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Op1 (RHS) is a constant, so putting it on the LHS makes us churn through visitICmp an extra time to canonicalize it: INSTCOMBINE ITERATION #1 on cmpnot IC: ADDING: 3 instrs to worklist IC: Visiting: %notx = xor i8 %x, -1 IC: Visiting: %cmp = icmp sgt i8 %notx, 42 IC: Old = %cmp = icmp sgt i8 %notx, 42 New = <badref> = icmp sgt i8 -43, %x IC: ADD: %cmp = icmp sgt i8 -43, %x IC: ERASE %1 = icmp sgt i8 %notx, 42 IC: ADD: %notx = xor i8 %x, -1 IC: DCE: %notx = xor i8 %x, -1 IC: ERASE %notx = xor i8 %x, -1 IC: Visiting: %cmp = icmp sgt i8 -43, %x IC: Mod = %cmp = icmp sgt i8 -43, %x New = %cmp = icmp slt i8 %x, -43 IC: ADD: %cmp = icmp slt i8 %x, -43 IC: Visiting: %cmp = icmp slt i8 %x, -43 IC: Visiting: ret i1 %cmp If we create the swapped ICmp directly, we go faster: INSTCOMBINE ITERATION #1 on cmpnot IC: ADDING: 3 instrs to worklist IC: Visiting: %notx = xor i8 %x, -1 IC: Visiting: %cmp = icmp sgt i8 %notx, 42 IC: Old = %cmp = icmp sgt i8 %notx, 42 New = <badref> = icmp slt i8 %x, -43 IC: ADD: %cmp = icmp slt i8 %x, -43 IC: ERASE %1 = icmp sgt i8 %notx, 42 IC: ADD: %notx = xor i8 %x, -1 IC: DCE: %notx = xor i8 %x, -1 IC: ERASE %notx = xor i8 %x, -1 IC: Visiting: %cmp = icmp slt i8 %x, -43 IC: Visiting: ret i1 %cmp git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304558 91177308-0d34-0410-b5e6-96231b3b80d8
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the documentation provided in docs/ for further assistance with LLVM, and in particular docs/GettingStarted.rst for getting started with LLVM and docs/README.txt for an overview of LLVM's documentation setup. If you are writing a package for LLVM, see docs/Packaging.rst for our suggestions.