From c1c5b10082166c7a091132989ceb8f6e72c9ee9e Mon Sep 17 00:00:00 2001
From: Sylvie <35663410+Rangi42@users.noreply.github.com>
Date: Tue, 10 Dec 2024 21:27:37 -0500
Subject: [PATCH] Deprecate `LDH` with $00-$FF (#1575)

---
 include/asm/rpn.hpp          |  2 +-
 man/rgbasm-old.5             | 17 +++++++++++++++++
 src/asm/parser.y             | 14 ++++++++++++--
 src/asm/rpn.cpp              |  8 ++++++--
 src/link/patch.cpp           |  6 ++++++
 test/asm/deprecated-ldio.err |  8 ++++++++
 6 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/include/asm/rpn.hpp b/include/asm/rpn.hpp
index b5b95ba83..69d7700c3 100644
--- a/include/asm/rpn.hpp
+++ b/include/asm/rpn.hpp
@@ -53,7 +53,7 @@ struct Expression {
 	void makeUnaryOp(RPNCommand op, Expression &&src);
 	void makeBinaryOp(RPNCommand op, Expression &&src1, Expression const &src2);
 
-	void makeCheckHRAM();
+	bool makeCheckHRAM();
 	void makeCheckRST();
 
 	void checkNBit(uint8_t n) const;
diff --git a/man/rgbasm-old.5 b/man/rgbasm-old.5
index 29217ff37..767e51523 100644
--- a/man/rgbasm-old.5
+++ b/man/rgbasm-old.5
@@ -267,6 +267,23 @@ Instead, use
 .Ql LDH [C], A
 and
 .Ql LDH A, [C] .
+.Ss LDH [n8], A and LDH A, [n8]
+Deprecated in 0.9.0.
+.Pp
+.Ql LDH
+used to treat "addresses" from
+.Ad $00
+to
+.Ad $FF
+as if they were the low byte of an address from
+.Ad $FF00
+to
+.Ad $FFFF .
+.Pp
+Instead, use
+.Ql LDH [n16], A
+and
+.Ql LDH A, [n16] .
 .Ss rgbasm -i
 Deprecated in 0.6.0, removed in 0.8.0.
 .Pp
diff --git a/src/asm/parser.y b/src/asm/parser.y
index cb4069093..7a74d7bb1 100644
--- a/src/asm/parser.y
+++ b/src/asm/parser.y
@@ -1949,13 +1949,23 @@ z80_ldd:
 
 z80_ldh:
 	Z80_LDH MODE_A COMMA op_mem_ind {
-		$4.makeCheckHRAM();
+		if ($4.makeCheckHRAM()) {
+			warning(
+			    WARNING_OBSOLETE,
+			    "LDH is deprecated with values from $00 to $FF; use $FF00 to $FFFF\n"
+			);
+		}
 
 		sect_ConstByte(0xF0);
 		sect_RelByte($4, 1);
 	}
 	| Z80_LDH op_mem_ind COMMA MODE_A {
-		$2.makeCheckHRAM();
+		if ($2.makeCheckHRAM()) {
+			warning(
+			    WARNING_OBSOLETE,
+			    "LDH is deprecated with values from $00 to $FF; use $FF00 to $FFFF\n"
+			);
+		}
 
 		sect_ConstByte(0xE0);
 		sect_RelByte($2, 1);
diff --git a/src/asm/rpn.cpp b/src/asm/rpn.cpp
index 126c02483..129922722 100644
--- a/src/asm/rpn.cpp
+++ b/src/asm/rpn.cpp
@@ -568,16 +568,20 @@ void Expression::makeBinaryOp(RPNCommand op, Expression &&src1, Expression const
 	}
 }
 
-void Expression::makeCheckHRAM() {
+bool Expression::makeCheckHRAM() {
 	isSymbol = false;
 	if (!isKnown()) {
 		*reserveSpace(1) = RPN_HRAM;
 	} else if (int32_t val = value(); val >= 0xFF00 && val <= 0xFFFF) {
 		// That range is valid, but only keep the lower byte
 		data = val & 0xFF;
-	} else if (val < 0 || val > 0xFF) {
+	} else if (val >= 0 && val <= 0xFF) {
+		// That range is valid, but deprecated
+		return true;
+	} else {
 		error("Source address $%" PRIx32 " not between $FF00 to $FFFF\n", val);
 	}
+	return false;
 }
 
 void Expression::makeCheckRST() {
diff --git a/src/link/patch.cpp b/src/link/patch.cpp
index a64f1df19..9270782be 100644
--- a/src/link/patch.cpp
+++ b/src/link/patch.cpp
@@ -356,6 +356,12 @@ static int32_t computeRPNExpr(Patch const &patch, std::vector<Symbol> const &fil
 					isError = true;
 				}
 				value = 0;
+			} else if (value >= 0 && value <= 0xFF) {
+				warning(
+				    patch.src,
+				    patch.lineNo,
+				    "LDH is deprecated with values from $00 to $FF; use $FF00 to $FFFF"
+				);
 			}
 			value &= 0xFF;
 			break;
diff --git a/test/asm/deprecated-ldio.err b/test/asm/deprecated-ldio.err
index a1abbe3b8..d9b04081b 100644
--- a/test/asm/deprecated-ldio.err
+++ b/test/asm/deprecated-ldio.err
@@ -1,3 +1,7 @@
+warning: deprecated-ldio.asm(5): [-Wobsolete]
+    LDH is deprecated with values from $00 to $FF; use $FF00 to $FFFF
+warning: deprecated-ldio.asm(6): [-Wobsolete]
+    LDH is deprecated with values from $00 to $FF; use $FF00 to $FFFF
 warning: deprecated-ldio.asm(8): [-Wobsolete]
     LD [C], A is deprecated; use LDH [C], A
 warning: deprecated-ldio.asm(9): [-Wobsolete]
@@ -10,6 +14,10 @@ warning: deprecated-ldio.asm(15): [-Wobsolete]
     LDIO is deprecated; use LDH
 warning: deprecated-ldio.asm(16): [-Wobsolete]
     LDIO is deprecated; use LDH
+warning: deprecated-ldio.asm(20): [-Wobsolete]
+    LDH is deprecated with values from $00 to $FF; use $FF00 to $FFFF
+warning: deprecated-ldio.asm(21): [-Wobsolete]
+    LDH is deprecated with values from $00 to $FF; use $FF00 to $FFFF
 warning: deprecated-ldio.asm(23): [-Wobsolete]
     LD [C], A is deprecated; use LDH [C], A
 warning: deprecated-ldio.asm(24): [-Wobsolete]