fix decoding of rex-prefixed modrm+sib operands selecting index 0b100 and base 0b1010.1.4

for memory operands with a base, index, and displacement either
the wrong base would be selected (register number ignored, so only
`*ax` or `r8*` would be reported), or yaxpeax-x86 would report a
base register is present when it is not (`RegIndexBaseScaleDisp`
when the operand is actually `RegScaleDisp`)

thank you to Evan Johnson for catching and reporting this bug!

also bump crate version to 0.1.4 as this will be immediately tagged and
released.

1 files changed, 12 insertions, 4 deletions

diff --git a/src/long_mode/mod.rs b/src/long_mode/mod.rs
index 363c605..d165e38 100644
--- a/src/long_mode/mod.rs
+++ b/src/long_mode/mod.rs
@@ -5665,20 +5665,28 @@ fn read_sib<T: Iterator<Item=u8>>(bytes_iter: &mut T, instr: &mut Instruction, m
 
                 OperandSpec::DispU32
             } else {
+                instr.modrm_mmm.num |= 0b101;
+
                 if instr.prefixes.rex().x() {
                     instr.sib_index.num = 0b1100;
                     let scale = 1u8 << (sibbyte >> 6);
                     instr.scale = scale;
 
                     if disp == 0 {
-                        OperandSpec::RegIndexBaseScale
+                        if modbits == 0 {
+                            OperandSpec::RegScale
+                        } else {
+                            OperandSpec::RegIndexBaseScale
+                        }
                     } else {
                         instr.disp = disp as i64 as u64;
-                        OperandSpec::RegIndexBaseScaleDisp
+                        if modbits == 0 {
+                            OperandSpec::RegScaleDisp
+                        } else {
+                            OperandSpec::RegIndexBaseScaleDisp
+                        }
                     }
                 } else {
-                    instr.modrm_mmm.num |= 0b101;
-
                     if disp == 0 {
                         OperandSpec::Deref
                     } else {