write_rm_multi implementation for uimm (ruby#148)

kddnewton · Feb 11, 2022 · a5443b8 · a5443b8
1 parent 6def931
commit a5443b8
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Showing 2 changed files with 45 additions and 1 deletion.
diff --git a/yjit/src/asm/x86_64/mod.rs b/yjit/src/asm/x86_64/mod.rs
@@ -674,7 +674,7 @@ fn write_rm(cb: &mut CodeBlock, sz_pref: bool, rex_w: bool, r_opnd: X86Opnd, rm_
 
     // Add the operand-size prefix, if needed
     if sz_pref {
-        cb.write_byte(0x66)
+        cb.write_byte(0x66);
     }
 
     // Add the REX prefix, if needed
@@ -822,6 +822,7 @@ fn write_rm_multi(cb: &mut CodeBlock, op_mem_reg8: u8, op_mem_reg_pref: u8, op_r
         X86Opnd::Reg(reg) => assert!(reg.num_bits == opnd_size),
         X86Opnd::Mem(mem) => assert!(mem.num_bits == opnd_size),
         X86Opnd::Imm(imm) => assert!(imm.num_bits <= opnd_size),
+        X86Opnd::UImm(uimm) => assert!(uimm.num_bits <= opnd_size),
         _ => ()
     };
 
@@ -867,6 +868,30 @@ fn write_rm_multi(cb: &mut CodeBlock, op_mem_reg8: u8, op_mem_reg_pref: u8, op_r
                 panic!("immediate value too large");
             }
         },
+        // R/M + UImm
+        (_, X86Opnd::UImm(uimm)) => {
+            let num_bits = sig_imm_size(uimm.value.try_into().unwrap());
+
+            if num_bits <= 8 {
+                // 8-bit immediate
+
+                if opnd_size == 8 {
+                    write_rm(cb, false, false, X86Opnd::None, opnd0, op_ext_imm, 1, &[op_mem_imm8]);
+                } else {
+                    write_rm(cb, sz_pref, rex_w, X86Opnd::None, opnd0, op_ext_imm, 1, &[op_mem_imm_sml]);
+                }
+
+                cb.write_int(uimm.value, 8);
+            } else if num_bits <= 32 {
+                // 32-bit immediate
+
+                assert!(num_bits <= opnd_size);
+                write_rm(cb, sz_pref, rex_w, X86Opnd::None, opnd0, op_ext_imm, 1, &[op_mem_imm_lrg]);
+                cb.write_int(uimm.value, if opnd_size > 32 { 32 } else { opnd_size.into() });
+            } else {
+                panic!("immediate value too large");
+            }
+        },
         _ => unreachable!()
     };
 }

diff --git a/yjit/src/asm/x86_64/tests.rs b/yjit/src/asm/x86_64/tests.rs
@@ -40,6 +40,25 @@ fn test_add() {
     check_bytes("81c1ff000000", |cb| add(cb, ECX, imm_opnd(255)));
 }
 
+#[test]
+fn test_add_unsigned() {
+    // ADD r/m8, imm8
+    check_bytes("4180c001", |cb| add(cb, R8B, uimm_opnd(1)));
+    check_bytes("4180c07f", |cb| add(cb, R8B, imm_opnd(i8::MAX.try_into().unwrap())));
+
+    // ADD r/m16, imm16
+    check_bytes("664183c001", |cb| add(cb, R8W, uimm_opnd(1)));
+    check_bytes("664181c0ff7f", |cb| add(cb, R8W, uimm_opnd(i16::MAX.try_into().unwrap())));
+
+    // ADD r/m32, imm32
+    check_bytes("4183c001", |cb| add(cb, R8D, uimm_opnd(1)));
+    check_bytes("4181c0ffffff7f", |cb| add(cb, R8D, uimm_opnd(i32::MAX.try_into().unwrap())));
+
+    // ADD r/m64, imm32
+    check_bytes("4983c001", |cb| add(cb, R8, uimm_opnd(1)));
+    check_bytes("4981c0ffffff7f", |cb| add(cb, R8, uimm_opnd(i32::MAX.try_into().unwrap())));
+}
+
 #[test]
 fn test_and() {
     check_bytes("4421e5", |cb| and(cb, EBP, R12D));