mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-21 03:29:40 +00:00
(familiar) function: int _strlen(const char *str) { int len = 0; while (*str++) len++; return len; } And transforming it to use a ulong induction variable, because the type of the pointer index was left as a constant long. This is obviously very bad. The fix is to shrink long constants in getelementptr instructions to intptr_t, making the indvars pass insert a uint induction variable, which is much more efficient. Here's the before code for this function: int %_strlen(sbyte* %str) { entry: %tmp.13 = load sbyte* %str ; <sbyte> [#uses=1] %tmp.24 = seteq sbyte %tmp.13, 0 ; <bool> [#uses=1] br bool %tmp.24, label %loopexit, label %no_exit no_exit: ; preds = %entry, %no_exit *** %indvar = phi uint [ %indvar.next, %no_exit ], [ 0, %entry ] ; <uint> [#uses=2] *** %indvar = phi ulong [ %indvar.next, %no_exit ], [ 0, %entry ] ; <ulong> [#uses=2] %indvar1 = cast ulong %indvar to uint ; <uint> [#uses=1] %inc.02.sum = add uint %indvar1, 1 ; <uint> [#uses=1] %inc.0.0 = getelementptr sbyte* %str, uint %inc.02.sum ; <sbyte*> [#uses=1] %tmp.1 = load sbyte* %inc.0.0 ; <sbyte> [#uses=1] %tmp.2 = seteq sbyte %tmp.1, 0 ; <bool> [#uses=1] %indvar.next = add ulong %indvar, 1 ; <ulong> [#uses=1] %indvar.next = add uint %indvar, 1 ; <uint> [#uses=1] br bool %tmp.2, label %loopexit.loopexit, label %no_exit loopexit.loopexit: ; preds = %no_exit %indvar = cast uint %indvar to int ; <int> [#uses=1] %inc.1 = add int %indvar, 1 ; <int> [#uses=1] ret int %inc.1 loopexit: ; preds = %entry ret int 0 } Here's the after code: int %_strlen(sbyte* %str) { entry: %inc.02 = getelementptr sbyte* %str, uint 1 ; <sbyte*> [#uses=1] %tmp.13 = load sbyte* %str ; <sbyte> [#uses=1] %tmp.24 = seteq sbyte %tmp.13, 0 ; <bool> [#uses=1] br bool %tmp.24, label %loopexit, label %no_exit no_exit: ; preds = %entry, %no_exit *** %indvar = phi uint [ %indvar.next, %no_exit ], [ 0, %entry ] ; <uint> [#uses=3] %indvar = cast uint %indvar to int ; <int> [#uses=1] %inc.0.0 = getelementptr sbyte* %inc.02, uint %indvar ; <sbyte*> [#uses=1] %inc.1 = add int %indvar, 1 ; <int> [#uses=1] %tmp.1 = load sbyte* %inc.0.0 ; <sbyte> [#uses=1] %tmp.2 = seteq sbyte %tmp.1, 0 ; <bool> [#uses=1] %indvar.next = add uint %indvar, 1 ; <uint> [#uses=1] br bool %tmp.2, label %loopexit, label %no_exit loopexit: ; preds = %entry, %no_exit %len.0.1 = phi int [ 0, %entry ], [ %inc.1, %no_exit ] ; <int> [#uses=1] ret int %len.0.1 } git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13016 91177308-0d34-0410-b5e6-96231b3b80d8 |
||
---|---|---|
.. | ||
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 |