6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-10-06 14:57:41 +00:00
Code Issues Projects Releases Wiki Activity
5d37370a6f
llvm-6502/test/Transforms
History
Chris Lattner 5d37370a6f When loop rotation happens, it is *very* common for the duplicated condbr 
to be foldable into an uncond branch.  When this happens, we can make a
much simpler CFG for the loop, which is important for nested loop cases
where we want the outer loop to be aggressively optimized.

Handle this case more aggressively.  For example, previously on
phi-duplicate.ll we would get this:


define void @test(i32 %N, double* %G) nounwind ssp {
entry:
  %cmp1 = icmp slt i64 1, 1000
  br i1 %cmp1, label %bb.nph, label %for.end

bb.nph:                                           ; preds = %entry
  br label %for.body

for.body:                                         ; preds = %bb.nph, %for.cond
  %j.02 = phi i64 [ 1, %bb.nph ], [ %inc, %for.cond ]
  %arrayidx = getelementptr inbounds double* %G, i64 %j.02
  %tmp3 = load double* %arrayidx
  %sub = sub i64 %j.02, 1
  %arrayidx6 = getelementptr inbounds double* %G, i64 %sub
  %tmp7 = load double* %arrayidx6
  %add = fadd double %tmp3, %tmp7
  %arrayidx10 = getelementptr inbounds double* %G, i64 %j.02
  store double %add, double* %arrayidx10
  %inc = add nsw i64 %j.02, 1
  br label %for.cond

for.cond:                                         ; preds = %for.body
  %cmp = icmp slt i64 %inc, 1000
  br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge

for.cond.for.end_crit_edge:                       ; preds = %for.cond
  br label %for.end

for.end:                                          ; preds = %for.cond.for.end_crit_edge, %entry
  ret void
}

Now we get the much nicer:

define void @test(i32 %N, double* %G) nounwind ssp {
entry:
  br label %for.body

for.body:                                         ; preds = %entry, %for.body
  %j.01 = phi i64 [ 1, %entry ], [ %inc, %for.body ]
  %arrayidx = getelementptr inbounds double* %G, i64 %j.01
  %tmp3 = load double* %arrayidx
  %sub = sub i64 %j.01, 1
  %arrayidx6 = getelementptr inbounds double* %G, i64 %sub
  %tmp7 = load double* %arrayidx6
  %add = fadd double %tmp3, %tmp7
  %arrayidx10 = getelementptr inbounds double* %G, i64 %j.01
  store double %add, double* %arrayidx10
  %inc = add nsw i64 %j.01, 1
  %cmp = icmp slt i64 %inc, 1000
  br i1 %cmp, label %for.body, label %for.end

for.end:                                          ; preds = %for.body
  ret void
}

With all of these recent changes, we are now able to compile:

void foo(char *X) {
 for (int i = 0; i != 100; ++i) 
   for (int j = 0; j != 100; ++j)
     X[j+i*100] = 0;
}

into a single memset of 10000 bytes.  This series of changes
should also be helpful for other nested loop scenarios as well.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123079 91177308-0d34-0410-b5e6-96231b3b80d8
2011-01-08 19:59:06 +00:00
..
ADCE
ArgumentPromotion
BlockPlacement
BranchFolding
CodeExtractor
CodeGenPrepare revert r122164, I'm going to go with a different approach. 2010-12-19 04:23:03 +00:00
ConstantMerge
ConstProp test/Transforms/ConstProp/logicaltest.ll: FileCheck-ize. 2010-12-29 03:58:56 +00:00
CorrelatedValuePropagation Fix PR8790, another instance where unreachable code can cause instruction simplification to fail, 2010-12-15 00:55:35 +00:00
DeadArgElim Preserve debug info attached with call instruction while eliminating dead argument. 2010-04-30 20:23:54 +00:00
DeadStoreElimination Fix PR8728, a miscompilation I recently introduced. When optimizing 2010-12-06 01:48:06 +00:00
EarlyCSE Duncan deftly points out that readnone functions aren't 2011-01-03 23:38:13 +00:00
FunctionAttrs Make ModRefBehavior a lattice. Use this to clean up AliasAnalysis 2010-11-10 01:02:18 +00:00
GlobalDCE
GlobalOpt fix a globalopt crash on two Adobe-C++ testcases that the recent 2011-01-01 22:31:46 +00:00
GVN Give GVN back the ability to perform simple conditional propagation on conditional branch values. 2010-12-21 23:54:34 +00:00
IndVarSimplify
Inline when eliding a byval copy due to inlining a readonly function, we have 2010-12-20 08:10:40 +00:00
InstCombine Fix a bug in r123034 (trying to sext/zext non-integers) and clean up a little. 2011-01-08 10:51:36 +00:00
InstSimplify Revert commit 122654 at the request of Chris, who reckons that instsimplify 2011-01-01 20:08:02 +00:00
Internalize
IPConstantProp
JumpThreading Teach jump threading to "look through" a select when the branch direction of a terminator depends on it. 2010-12-15 09:51:20 +00:00
LCSSA
LICM Enhance LICM to promote alias sets whose pointers themselves are stored, 2010-12-19 05:57:25 +00:00
LoopDeletion
LoopIdiom Teach loop-idiom to turn a loop containing a memset into a larger memset 2011-01-04 07:46:33 +00:00
LoopRotate When loop rotation happens, it is *very* common for the duplicated condbr 2011-01-08 19:59:06 +00:00
LoopSimplify Fix PR8702 by not having LoopSimplify claim to preserve LCSSA form. As described 2011-01-02 13:38:21 +00:00
LoopStrengthReduce
LoopUnroll
LoopUnswitch
LowerAtomic
LowerInvoke
LowerSetJmp
LowerSwitch
Mem2Reg
MemCpyOpt start using irbuilder to make mem intrinsics in a few passes. 2010-12-26 22:57:41 +00:00
MergeFunc
PartialSpecialize
PruneEH
Reassociate
ScalarRepl
SCCP
SimplifyCFG SimplifyCFG: Ranges can be larger than 64 bits. Fixes Release-selfhost build. 2010-12-17 10:48:14 +00:00
SimplifyLibCalls Revert r64460. strtol and friends cannot be marked readonly, even with 2010-12-17 01:09:43 +00:00
Sink
SRETPromotion
StripSymbols
TailCallElim
TailDup