stack
   // frames.  If SimpleCoalescing is true, then each "global" variable
   // without a register gets its own slot, but "local" variable slots
   // are reused across basic blocks.  E.g., if A and B are local to
-  // block 1 and C is local to block 2, then C may share a slot with A
-  // or B.
-  const bool SimpleCoalescing = true;
+  // block 1 and C is local to block 2, then C may share a slot with A or B.
+  //
+  // We cannot coalesce stack slots if this function calls a "returns twice"
+  // function. In that case, basic blocks may be revisited, and variables
+  // local to those basic blocks are actually live until after the
+  // called function returns a second time.
+  const bool SimpleCoalescing = !callsReturnsTwice();
   size_t InArgsSizeBytes = 0;
   size_t PreservedRegsSizeBytes = 0;
   SpillAreaSizeBytes = 0;
   Context.init(Node);
   Context.setInsertPoint(Context.getCur());
 
   // Determine stack frame offsets for each Variable without a
   // register assignment.  This can be done as one variable per stack
   // slot.  Or, do coalescing by running the register allocator again
   // with an infinite set of registers (as a side effect, this gives
@@ skipping 3794 matching lines @@
     Str << "\t.align\t" << Align << "\n";
     Str << MangledName << ":\n";
     for (SizeT i = 0; i < Size; ++i) {
       Str << "\t.byte\t" << (((unsigned)Data[i]) & 0xff) << "\n";
     }
     Str << "\t.size\t" << MangledName << ", " << Size << "\n";
   }
 }
 
 } // end of namespace Ice