[PATCH] [WinEH] Fix problem with mapping handler blocks when multiple clauses share a handler implementation.

[Andy Kaylor]

Hi majnemer, rnk,

This addresses a failure which could occur when optimized IR eliminated handler-specific blocks and created a single shared handler representation.  The IR unconditionally flows into a handler block even when a selector dispatch would normally be expected.  I believe this can only happen if the landing pad has a catch-all handler and the handlers for prior clauses are identical to the catch-all implementation with no intervening clean-up.

My proposed solution effectively eliminates the type-specific catch handlers from the final IR produced, but I think this is good because the resulting code will be more compact yet functionally equivalent.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D9125

Files:
  lib/CodeGen/WinEHPrepare.cpp
  test/CodeGen/WinEH/cppeh-shared-empty-catch.ll

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