diff options
Diffstat (limited to 'chapter22/src/main/java/com/seaofnodes')
| -rw-r--r-- | chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java | 9 | ||||
| -rw-r--r-- | chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java | 34 |
2 files changed, 27 insertions, 16 deletions
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java b/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java index 91553f38..86cbfe97 100644 --- a/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java +++ b/chapter22/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java @@ -421,6 +421,15 @@ public class CodeGen { // Debugging helper public Node f(int idx) { return _stop.find(idx); } + + String printCFG() { + if( _cfg==null ) return "no CFG"; + SB sb = new SB(); + for( CFGNode cfg : _cfg ) + IRPrinter.printLine(cfg,sb); + return sb.toString(); + } + public static void print_as_hex(Encoding enc) { for (byte b : enc._bits.toByteArray()) { System.out.print(String.format("%02X", b)); diff --git a/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java b/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java index c822a73e..d7057839 100644 --- a/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java +++ b/chapter22/src/main/java/com/seaofnodes/simple/codegen/Encoding.java @@ -256,7 +256,7 @@ public class Encoding { ? (bb.nOuts()>1 || !(bb.cfg0() instanceof IfNode) ) // Forwards jump. If all the blocks, in RPO order, to our // target are empty, we will fall in and not need a jump. - : !isEmptyBackwardsScan(rpo,next); + : !backwardsEmptyScan(rpo,next); if( needJump ) { CFGNode jmp = _code._mach.jump(); jmp._ltree = bb._ltree; @@ -277,12 +277,18 @@ public class Encoding { // bld` is true, the `fld < bld` must be false, or else both directions // exit the loop... and the IF test would not be in the loop. - // true to exit a loop usually, keep true if taking an empty backwards branch - if( tld < bld ) return emptyBackBlock(f,bld); + // true to exit a loop usually (and false falls into Yet Another Loop + // Block), invert if false is taking an empty backwards branch. + if( tld < bld ) return forwardsEmptyScan(f,bld); // false to exit a loop, normally invert to true (except empty back) - if( fld < bld ) return !emptyBackBlock(t,bld); + if( fld < bld ) return !forwardsEmptyScan(t,bld); // Not exiting the loop; staying at this depth (or going deeper loop). + + // Jump/true to an empty backwards block + if( forwardsEmptyScan(t,bld) ) return false; + if( forwardsEmptyScan(f,bld) ) return true ; + // Fall/false into a full block, Jump/true to an empty block. if( f.nOuts()>1 && t.nOuts()==1 ) return false; if( t.nOuts()>1 && f.nOuts()==1 ) return true ; @@ -290,13 +296,17 @@ public class Encoding { return t._pre > f._pre; } - private static boolean emptyBackBlock( CFGNode c, int bld ) { - return c.loopDepth()==bld && c.nOuts()==1 && c.uctrl() instanceof LoopNode; + // Do we continue forwards from 'c' to the Loop back edge, without doing + // anything else? Then this branch can directly jump to the loop head. + private static boolean forwardsEmptyScan( CFGNode c, int bld ) { + if( c.nOuts()!=1 || c.loopDepth()!=bld ) return false; + return c.uctrl() instanceof RegionNode cfg && + (cfg instanceof LoopNode || forwardsEmptyScan(cfg,bld)); } // Is the CFG from "next" to the end empty? This means jumping to "next" // will naturally fall into the end. - private static boolean isEmptyBackwardsScan(Ary<CFGNode> rpo, CFGNode next) { + private static boolean backwardsEmptyScan(Ary<CFGNode> rpo, CFGNode next) { for( int i=rpo._len-1; rpo.at(i)!=next; i-- ) if( rpo.at(i).nOuts()!=1 ) return false; @@ -449,7 +459,7 @@ public class Encoding { // A series of libc/external calls that Simple can link against in a JIT. // Since no runtime in the JVM process, using magic numbers for the CPU // emulators to pick up on. - public static int SENTINAL_CALLOC = -2; + public static int SENTINAL_CALLOC = -4; void patchGlobalRelocations() { for( Node src : _externals.keySet() ) { @@ -462,12 +472,4 @@ public class Encoding { ((RIPRelSize)src).patch(this, start, _opLen[src._nid], target - start); } } - - String printCFG() { - if( _code._cfg==null ) return "no CFG"; - SB sb = new SB(); - for( CFGNode cfg : _code._cfg ) - IRPrinter.printLine(cfg,sb); - return sb.toString(); - } } |