feat(asm): add prefetch hint encoding

2026-08-29 10:42:15 +02:00
parent ba4d961b20
commit 6699ebd34f
2 changed files with 60 additions and 0 deletions
@@ -317,3 +317,37 @@ end:
 		t.Errorf("jump-folding mismatch:\n got:  %s\n want: %s", hexBytes(code), hexBytes(want))
 	}
 }
+
+func TestAssemblePrefetch(t *testing.T) {
+	fn := firstText(t, `
+#include "textflag.h"
+TEXT ·pf(SB), NOSPLIT, $0
+	PREFETCHNTA (AX)
+	PREFETCHT0 (BX)
+	PREFETCHT1 8(CX)
+	PREFETCHT2 -1(AX)(R12*1)
+	RET
+`)
+	code, _, err := Assemble(fn)
+	if err != nil {
+		t.Fatalf("Assemble: %v", err)
+	}
+	got := strings.Join(disasm(t, code), "\n")
+	want := strings.Join([]string{
+		"prefetchnta zmmword ptr [rax]",
+		"prefetcht0 zmmword ptr [rbx]",
+		"prefetcht1 zmmword ptr [rcx+0x8]",
+		"prefetcht2 zmmword ptr [rax+r12-0x1]",
+		"ret",
+	}, "\n")
+	if got != want {
+		t.Errorf("prefetch disassembly mismatch:\n got:\n%s\n want:\n%s", got, want)
+	}
+	// Byte-level expectations: 0F 18 with the variant in the reg field.
+	if hex := hexBytes(code[:3]); hex != "0f 18 00" {
+		t.Errorf("PREFETCHNTA bytes: got %s, want 0f 18 00", hex)
+	}
+	if hex := hexBytes(code[3:6]); hex != "0f 18 0b" {
+		t.Errorf("PREFETCHT0 bytes: got %s, want 0f 18 0b", hex)
+	}
+}