From 5b035613ee8e95e318f4747ac415587c7c26d9ac Mon Sep 17 00:00:00 2001
From: Zachary Snow <zach@zachjs.com>
Date: Tue, 8 Aug 2023 22:25:39 -0400
Subject: [PATCH] constant fold || and &&

---
 CHANGELOG.md                     |  4 ++++
 src/Convert/ExprUtils.hs         | 22 +++++++++++++++++++++
 test/basic/simplify_binop.sv     | 33 +++++++++++++++++++++++++++++++-
 test/basic/simplify_binop.sv.pat |  2 ++
 4 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 test/basic/simplify_binop.sv.pat

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 878577a..8ea7d50 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,10 @@
 * Fixed certain non-ANSI style port declarations being incorrectly reported as
   incompatible
 
+### Other Enhancements
+
+* Added constant folding for `||` and `&&`
+
 ## v0.0.11
 
 ### New Features
diff --git a/src/Convert/ExprUtils.hs b/src/Convert/ExprUtils.hs
index 63cd783..2fcb37f 100644
--- a/src/Convert/ExprUtils.hs
+++ b/src/Convert/ExprUtils.hs
@@ -161,6 +161,9 @@ simplifyBinOp op (Number n) (ConvertedUU sz v k) | isCmpOp op =
 simplifyBinOp op (ConvertedUU sz v k) (Number n) | isCmpOp op =
     simplifyBinOp op (uuExtend sz v k) (Number n)
 
+simplifyBinOp op (Number n) e | op == LogAnd || op == LogOr =
+    simplifyLogAndOr op n e
+
 simplifyBinOp op e1 e2 =
     case (e1, e2) of
         (Dec    x, Dec    y) -> constantFold orig op   x    y
@@ -327,3 +330,22 @@ simplifyRange (e1, e2) = (simplify e1, simplify e2)
 
 simplifyDimensions :: [Range] -> [Range]
 simplifyDimensions = map simplifyRange
+
+-- TODO: extend this to other logical binary operators
+simplifyLogAndOr :: BinOp -> Number -> Expr -> Expr
+simplifyLogAndOr op n1 (Number n2) =
+    case (numberToInteger n1, numberToInteger n2) of
+        (Just v, _) | (v /= 0) == isOr -> bool isOr
+        (_, Just v) | (v /= 0) == isOr -> bool isOr
+        (Nothing, _) -> boolUnknown
+        (_, Nothing) -> boolUnknown
+        _ -> bool $ not isOr
+    where
+        isOr = op == LogOr
+        boolUnknown = Number $ Based 1 False Binary 0 1
+simplifyLogAndOr op n e =
+    case numberToInteger n of
+        Just v | (v /= 0) == isOr -> bool isOr
+        Just _ -> UniOp LogNot $ UniOp LogNot e
+        Nothing -> BinOp op (Number n) e
+    where isOr = op == LogOr
diff --git a/test/basic/simplify_binop.sv b/test/basic/simplify_binop.sv
index 665fa5a..fd66091 100644
--- a/test/basic/simplify_binop.sv
+++ b/test/basic/simplify_binop.sv
@@ -1,3 +1,34 @@
+`define TEST(expr) initial begin : \blk``expr \
+    localparam X = expr; \
+    localparam [63:0] Y = X; \
+    $display(`"expr %b %b %b`", expr, X, Y); \
+end
+
+`define TEST_LOGOP(op) \
+    `TEST(0``op``0) \
+    `TEST(0``op``1) \
+    `TEST(0``op``1'bx) \
+    `TEST(0``op``P) \
+    `TEST(0``op``Q) \
+    `TEST(0``op``R) \
+    `TEST(1``op``0) \
+    `TEST(1``op``1) \
+    `TEST(1``op``1'bx) \
+    `TEST(1``op``P) \
+    `TEST(1``op``Q) \
+    `TEST(1``op``R) \
+    `TEST(1'bx``op``0) \
+    `TEST(1'bx``op``1) \
+    `TEST(1'bx``op``1'bx) \
+    `TEST(1'bx``op``P) \
+    `TEST(1'bx``op``Q) \
+    `TEST(1'bx``op``R)
+
 module top;
-    initial $display("%b", (12'hb03 - 12'hb07) + 12'hb10);
+    `TEST((12'hb03-12'hb07)+12'hb10)
+    parameter P = 0;
+    parameter Q = 1;
+    parameter R = 1'bx;
+    `TEST_LOGOP(||)
+    `TEST_LOGOP(&&)
 endmodule
diff --git a/test/basic/simplify_binop.sv.pat b/test/basic/simplify_binop.sv.pat
new file mode 100644
index 0000000..e39ce50
--- /dev/null
+++ b/test/basic/simplify_binop.sv.pat
@@ -0,0 +1,2 @@
+reject || 1
+reject && 1