From 190e5aa70862f40ba96b7dc7add3f11a8143c66f Mon Sep 17 00:00:00 2001
From: Martin <martin.brain@diffblue.com>
Date: Fri, 15 Sep 2017 04:04:20 +0100
Subject: Make floating-point comparison operators chainable (#1101)

Floating-point comparison operators are chainable according to the standard.
---
 src/theory/fp/kinds                  |  8 +++---
 src/theory/fp/theory_fp_rewriter.cpp | 48 ++++++++++++++++++++++++++++++++----
 2 files changed, 47 insertions(+), 9 deletions(-)

(limited to 'src/theory/fp')

diff --git a/src/theory/fp/kinds b/src/theory/fp/kinds
index 983d5aa5c..a1b28d885 100644
--- a/src/theory/fp/kinds
+++ b/src/theory/fp/kinds
@@ -94,16 +94,16 @@ operator FLOATINGPOINT_MAX 2 "floating-point maximum"
 typerule FLOATINGPOINT_MAX   ::CVC4::theory::fp::FloatingPointOperationTypeRule
 
 
-operator FLOATINGPOINT_LEQ 2 "floating-point less than or equal"
+operator FLOATINGPOINT_LEQ 2: "floating-point less than or equal"
 typerule FLOATINGPOINT_LEQ   ::CVC4::theory::fp::FloatingPointTestTypeRule
 
-operator FLOATINGPOINT_LT 2 "floating-point less than"
+operator FLOATINGPOINT_LT 2: "floating-point less than"
 typerule FLOATINGPOINT_LT   ::CVC4::theory::fp::FloatingPointTestTypeRule
 
-operator FLOATINGPOINT_GEQ 2 "floating-point greater than or equal"
+operator FLOATINGPOINT_GEQ 2: "floating-point greater than or equal"
 typerule FLOATINGPOINT_GEQ   ::CVC4::theory::fp::FloatingPointTestTypeRule
 
-operator FLOATINGPOINT_GT 2 "floating-point greater than"
+operator FLOATINGPOINT_GT 2: "floating-point greater than"
 typerule FLOATINGPOINT_GT   ::CVC4::theory::fp::FloatingPointTestTypeRule
 
 
diff --git a/src/theory/fp/theory_fp_rewriter.cpp b/src/theory/fp/theory_fp_rewriter.cpp
index ba4bf9228..747aaeac6 100644
--- a/src/theory/fp/theory_fp_rewriter.cpp
+++ b/src/theory/fp/theory_fp_rewriter.cpp
@@ -37,6 +37,16 @@ namespace fp {
 
 namespace rewrite {
   /** Rewrite rules **/
+  template <RewriteFunction first, RewriteFunction second>
+  RewriteResponse then (TNode node, bool isPreRewrite) {
+    RewriteResponse result(first(node, isPreRewrite));
+
+    if (result.status == REWRITE_DONE) {
+      return second(result.node, isPreRewrite);
+    } else {
+      return result;
+    }
+  }
 
   RewriteResponse notFP (TNode node, bool) {
     Unreachable("non floating-point kind (%d) in floating point rewrite?",node.getKind());
@@ -67,6 +77,34 @@ namespace rewrite {
     return RewriteResponse(REWRITE_DONE, addition);
   }
 
+  RewriteResponse breakChain (TNode node, bool isPreRewrite) {
+    Assert(isPreRewrite);  // Should be run first
+
+    Kind k = node.getKind();
+    Assert(k == kind::FLOATINGPOINT_EQ ||
+	   k == kind::FLOATINGPOINT_GEQ ||
+	   k == kind::FLOATINGPOINT_LEQ ||
+	   k == kind::FLOATINGPOINT_GT ||
+	   k == kind::FLOATINGPOINT_LT);
+
+
+    size_t children = node.getNumChildren();
+    if (children > 2) {
+
+      NodeBuilder<> conjunction(kind::AND);
+
+      for (size_t i = 0; i < children - 1; ++i) {
+	for (size_t j = i + 1; j < children; ++j) {
+	  conjunction << NodeManager::currentNM()->mkNode(k, node[i], node[j]);
+	}
+      }
+      return RewriteResponse(REWRITE_AGAIN_FULL, conjunction);
+
+    } else {
+      return RewriteResponse(REWRITE_DONE, node);
+    }
+  }
+
 
   /* Implies (fp.eq x x) --> (not (isNaN x))
    */
@@ -314,11 +352,11 @@ RewriteFunction TheoryFpRewriter::postRewriteTable[kind::LAST_KIND];
     preRewriteTable[kind::FLOATINGPOINT_MAX] = rewrite::compactMinMax;
 
     /******** Comparisons ********/
-    preRewriteTable[kind::FLOATINGPOINT_EQ] = rewrite::ieeeEqToEq;
-    preRewriteTable[kind::FLOATINGPOINT_LEQ] = rewrite::identity;
-    preRewriteTable[kind::FLOATINGPOINT_LT] = rewrite::identity;
-    preRewriteTable[kind::FLOATINGPOINT_GEQ] = rewrite::geqToleq;
-    preRewriteTable[kind::FLOATINGPOINT_GT] = rewrite::gtTolt;
+    preRewriteTable[kind::FLOATINGPOINT_EQ] = rewrite::then<rewrite::breakChain,rewrite::ieeeEqToEq>;
+    preRewriteTable[kind::FLOATINGPOINT_LEQ] = rewrite::breakChain;
+    preRewriteTable[kind::FLOATINGPOINT_LT] = rewrite::breakChain;
+    preRewriteTable[kind::FLOATINGPOINT_GEQ] = rewrite::then<rewrite::breakChain,rewrite::geqToleq>;
+    preRewriteTable[kind::FLOATINGPOINT_GT] = rewrite::then<rewrite::breakChain,rewrite::gtTolt>;
 
     /******** Classifications ********/
     preRewriteTable[kind::FLOATINGPOINT_ISN] = rewrite::identity;
-- 
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