llvm/lib
Chandler Carruth c13c09106e [SCEV] Add some asserts to the recently improved trip count computation
routines and fix all of the bugs they expose.

I hit a test case that crashed even without these asserts due to passing
a non-exiting latch to the ExitingBlock parameter of the trip count
computation machinery. However, when I add the nice asserts, it turns
out we have plenty of coverage of these bugs, they just didn't manifest
in crashers.

The core problem seems to stem from an assumption that the latch *is*
the exiting block. While this is often true, and somewhat the "normal"
way to think about loops, it isn't necessarily true. The correct way to
call the trip count routines in a *generic* fashion (that is, without
a particular exit in mind) is to just use the loop's single exiting
block if it has one. The trip count can't be computed generically unless
it does. This works great for the loop vectorizer. The loop unroller
actually *wants* to select the latch when it has to chose between
multiple exits because for unrolling it is the latch trips that matter.
But if this is the desire, it needs to explicitly guard for non-exiting
latches and check for the generic trip count in that case.

I've added the asserts, and added convenience APIs for querying the trip
count generically that check for a single exit block. I've kept the APIs
consistent between computing trip count and trip multiples.

Thansk to Mark for the help debugging and tracking down the *right* fix
here!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219550 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-11 00:12:11 +00:00
..
Analysis [SCEV] Add some asserts to the recently improved trip count computation 2014-10-11 00:12:11 +00:00
AsmParser Make CallingConv::ID an alias of "unsigned". 2014-09-10 18:00:17 +00:00
Bitcode Do not destroy external linkage when deleting function body 2014-09-23 12:54:19 +00:00
CodeGen Revert "DebugInfo: Ensure that all debug location scope chains from instructions within a function, lead to the function itself." 2014-10-10 18:46:21 +00:00
DebugInfo Add couple of missing 'override' keyword. NFC. 2014-10-10 17:34:30 +00:00
ExecutionEngine [MCJIT] Replace memcpy with readBytesUnaligned in RuntimeDyldMachOI386. 2014-10-10 23:07:09 +00:00
IR Return undef on FP <-> Int conversions that overflow (PR21330). 2014-10-10 23:00:21 +00:00
IRReader Pass a && to getLazyBitcodeModule. 2014-09-03 17:31:46 +00:00
LineEditor [CMake] Use LINK_LIBS instead of target_link_libraries(). 2014-02-26 06:41:29 +00:00
Linker Merge alignment of common GlobalValue. 2014-09-09 17:48:18 +00:00
LTO LTO: Document the Boolean argument from r218784 2014-10-02 21:11:04 +00:00
MC delete function name from comment 2014-10-09 21:23:39 +00:00
Object Object, COFF: Move the VirtualSize/SizeOfRawData logic to getSectionSize 2014-10-09 08:42:31 +00:00
Option Add an overload of getLastArgNoClaim taking two OptSpecifiers. 2014-09-12 19:42:53 +00:00
ProfileData Reduce double set lookups. NFC. 2014-10-10 15:32:50 +00:00
Support Follow-up to r219534 to make symbolization more robust. 2014-10-10 22:58:26 +00:00
TableGen Eliminate some deep std::vector copies. NFC. 2014-10-03 18:33:16 +00:00
Target R600/SI: Change how DS offsets are printed 2014-10-10 22:16:07 +00:00
Transforms [SCEV] Add some asserts to the recently improved trip count computation 2014-10-11 00:12:11 +00:00
CMakeLists.txt ProfileData: Introduce the InstrProfReader interface and a text reader 2014-03-21 17:24:48 +00:00
LLVMBuild.txt ProfileData: Introduce the InstrProfReader interface and a text reader 2014-03-21 17:24:48 +00:00
Makefile ProfileData: Introduce the InstrProfReader interface and a text reader 2014-03-21 17:24:48 +00:00