mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-10-31 09:11:13 +00:00
59fdaeeae8
Instead of producing code like this:
Loop:
X = phi 0, X2
...
X2 = X + 1
if (X != N-1) goto Loop
We now generate code that looks like this:
Loop:
X = phi 0, X2
...
X2 = X + 1
if (X2 != N) goto Loop
This has two big advantages:
1. The trip count of the loop is now explicit in the code, allowing
the direct implementation of Loop::getTripCount()
2. This reduces register pressure in the loop, and allows X and X2 to be
put into the same register.
As a consequence of the second point, the code we generate for loops went
from:
.LBB2: # no_exit.1
...
mov %EDI, %ESI
inc %EDI
cmp %ESI, 2
mov %ESI, %EDI
jne .LBB2 # PC rel: no_exit.1
To:
.LBB2: # no_exit.1
...
inc %ESI
cmp %ESI, 3
jne .LBB2 # PC rel: no_exit.1
... which has two fewer moves, and uses one less register.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12961 91177308-0d34-0410-b5e6-96231b3b80d8
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|---|---|---|
| .. | ||
| ADCE.cpp | ||
| BasicBlockPlacement.cpp | ||
| ConstantProp.cpp | ||
| CorrelatedExprs.cpp | ||
| DCE.cpp | ||
| DecomposeMultiDimRefs.cpp | ||
| GCSE.cpp | ||
| IndVarSimplify.cpp | ||
| InstructionCombining.cpp | ||
| LICM.cpp | ||
| Makefile | ||
| PiNodeInsertion.cpp | ||
| PRE.cpp | ||
| Reassociate.cpp | ||
| ScalarReplAggregates.cpp | ||
| SCCP.cpp | ||
| SimplifyCFG.cpp | ||
| SymbolStripping.cpp | ||
| TailDuplication.cpp | ||
| TailRecursionElimination.cpp | ||