KVM: emulate: cleanup decode_modrm

Remove the if conditional - that will help us avoid
an "else initialize to 0" Also, rearrange operators
for slightly better code.

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

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 000fc73..94f5f8b 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1066,19 +1066,17 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
                        struct operand *op)
 {
        u8 sib;
-       int index_reg = 0, base_reg = 0, scale;
+       int index_reg, base_reg, scale;
        int rc = X86EMUL_CONTINUE;
        ulong modrm_ea = 0;
 
-       if (ctxt->rex_prefix) {
-               ctxt->modrm_reg = (ctxt->rex_prefix & 4) << 1;  /* REX.R */
-               index_reg = (ctxt->rex_prefix & 2) << 2; /* REX.X */
-               ctxt->modrm_rm = base_reg = (ctxt->rex_prefix & 1) << 3; /* REG.B */
-       }
+       ctxt->modrm_reg = ((ctxt->rex_prefix << 1) & 8); /* REX.R */
+       index_reg = (ctxt->rex_prefix << 2) & 8; /* REX.X */
+       base_reg = (ctxt->rex_prefix << 3) & 8; /* REX.B */
 
-       ctxt->modrm_mod |= (ctxt->modrm & 0xc0) >> 6;
+       ctxt->modrm_mod = (ctxt->modrm & 0xc0) >> 6;
        ctxt->modrm_reg |= (ctxt->modrm & 0x38) >> 3;
-       ctxt->modrm_rm |= (ctxt->modrm & 0x07);
+       ctxt->modrm_rm = base_reg | (ctxt->modrm & 0x07);
        ctxt->modrm_seg = VCPU_SREG_DS;
 
        if (ctxt->modrm_mod == 3 || (ctxt->d & NoMod)) {