Chris Lattner 24ad00db5a Okay, so there is no reasonable way for tail duplication to update SSA form, ... as it is making effectively arbitrary modifications to the CFG and we don't have a domset/domfrontier implementations that can handle the dynamic updates. Instead of having a bunch of code that doesn't actually work in practice, just demote any potentially tricky values to the stack (causing the problem to go away entirely). Later invocations of mem2reg will rebuild SSA for us. This fixes all of the major performance regressions with tail duplication from LLVM 1.1. For example, this loop: --- int popcount(int x) { int result = 0; while (x != 0) { result = result + (x & 0x1); x = x >> 1; } return result; } --- Used to be compiled into: int %popcount(int %X) { entry: br label %loopentry loopentry: ; preds = %entry, %no_exit %x.0 = phi int [ %X, %entry ], [ %tmp.9, %no_exit ] ; <int> [#uses=3] %result.1.0 = phi int [ 0, %entry ], [ %tmp.6, %no_exit ] ; <int> [#uses=2] %tmp.1 = seteq int %x.0, 0 ; <bool> [#uses=1] br bool %tmp.1, label %loopexit, label %no_exit no_exit: ; preds = %loopentry %tmp.4 = and int %x.0, 1 ; <int> [#uses=1] %tmp.6 = add int %tmp.4, %result.1.0 ; <int> [#uses=1] %tmp.9 = shr int %x.0, ubyte 1 ; <int> [#uses=1] br label %loopentry loopexit: ; preds = %loopentry ret int %result.1.0 } And is now compiled into: int %popcount(int %X) { entry: br label %no_exit no_exit: ; preds = %entry, %no_exit %x.0.0 = phi int [ %X, %entry ], [ %tmp.9, %no_exit ] ; <int> [#uses=2] %result.1.0.0 = phi int [ 0, %entry ], [ %tmp.6, %no_exit ] ; <int> [#uses=1] %tmp.4 = and int %x.0.0, 1 ; <int> [#uses=1] %tmp.6 = add int %tmp.4, %result.1.0.0 ; <int> [#uses=2] %tmp.9 = shr int %x.0.0, ubyte 1 ; <int> [#uses=2] %tmp.1 = seteq int %tmp.9, 0 ; <bool> [#uses=1] br bool %tmp.1, label %loopexit, label %no_exit loopexit: ; preds = %no_exit ret int %tmp.6 } git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12457 91177308-0d34-0410-b5e6-96231b3b80d8		2004-03-16 23:29:09 +00:00
..
ADCE.cpp	Fix the count of the number of instructions removed	2004-02-01 05:15:07 +00:00
BasicBlockPlacement.cpp	Remove obsolete comment. Unreachable blocks will automatically be left at the	2004-02-11 05:20:50 +00:00
ConstantProp.cpp	Add header file I accidentally removed in teh shuffle	2004-01-12 19:15:20 +00:00
CorrelatedExprs.cpp	Remove use of the ConstantHandling interfaces	2004-01-12 19:12:50 +00:00
DCE.cpp	Finegrainify namespacification	2004-01-09 06:02:20 +00:00
DecomposeMultiDimRefs.cpp	Finegrainify namespacification	2004-01-09 06:02:20 +00:00
GCSE.cpp	Add counters for the number of calls elimianted	2004-03-15 05:46:59 +00:00
IndVarSimplify.cpp	Improve encapsulation in the Loop and LoopInfo classes by eliminating the	2004-01-08 00:09:44 +00:00
InstructionCombining.cpp	Add some debugging output	2004-03-13 23:54:27 +00:00
LICM.cpp	Implement LICM of calls in simple cases. This is sufficient to move around	2004-03-15 04:11:30 +00:00
Makefile	Added LLVM copyright notice to Makefiles.	2003-10-20 22:26:57 +00:00
PiNodeInsertion.cpp	Finegrainify namespacification	2004-01-09 06:02:20 +00:00
PRE.cpp	Finegrainify namespacification	2004-01-09 06:02:20 +00:00
Reassociate.cpp	Finegrainify namespacification	2004-01-09 06:02:20 +00:00
ScalarReplAggregates.cpp	Finegrainify namespacification	2003-12-02 17:43:55 +00:00
SCCP.cpp	Do not try to optimize PHI nodes with incredibly high degree. This reduces SCCP	2004-03-16 19:49:59 +00:00
SimplifyCFG.cpp	Finegrainify namespacification	2004-01-09 06:02:20 +00:00
SymbolStripping.cpp	Update obsolete comments	2004-01-10 21:36:49 +00:00
TailDuplication.cpp	Okay, so there is no reasonable way for tail duplication to update SSA form,	2004-03-16 23:29:09 +00:00
TailRecursionElimination.cpp	Adjust to the new BasicBlock ctor, which requires a function parameter	2004-02-04 03:58:28 +00:00