From bcba5075e8767e1c744a10b7ae2ed6f7094185ec Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Sat, 7 Sep 2013 16:43:43 -0400
Subject: [PATCH] Fix ordering of , msg1229.

---
 Changes                                   |  3 ++-
 src/V3AstNodes.h                          |  2 ++
 src/V3Const.cpp                           |  3 ++-
 test_regress/t/t_sys_file_basic.v         | 20 ++++++++++++++++++++
 test_regress/t/t_sys_file_basic_input.dat |  1 +
 5 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/Changes b/Changes
index 9b61e995c..2ef918e40 100644
--- a/Changes
+++ b/Changes
@@ -7,12 +7,13 @@ indicates the contributor was also the author of the fix; Thanks!
 
 ***   Support named function and task arguments. [Chris Randall]
 
+****  Fix ordering of $fgetc, msg1229. [Frederic Requin]
+
 ****  Fix --output-split-cfunc to count internal functions. [Chris Randall]
 
 ****  Fix crash on 32-bit Ubuntu, bug670. [Mark Jackson Pulver]
 
 
-
 * Verilator 3.851 2013-08-15
 
 ***   Fix ordering of clock enables with delayed assigns, bug613. [Jeremy Bennett]
diff --git a/src/V3AstNodes.h b/src/V3AstNodes.h
index c1ed6b917..a93a0bb81 100644
--- a/src/V3AstNodes.h
+++ b/src/V3AstNodes.h
@@ -3378,6 +3378,7 @@ struct AstFEof : public AstNodeUniop {
     virtual bool cleanOut() {return true;} virtual bool cleanLhs() {return true;}
     virtual bool sizeMattersLhs() {return false;}
     virtual int instrCount()	const { return widthInstrs()*16; }
+    virtual bool isPure() const { return false; }	// SPECIAL: $display has 'visual' ordering
     AstNode*	filep() const { return lhsp(); }
 };
 
@@ -3391,6 +3392,7 @@ struct AstFGetC : public AstNodeUniop {
     virtual bool cleanOut() {return false;} virtual bool cleanLhs() {return true;}
     virtual bool sizeMattersLhs() {return false;}
     virtual int instrCount()	const { return widthInstrs()*64; }
+    virtual bool isPure() const { return false; }	// SPECIAL: $display has 'visual' ordering
     AstNode*	filep() const { return lhsp(); }
 };
 
diff --git a/src/V3Const.cpp b/src/V3Const.cpp
index dc785f40d..fbc4a21fe 100644
--- a/src/V3Const.cpp
+++ b/src/V3Const.cpp
@@ -815,9 +815,10 @@ private:
 
     bool varNotReferenced(AstNode* nodep, AstVar* varp, int level=0) {
 	// Return true if varp never referenced under node.
-	// Return false if referenced, or tree too deep to be worth it
+	// Return false if referenced, or tree too deep to be worth it, or side effects
 	if (!nodep) return true;
 	if (level>2) return false;
+	if (nodep->isPure()) return false;  // For example a $fgetc can't be reordered
 	if (nodep->castNodeVarRef() && nodep->castNodeVarRef()->varp()==varp) return false;
 	return (varNotReferenced  (nodep->nextp(),varp,level+1)
 		&& varNotReferenced(nodep->op1p(),varp,level+1)
diff --git a/test_regress/t/t_sys_file_basic.v b/test_regress/t/t_sys_file_basic.v
index cdf2783a3..df8fcda6e 100644
--- a/test_regress/t/t_sys_file_basic.v
+++ b/test_regress/t/t_sys_file_basic.v
@@ -15,6 +15,10 @@ module t;
    reg [16*8:1]	letterz;
    real		r;
 
+   reg [7:0] 	v_a,v_b,v_c,v_d;
+   reg [31:0] 	v_worda;
+   reg [31:0] 	v_wordb;
+
 `ifdef TEST_VERBOSE
  `define verbose 1'b1
 `else
@@ -174,6 +178,22 @@ module t;
 	 if (chars != 1) $stop;
 	 if (letterl != "\n") $stop;
 
+	 // msg1229
+	 v_a = $fgetc(file);
+	 v_b = $fgetc(file);
+	 v_c = $fgetc(file);
+	 v_d = $fgetc(file);
+	 v_worda = { v_d, v_c, v_b, v_a };
+	 if (v_worda != "4321") $stop;
+
+	 v_wordb[7:0]   = $fgetc(file);
+	 v_wordb[15:8]  = $fgetc(file);
+	 v_wordb[23:16] = $fgetc(file);
+	 v_wordb[31:24] = $fgetc(file);
+	 if (v_wordb != "9876") $stop;
+
+	 if ($fgetc(file) != "\n") $stop;
+
 	 $fclose(file);
       end
 
diff --git a/test_regress/t/t_sys_file_basic_input.dat b/test_regress/t/t_sys_file_basic_input.dat
index 0a085c6fb..67437584c 100644
--- a/test_regress/t/t_sys_file_basic_input.dat
+++ b/test_regress/t/t_sys_file_basic_input.dat
@@ -6,3 +6,4 @@ widestuff
 *oa=23 ob=12563
 *d=-236123
 *fredfishblah
+12346789