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Author SHA1 Message Date
Chris Lattner 95057f6ad1 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
}

llvm-svn: 12457
 2004-03-16 23:29:09 +00:00
Chris Lattner a64923ad26 Do not copy gigantic switch instructions 
llvm-svn: 12441
 2004-03-16 19:45:22 +00:00
Chris Lattner 5cf39339d1 Disable tail duplication in a case that breaks on Olden/tsp 
llvm-svn: 12021
 2004-03-01 01:12:13 +00:00
Chris Lattner bf2963ef91 Fix PR255: [tailduplication] Single basic block loops are very rare 
Note that this is a band-aid put over a band-aid.  This just undisables
tail duplication in on very specific case that it seems to work in.

llvm-svn: 11989
 2004-02-29 06:41:20 +00:00
Chris Lattner 8d0bacbb9e Implement Transforms/InstCombine/cast.ll:test13, a case which occurs in a 
hot 164.gzip loop.

llvm-svn: 11702
 2004-02-22 05:25:17 +00:00
Chris Lattner ed9b12c31a Disable tail duplication in any "hard" cases, where it might break SSA form. 
llvm-svn: 11052
 2004-02-01 06:32:28 +00:00
Chris Lattner 49525f8cf4 Finegrainify namespacification 
llvm-svn: 10725
 2004-01-09 06:02:20 +00:00
Brian Gaeke 960707c335 Put all LLVM code into the llvm namespace, as per bug 109. 
llvm-svn: 9903
 2003-11-11 22:41:34 +00:00
John Criswell 482202a601 Added LLVM project notice to the top of every C++ source file. 
Header files will be on the way.

llvm-svn: 9298
 2003-10-20 19:43:21 +00:00
Chris Lattner 1c884e18e1 Fix bug: TailDuplicate/2003-08-31-UnreachableBlocks.ll 
llvm-svn: 8276
 2003-08-31 21:17:44 +00:00
Chris Lattner bb4dd7ed34 Fix bug: TailDup/2003-08-23-InvalidatedPointers.ll 
llvm-svn: 8078
 2003-08-23 20:08:30 +00:00
Chris Lattner 8abcd56c74 DEBUG got moved to Support/Debug.h 
llvm-svn: 7492
 2003-08-01 22:15:03 +00:00
Chris Lattner d78ebd0c6b Fix bug: TailDup/2003-07-22-InfiniteLoop.ll 
llvm-svn: 7243
 2003-07-23 03:32:41 +00:00
Chris Lattner f7544873de Fix bug: TailDup/2003-06-24-Simpleloop.ll 
llvm-svn: 6881
 2003-06-24 19:48:06 +00:00
Chris Lattner 92963de6fa Add paranoia checking 
llvm-svn: 6856
 2003-06-22 20:46:00 +00:00
Chris Lattner 268c1392da Test change 
llvm-svn: 6852
 2003-06-22 20:25:27 +00:00
Chris Lattner a5434caa5c Initial checkin of Tail duplication pass. 
llvm-svn: 6846
 2003-06-22 20:10:28 +00:00