Sanjay Patel 959b276771 transform fadd chains to increase parallelism ... This is a compromise: with this simple patch, we should always handle a chain of exactly 3 operations optimally, but we're not generating the optimal balanced binary tree for a longer sequence. In general, this transform will reduce the dependency chain for a sequence of instructions using N operands from a worst case N-1 dependent operations to N/2 dependent operations. The optimal balanced binary tree would reduce the chain to log2(N). The trade-off for not dealing with longer sequences is: (1) we have less complexity in the compiler, (2) we avoid unknown compile-time blowup calculating a balanced tree, and (3) we don't need to worry about the increased register pressure required to parallelize longer sequences. It also seems unlikely that we would ever encounter really long strings of dependent ops like that in the wild, but I'm not sure how to verify that speculation. FWIW, I see no perf difference for test-suite running on btver2 (x86-64) with -ffast-math and this patch. We can extend this patch to cover other associative operations such as fmul, fmax, fmin, integer add, integer mul. This is a partial fix for: https://llvm.org/bugs/show_bug.cgi?id=17305 and if extended: https://llvm.org/bugs/show_bug.cgi?id=21768 https://llvm.org/bugs/show_bug.cgi?id=23116 The issue also came up in: http://reviews.llvm.org/D8941 Differential Revision: http://reviews.llvm.org/D9232 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236031 91177308-0d34-0410-b5e6-96231b3b80d8		2015-04-28 21:03:22 +00:00
..
Analysis	[getUnderlyingOjbects] Analyze loop PHIs further to remove false positives	2015-04-23 20:09:20 +00:00
Assembler	IR: Add assembly/bitcode support for function metadata attachments	2015-04-24 22:04:41 +00:00
Bindings
Bitcode	Relax an assert when there's a type mismatch in forward references	2015-04-28 20:18:47 +00:00
BugPoint	bugpoint Enhancement.	2015-04-20 23:42:22 +00:00
CodeGen	transform fadd chains to increase parallelism	2015-04-28 21:03:22 +00:00
DebugInfo	Reapply r235977 "[DebugInfo] Add debug locations to constant SD nodes"	2015-04-28 14:05:47 +00:00
ExecutionEngine	[opaque pointer type] Add textual IR support for explicit type parameter to the call instruction	2015-04-16 23:24:18 +00:00
Feature	[opaque pointer type] Add textual IR support for explicit type parameter to the call instruction	2015-04-16 23:24:18 +00:00
FileCheck
Instrumentation	[opaque pointer type] Add textual IR support for explicit type parameter to the call instruction	2015-04-16 23:24:18 +00:00
Integer	[opaque pointer type] Add textual IR support for explicit type parameter to the call instruction	2015-04-16 23:24:18 +00:00
JitListener
Linker	Linker: Copy over function metadata attachments	2015-04-24 22:07:31 +00:00
LTO	Revert changes to LTO test case since llvm-lto can't handle textual IR inputs	2015-04-24 18:13:27 +00:00
MC	[mips] [IAS] Do not generate redundant ORi in createLShiftOri.	2015-04-28 14:06:35 +00:00
Object	Support arm32 R_ARM_V4BX relocation format	2015-04-22 15:26:43 +00:00
Other	[opaque pointer type] Add textual IR support for explicit type parameter to the call instruction	2015-04-16 23:24:18 +00:00
SymbolRewriter
TableGen	Add support for v1i128 type.	2015-04-17 16:11:05 +00:00
tools	Make llvm-symbolizer work on Windows.	2015-04-27 17:19:51 +00:00
Transforms	Constfold insertelement to undef when index is out-of-bounds	2015-04-27 09:30:49 +00:00
Unit
Verifier	[opaque pointer type] Add textual IR support for explicit type parameter to the invoke instruction	2015-04-24 19:32:54 +00:00
YAMLParser
.clang-format
CMakeLists.txt
lit.cfg
lit.site.cfg.in
Makefile
Makefile.tests
TestRunner.sh