mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-10-03 08:55:51 +00:00
de62192843
e.g.
define i32 @t1(i32 %c, i32 %x) nounwind {
%t1 = icmp eq i32 %c, 0
%t2 = lshr i32 %x, 18
%t3 = select i1 %t1, i32 %t2, i32 %x
ret i32 %t3
}
was turned into
define i32 @t2(i32 %c, i32 %x) nounwind {
%t1 = icmp eq i32 %c, 0
%t2 = select i1 %t1, i32 18, i32 0
%t3 = lshr i32 %x, %t2
ret i32 %t3
}
For most targets, that means materializing two constants and then a select. e.g. On x86-64
movl %esi, %eax
shrl $18, %eax
testl %edi, %edi
cmovne %esi, %eax
ret
=>
xorl %eax, %eax
testl %edi, %edi
movl $18, %ecx
cmovne %eax, %ecx
movl %esi, %eax
shrl %cl, %eax
ret
Also, the optimizer and codegen can reason about shl / and / add, etc. by a constant. This optimization will hinder optimizations using ComputeMaskedBits.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68142 91177308-0d34-0410-b5e6-96231b3b80d8
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| .. | ||
| ADCE | ||
| ArgumentPromotion | ||
| BlockPlacement | ||
| BranchFolding | ||
| CodeExtractor | ||
| CodeGenPrepare | ||
| CondProp | ||
| ConstantMerge | ||
| ConstProp | ||
| DeadArgElim | ||
| DeadStoreElimination | ||
| FunctionAttrs | ||
| GlobalDCE | ||
| GlobalOpt | ||
| GVN | ||
| GVNPRE | ||
| IndMemRem | ||
| IndVarSimplify | ||
| Inline | ||
| InstCombine | ||
| Internalize | ||
| IPConstantProp | ||
| JumpThreading | ||
| LCSSA | ||
| LICM | ||
| LoopDeletion | ||
| LoopIndexSplit | ||
| LoopRotate | ||
| LoopSimplify | ||
| LoopStrengthReduce | ||
| LoopUnroll | ||
| LoopUnswitch | ||
| LowerInvoke | ||
| LowerSetJmp | ||
| LowerSwitch | ||
| Mem2Reg | ||
| MemCpyOpt | ||
| MergeFunc | ||
| PredicateSimplifier | ||
| PruneEH | ||
| RaiseAllocations | ||
| Reassociate | ||
| ScalarRepl | ||
| SCCP | ||
| SimplifyCFG | ||
| SimplifyLibCalls | ||
| SRETPromotion | ||
| StripSymbols | ||
| TailCallElim | ||
| TailDup | ||