diff options
Diffstat (limited to 'compiler/optimizing/dead_code_elimination.h')
| -rw-r--r-- | compiler/optimizing/dead_code_elimination.h | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/compiler/optimizing/dead_code_elimination.h b/compiler/optimizing/dead_code_elimination.h index b91006be0d..ddd01f7103 100644 --- a/compiler/optimizing/dead_code_elimination.h +++ b/compiler/optimizing/dead_code_elimination.h @@ -46,6 +46,31 @@ class HDeadCodeElimination : public HOptimization { bool RemoveDeadBlocks(bool force_recomputation = false, bool force_loop_recomputation = false); void RemoveDeadInstructions(); bool SimplifyAlwaysThrows(); + // Simplify the pattern: + // + // B1 B2 ... + // goto goto goto + // \ | / + // \ | / + // B3 + // i1 = phi(input, input) + // (i2 = condition on i1) + // if i1 (or i2) + // / \ + // / \ + // B4 B5 + // + // Into: + // + // B1 B2 ... + // | | | + // B4 B5 B? + // + // Note that individual edges can be redirected (for example B2->B3 + // can be redirected as B2->B5) without applying this optimization + // to other incoming edges. + // + // Note that we rely on the dead code elimination to get rid of B3. bool SimplifyIfs(); void ConnectSuccessiveBlocks(); // Updates the graph flags related to instructions (e.g. HasSIMD()) since we may have eliminated @@ -75,6 +100,28 @@ class HDeadCodeElimination : public HOptimization { // instructions. bool RemoveUnneededTries(); + // Adds a phi in `block`, if `block` and its dominator have the same (or opposite) condition. + // For example it turns: + // if(cond) + // / \ + // B1 B2 + // \ / + // if(cond) + // / \ + // B3 B4 + // + // into: + // if(cond) + // / \ + // B1 B2 + // \ / + // if(Phi(1, 0)) + // / \ + // B3 B4 + // + // Following this, SimplifyIfs is able to connect B1->B3 and B2->B4 effectively skipping an if. + void MaybeAddPhi(HBasicBlock* block); + DISALLOW_COPY_AND_ASSIGN(HDeadCodeElimination); }; |