1 /* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "Dalvik.h" 18 #include "vm/compiler/CompilerInternals.h" 19 #include "ArmLIR.h" 20 21 /* 22 * Identify unconditional branches that jump to the immediate successor of the 23 * branch itself. 24 */ applyRedundantBranchElimination(CompilationUnit * cUnit)25static void applyRedundantBranchElimination(CompilationUnit *cUnit) 26 { 27 ArmLIR *thisLIR; 28 29 for (thisLIR = (ArmLIR *) cUnit->firstLIRInsn; 30 thisLIR != (ArmLIR *) cUnit->lastLIRInsn; 31 thisLIR = NEXT_LIR(thisLIR)) { 32 33 /* Branch to the next instruction */ 34 if (thisLIR->opcode == kThumbBUncond) { 35 ArmLIR *nextLIR = thisLIR; 36 37 while (true) { 38 nextLIR = NEXT_LIR(nextLIR); 39 40 /* 41 * Is the branch target the next instruction? 42 */ 43 if (nextLIR == (ArmLIR *) thisLIR->generic.target) { 44 thisLIR->flags.isNop = true; 45 break; 46 } 47 48 /* 49 * Found real useful stuff between the branch and the target. 50 * Need to explicitly check the lastLIRInsn here since with 51 * method-based JIT the branch might be the last real 52 * instruction. 53 */ 54 if (!isPseudoOpcode(nextLIR->opcode) || 55 (nextLIR = (ArmLIR *) cUnit->lastLIRInsn)) 56 break; 57 } 58 } 59 } 60 } 61 dvmCompilerApplyGlobalOptimizations(CompilationUnit * cUnit)62void dvmCompilerApplyGlobalOptimizations(CompilationUnit *cUnit) 63 { 64 applyRedundantBranchElimination(cUnit); 65 } 66