From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 21 Nov 2024 12:01:45 +0000 (+0100)
Subject: target/i386: use shr to load high-byte registers into T0/T1
X-Git-Tag: v10.0.0-rc0~86^2~20
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ef682b08a0b52f4e6d9d790e26291f146e05734a;p=thirdparty%2Fqemu.git

target/i386: use shr to load high-byte registers into T0/T1

Using a sextract or extract operation is only necessary if a
sign or zero extended value is needed.  If not, a shift is
enough.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/target/i386/tcg/emit.c.inc b/target/i386/tcg/emit.c.inc
index 5c11542935..c4cc5f48d8 100644
--- a/target/i386/tcg/emit.c.inc
+++ b/target/i386/tcg/emit.c.inc
@@ -286,24 +286,25 @@ static void gen_load(DisasContext *s, X86DecodedInsn *decode, int opn, TCGv v)
                 gen_op_ld_v(s, op->ot, v, s->A0);
             }
 
-        } else if (op->ot == MO_8 && byte_reg_is_xH(s, op->n)) {
-            if (v == s->T0 && decode->e.special == X86_SPECIAL_SExtT0) {
-                tcg_gen_sextract_tl(v, cpu_regs[op->n - 4], 8, 8);
-            } else {
-                tcg_gen_extract_tl(v, cpu_regs[op->n - 4], 8, 8);
-            }
-
         } else if (op->ot < MO_TL && v == s->T0 &&
                    (decode->e.special == X86_SPECIAL_SExtT0 ||
                     decode->e.special == X86_SPECIAL_ZExtT0)) {
-            if (decode->e.special == X86_SPECIAL_SExtT0) {
-                tcg_gen_ext_tl(v, cpu_regs[op->n], op->ot | MO_SIGN);
+            if (op->ot == MO_8 && byte_reg_is_xH(s, op->n)) {
+                if (decode->e.special == X86_SPECIAL_SExtT0) {
+                    tcg_gen_sextract_tl(v, cpu_regs[op->n - 4], 8, 8);
+                } else {
+                    tcg_gen_extract_tl(v, cpu_regs[op->n - 4], 8, 8);
+                }
             } else {
-                tcg_gen_ext_tl(v, cpu_regs[op->n], op->ot);
+                if (decode->e.special == X86_SPECIAL_SExtT0) {
+                    tcg_gen_ext_tl(v, cpu_regs[op->n], op->ot | MO_SIGN);
+                } else {
+                    tcg_gen_ext_tl(v, cpu_regs[op->n], op->ot);
+                }
             }
 
         } else {
-            tcg_gen_mov_tl(v, cpu_regs[op->n]);
+            gen_op_mov_v_reg(s, op->ot, v, op->n);
         }
         break;
     case X86_OP_IMM:
diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
index 834aea1e59..dbc9d637c4 100644
--- a/target/i386/tcg/translate.c
+++ b/target/i386/tcg/translate.c
@@ -486,7 +486,7 @@ static inline
 void gen_op_mov_v_reg(DisasContext *s, MemOp ot, TCGv t0, int reg)
 {
     if (ot == MO_8 && byte_reg_is_xH(s, reg)) {
-        tcg_gen_extract_tl(t0, cpu_regs[reg - 4], 8, 8);
+        tcg_gen_shri_tl(t0, cpu_regs[reg - 4], 8);
     } else {
         tcg_gen_mov_tl(t0, cpu_regs[reg]);
     }