First half of PR40800, this patch adds DAG undef handling to icmp instructions to match the behaviour in llvm::ConstantFoldCompareInstruction and SimplifyICmpInst, this permits constant folding of vector comparisons where some elements had been reduced to UNDEF (by SimplifyDemandedVectorElts etc.).
This involved a lot of tweaking to reduced tests as bugpoint loves to reduce icmp arguments to undef........
Differential Revision: https://reviews.llvm.org/D59363
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356938 91177308-0d34-0410-b5e6-96231b3b80d8
Tail merge was making the assumption that a layout successor or
predecessor was always a cfg successor/predecessor. Remove that
assumption. Changes to tests are necessary because the errant cfg edges
were preventing optimizations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273700 91177308-0d34-0410-b5e6-96231b3b80d8
Targets like SPARC and MIPS have delay slots and normally bundle the
delay slot instruction with the corresponding terminator.
Teach isBlockOnlyReachableByFallthrough to find any MBB operands on
bundled terminators so SPARC doesn't need to specialize this function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199061 91177308-0d34-0410-b5e6-96231b3b80d8
Simon Pilgrim