From dd907c2d86eaaad0910e7bfe3f0d25e5caf8bdf7 Mon Sep 17 00:00:00 2001 From: Hsiang-Ying Fu <66062782+fuhsnn@users.noreply.github.com> Date: Sat, 26 Sep 2026 06:35:22 +0800 Subject: Extend and backport SubNode peephole (#254) * Extend and backport SubNode peephole * Add tests * Restrict subtraction zero peepholes to integer operands Require resolved integer mode in chapter 25 so zero subtraction preserves floating-point signed zero. Keep nonnumeric operands in the graph for subtraction diagnostics. Add signed-zero coverage from chapter 12 and null-subtraction diagnostics from chapter 22. Confirmed the regressions fail on the original PR. Full Make suites pass in chapters 4-25 (5462 tests), including fresh chapter 25 sys.o compilation. --------- Co-authored-by: Cliff Click --- .../main/java/com/seaofnodes/simple/node/SubNode.java | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'chapter13/src/main/java/com/seaofnodes') diff --git a/chapter13/src/main/java/com/seaofnodes/simple/node/SubNode.java b/chapter13/src/main/java/com/seaofnodes/simple/node/SubNode.java index 4b860c37..4ae302f0 100644 --- a/chapter13/src/main/java/com/seaofnodes/simple/node/SubNode.java +++ b/chapter13/src/main/java/com/seaofnodes/simple/node/SubNode.java @@ -39,14 +39,24 @@ public class SubNode extends Node { @Override public Node idealize() { + Node lhs = in(1); + Node rhs = in(2); + Type t1 = lhs._type; + Type t2 = rhs._type; + + // Keep invalid operands for type checking. + if( t1 instanceof TypeInteger x && t2 instanceof TypeInteger y ) { + if( y.isConstant() && y.value()==0 ) return lhs; + if( x.isConstant() && x.value()==0 ) return new MinusNode(rhs); + } // x - (-y) is x+y - if( in(2) instanceof MinusNode minus ) - return new AddNode(in(1),minus.in(1)); + if( rhs instanceof MinusNode minus ) + return new AddNode(lhs,minus.in(1)); // (-x) - y is -(x+y) - if( in(1) instanceof MinusNode minus ) - return new MinusNode(new AddNode(minus.in(1),in(2)).peephole()); + if( lhs instanceof MinusNode minus ) + return new MinusNode(new AddNode(minus.in(1),rhs).peephole()); return null; } -- cgit v1.2.3