From 52d15ae92dd0be68b0432a47e69c15fe29f663bf Mon Sep 17 00:00:00 2001
From: Hojun-Cho <ghwns6743@gmail.com>
Date: Tue, 2 Jun 2026 22:33:06 +0900
Subject: [PATCH] w6a/asm: Jcc if-pyramid -> switch (Wave-2 structural)

Fold the 13-arm Jcc else-if pyramid in encode() to a single switch (op)
with the terminal else (isjcc=false) as the empty-label default case.
Pure op->cc value mapping, so a switch expresses it exactly.

Not byte-id-neutral (if-chain -> switch dispatch changes the asm). The
ladder<->switch byte-emission equivalence is pinned by 991_w6a_ww, whose
corpus (wwdump/w6l/w6a main.s) emits all 13 Jcc conditions, and was
independently reproduced at landing (all 13 mnemonics assemble
byte-identical C-w6a vs w6a_ww).

Regenerates the w6a combined.ww amalgamation (Jcc region only).
---
 selfhost/cmd/w6a/asm.ww           | 30 ++++++++++++++++--------------
 selfhost/cmd/w6a/main.combined.ww | 30 ++++++++++++++++--------------
 2 files changed, 32 insertions(+), 28 deletions(-)

diff --git a/selfhost/cmd/w6a/asm.ww b/selfhost/cmd/w6a/asm.ww
index cf9d6953..aebaab45 100644
--- a/selfhost/cmd/w6a/asm.ww
+++ b/selfhost/cmd/w6a/asm.ww
@@ -804,20 +804,22 @@ export fn encode(a: *asm_) i32 = {
 		// Conditional jumps. 0x0F + cc + rel32.
 		let cc: u8 = 0u8;
 		let isjcc: bool = true;
-		if (op == A_JE)       { cc = 132u8; }	// 0x84
-		else { if (op == A_JZ)  { cc = 132u8; }
-		else { if (op == A_JNE) { cc = 133u8; }
-		else { if (op == A_JNZ) { cc = 133u8; }
-		else { if (op == A_JL)  { cc = 140u8; }
-		else { if (op == A_JLE) { cc = 142u8; }
-		else { if (op == A_JG)  { cc = 143u8; }
-		else { if (op == A_JGE) { cc = 141u8; }
-		else { if (op == A_JB)  { cc = 130u8; }
-		else { if (op == A_JBE) { cc = 134u8; }
-		else { if (op == A_JA)  { cc = 135u8; }
-		else { if (op == A_JAE) { cc = 131u8; }
-		else { if (op == A_JP)  { cc = 138u8; }	// 0x8A, UCOMISD unordered (#97)
-		else { isjcc = false; };};};};};};};};};};};};};
+		switch (op) {
+		case A_JE:  cc = 132u8;	// 0x84
+		case A_JZ:  cc = 132u8;
+		case A_JNE: cc = 133u8;
+		case A_JNZ: cc = 133u8;
+		case A_JL:  cc = 140u8;
+		case A_JLE: cc = 142u8;
+		case A_JG:  cc = 143u8;
+		case A_JGE: cc = 141u8;
+		case A_JB:  cc = 130u8;
+		case A_JBE: cc = 134u8;
+		case A_JA:  cc = 135u8;
+		case A_JAE: cc = 131u8;
+		case A_JP:  cc = 138u8;	// 0x8A, UCOMISD unordered (#97)
+		case:       isjcc = false;
+		};
 		if (isjcc) {
 			emitbyte(a, 15u8);
 			emitbyte(a, cc);
diff --git a/selfhost/cmd/w6a/main.combined.ww b/selfhost/cmd/w6a/main.combined.ww
index bdc12b93..2a910a0c 100644
--- a/selfhost/cmd/w6a/main.combined.ww
+++ b/selfhost/cmd/w6a/main.combined.ww
@@ -4526,20 +4526,22 @@ export fn encode(a: *asm_) i32 = {
 		// Conditional jumps. 0x0F + cc + rel32.
 		let cc: u8 = 0u8;
 		let isjcc: bool = true;
-		if (op == A_JE)       { cc = 132u8; }	// 0x84
-		else { if (op == A_JZ)  { cc = 132u8; }
-		else { if (op == A_JNE) { cc = 133u8; }
-		else { if (op == A_JNZ) { cc = 133u8; }
-		else { if (op == A_JL)  { cc = 140u8; }
-		else { if (op == A_JLE) { cc = 142u8; }
-		else { if (op == A_JG)  { cc = 143u8; }
-		else { if (op == A_JGE) { cc = 141u8; }
-		else { if (op == A_JB)  { cc = 130u8; }
-		else { if (op == A_JBE) { cc = 134u8; }
-		else { if (op == A_JA)  { cc = 135u8; }
-		else { if (op == A_JAE) { cc = 131u8; }
-		else { if (op == A_JP)  { cc = 138u8; }	// 0x8A, UCOMISD unordered (#97)
-		else { isjcc = false; };};};};};};};};};};};};};
+		switch (op) {
+		case A_JE:  cc = 132u8;	// 0x84
+		case A_JZ:  cc = 132u8;
+		case A_JNE: cc = 133u8;
+		case A_JNZ: cc = 133u8;
+		case A_JL:  cc = 140u8;
+		case A_JLE: cc = 142u8;
+		case A_JG:  cc = 143u8;
+		case A_JGE: cc = 141u8;
+		case A_JB:  cc = 130u8;
+		case A_JBE: cc = 134u8;
+		case A_JA:  cc = 135u8;
+		case A_JAE: cc = 131u8;
+		case A_JP:  cc = 138u8;	// 0x8A, UCOMISD unordered (#97)
+		case:       isjcc = false;
+		};
 		if (isjcc) {
 			emitbyte(a, 15u8);
 			emitbyte(a, cc);