ssa, so it has to be run really early in the pipeline. Any replacement
should probably use the SSAUpdater.

llvm-svn: 138841

llvm-svn: 138829

When walking backwards to eliminate final stores to allocas at the end of a function, encountering an unrelated store should not cause us to give up like encountering a load does.

llvm-svn: 138809

Optimize chained bitcasts of the form A->B->A.
Undo r138722 and change isEliminableCastPair to allow this case.

llvm-svn: 138756

llvm-svn: 138722

llvm-svn: 138651

- Reword comments.
- Allow undefined behavior interfering with undefined behavior.
- Add address space checks.

llvm-svn: 138619

SimplifyCFG: If we have a PHI node that can evaluate to NULL and do a load or store to the address returned by the PHI node then we can consider this incoming value as dead and remove the edge pointing there, unless there are instructions that can affect control flow executed in between.

In theory this could be extended to other instructions, eg. division by zero, but it's likely that it will "miscompile" some code because people depend on div by zero not trapping. NULL pointer dereference usually leads to a crash so we should be on the safe side.

This shrinks the size of a Release clang by 16k on x86_64.

llvm-svn: 138618

proper function to do it.

llvm-svn: 138550

getFirstNonPHI so that it will skip over the landingpad instructions as well.

llvm-svn: 138537

llvm-svn: 138481

insertion place.

llvm-svn: 138473

dominator information even though dominators were previously computed.

Patch by Nick Sumner.

llvm-svn: 138449

llvm-svn: 138243

llvm-svn: 138242

then don't split it a second time, since that block will be dead.

llvm-svn: 138153

llvm-svn: 138102

llvm-svn: 138025

C API functions must be able to see their extern "C" definitions, or it will be impossible to call them from C.

llvm-svn: 138022

known-incremented level, because the two concepts can be used
to prove the saftey of a retain+release removal in different
ways.

llvm-svn: 138016

We have to be careful when splitting the landing pad block, because the
landingpad instruction is required to remain as the first non-PHI of an invoke's
unwind edge. To retain this, we split the block into two blocks, moving the
predecessors within the loop to one block and the remaining predecessors to the
other. The landingpad instruction is cloned into the new blocks.

llvm-svn: 138015

SplitLandingPadPredecessors is similar to SplitBlockPredecessors in that it
splits the current block and attaches a set of predecessors to the new basic
block. However, it differs from SplitBlockPredecessors in that it's specifically
designed to handle landing pad blocks.

Two new basic blocks are created: one that is has the vector of predecessors as
its predecessors and one that has the remaining predecessors as its
predecessors. Those two new blocks then receive a cloned copy of the landingpad
instruction from the original block. The landingpad instructions are joined in a
PHI, etc. Like SplitBlockPredecessors, it updates the LLVM IR, AliasAnalysis,
DominatorTree, DominanceFrontier, LoopInfo, and LCCSA analyses.

llvm-svn: 138014

llvm-svn: 138008

llvm-svn: 137985

aren't from an indirect branch need to be dominated by the loop header.

llvm-svn: 137981

function.

llvm-svn: 137979

llvm-svn: 137978

of debug info.

llvm-svn: 137972

llvm-svn: 137959

functionality change.

llvm-svn: 137926

Dramatically speedup codegen prepare by a) avoiding use of dominator tree and b) doing a separate pass over dbg.value instructions.

llvm-svn: 137908

llvm-svn: 137890

llvm-svn: 137888

PRE needs the landing pads to have their critical edges split. Doing this for a
landing pad is non-trivial. Abandon the attempt to perform PRE when we come
across a landing pad. (Reviewed by Owen!)

llvm-svn: 137876

llvm-svn: 137872

One way to exit the loop is through an unwind edge. However, that may involve
splitting the critical edge of the landing pad, which is non-trivial. Prevent
the transformation from rewriting the landing pad exit loop block.

llvm-svn: 137871

so requires more care than this generic algorithm should handle.

llvm-svn: 137866

instruction should be marked as potentially reading and/or writing memory.

llvm-svn: 137863

Silly mistake from r137777; restore significant isStructTy() checks.  While here, be a bit more defensive
with unknown instructions.

Fixes PR10687.

llvm-svn: 137836

making random bad assumptions about instructions which are not explicitly listed.  

Includes fix for rdar://9956541, a version of "undef ^ undef should return
0 because it's easier than arguing with users".

llvm-svn: 137777