From 0d62818db7f16bb47692e916dfb9115d63ee77d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20Balv=C3=ADn?= <opensource@petrbalvin.org>
Date: Thu, 27 Aug 2026 17:35:25 +0200
Subject: [PATCH] feat(amd64): encode legacy SSE binaries, imm8 shuffles and
 MOVQ xmm moves

---
 .idea/.gitignore      | 10 ++++++++++
 .idea/gasm-devkit.iml |  9 +++++++++
 .idea/modules.xml     |  8 ++++++++
 .idea/vcs.xml         |  6 ++++++
 asm/encode_test.go    | 26 ++++++++++++++++++++++++++
 asm/instrs.go         | 25 +++++++++++++++++++++++++
 6 files changed, 84 insertions(+)
 create mode 100644 .idea/.gitignore
 create mode 100644 .idea/gasm-devkit.iml
 create mode 100644 .idea/modules.xml
 create mode 100644 .idea/vcs.xml

diff --git a/.idea/.gitignore b/.idea/.gitignore
new file mode 100644
index 0000000..30cf57e
--- /dev/null
+++ b/.idea/.gitignore
@@ -0,0 +1,10 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Ignored default folder with query files
+/queries/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml
diff --git a/.idea/gasm-devkit.iml b/.idea/gasm-devkit.iml
new file mode 100644
index 0000000..7c421e3
--- /dev/null
+++ b/.idea/gasm-devkit.iml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="WEB_MODULE" version="4">
+  <component name="GoModuleSettings" enabled="true" />
+  <component name="NewModuleRootManager">
+    <content url="file://$MODULE_DIR$" />
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>
\ No newline at end of file
diff --git a/.idea/modules.xml b/.idea/modules.xml
new file mode 100644
index 0000000..fa14643
--- /dev/null
+++ b/.idea/modules.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/gasm-devkit.iml" filepath="$PROJECT_DIR$/.idea/gasm-devkit.iml" />
+    </modules>
+  </component>
+</project>
\ No newline at end of file
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
new file mode 100644
index 0000000..35eb1dd
--- /dev/null
+++ b/.idea/vcs.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>
\ No newline at end of file
diff --git a/asm/encode_test.go b/asm/encode_test.go
index cec3aa2..c041a75 100644
--- a/asm/encode_test.go
+++ b/asm/encode_test.go
@@ -369,3 +369,29 @@ func TestSSEShuffleGroundTruth(t *testing.T) {
 		}
 	}
 }
+
+// TestMOVQXMMGroundTruth pins the SSE2 packed-quadword move encodings:
+// loads and register moves on F3 0F 7E, stores on 66 0F D6 — the forms
+// the GPR-move fallback silently corrupted.
+func TestMOVQXMMGroundTruth(t *testing.T) {
+	cases := []struct {
+		name string
+		mnem string
+		ops  []Operand
+		want string
+	}{
+		{"MOVQ (DI),X0", "MOVQ", []Operand{Ptr(DI, 0, 8), vreg(t, "X0")}, "f30f7e07"},
+		{"MOVQ X1,X2", "MOVQ", []Operand{vreg(t, "X1"), vreg(t, "X2")}, "f30f7ed1"},
+		{"MOVQ X0,(DI)", "MOVQ", []Operand{vreg(t, "X0"), Ptr(DI, 0, 8)}, "660fd607"},
+	}
+	for _, c := range cases {
+		code, err := Encode(c.mnem, c.ops...)
+		if err != nil {
+			t.Errorf("%s: %v", c.name, err)
+			continue
+		}
+		if got := fmt.Sprintf("%x", code); got != c.want {
+			t.Errorf("%s = %s, want %s", c.name, got, c.want)
+		}
+	}
+}
diff --git a/asm/instrs.go b/asm/instrs.go
index 6237f38..b963ddf 100644
--- a/asm/instrs.go
+++ b/asm/instrs.go
@@ -48,6 +48,31 @@ func (e *enc) encodeMov(ops []Operand, size int) error {
 	}
 	src, dst := ops[0], ops[1]
 
+	// MOVQ with an XMM operand is the SSE2 packed-quadword move, NOT a
+	// GPR move: mem→xmm and xmm↔xmm encode as F3 0F 7E (reg = dst),
+	// xmm→mem as 66 0F D6 (rm = xmm).  A GPR-move fallback would
+	// silently emit REX.W 8B with the wrong operand meaning.
+	_, srcVec := vecReg(src)
+	dstReg, dstVec := vecReg(dst)
+	if srcVec || dstVec {
+		if dstVec {
+			i := &instr{prefix: 0xF3, opcode: []byte{0x0F, 0x7E}, modrm: -1, sib: -1}
+			if err := setRM(i, dstReg, src, 8); err != nil {
+				return err
+			}
+			return e.emit(i)
+		}
+		srcXMM, srcIsXMM := src.(Reg)
+		if !srcIsXMM || !srcXMM.isVec() {
+			return fmt.Errorf("MOVQ: store needs an XMM source")
+		}
+		i := &instr{prefix: 0x66, opcode: []byte{0x0F, 0xD6}, modrm: -1, sib: -1}
+		if err := setRM(i, srcXMM, dst, 8); err != nil {
+			return err
+		}
+		return e.emit(i)
+	}
+
 	dstReg, dstIsReg := dst.(Reg)
 	switch src := src.(type) {
 	case Reg: