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40 #include "arch/x86/emulenv.hh"
44 #include "base/logging.hh"
46 using namespace X86ISA
;
48 void EmulEnv::doModRM(const ExtMachInst
& machInst
)
50 assert(machInst
.modRM
.mod
!= 3);
51 //Use the SIB byte for addressing if the modrm byte calls for it.
52 if (machInst
.modRM
.rm
== 4 && machInst
.addrSize
!= 2) {
53 scale
= 1 << machInst
.sib
.scale
;
54 index
= machInst
.sib
.index
| (machInst
.rex
.x
<< 3);
55 base
= machInst
.sib
.base
| (machInst
.rex
.b
<< 3);
56 //In this special case, we don't use a base. The displacement also
57 //changes, but that's managed by the decoder.
58 if (machInst
.sib
.base
== INTREG_RBP
&& machInst
.modRM
.mod
== 0)
60 //In -this- special case, we don't use an index.
61 if (index
== INTREG_RSP
)
64 if (machInst
.addrSize
== 2) {
65 unsigned rm
= machInst
.modRM
.rm
;
73 index
= (rm
% 2) ? INTREG_RDI
: INTREG_RSI
;
93 base
= machInst
.modRM
.rm
| (machInst
.rex
.b
<< 3);
94 if (machInst
.modRM
.mod
== 0 && machInst
.modRM
.rm
== 5) {
95 //Since we need to use a different encoding of this
96 //instruction anyway, just ignore the base in those cases
101 //Figure out what segment to use. This won't be entirely accurate since
102 //the presence of a displacement is supposed to make the instruction
103 //default to the data segment.
104 if ((base
!= INTREG_RBP
&& base
!= INTREG_RSP
) || machInst
.dispSize
) {
105 seg
= SEGMENT_REG_DS
;
106 //Handle any segment override that might have been in the instruction
107 int segFromInst
= machInst
.legacy
.seg
;
109 seg
= (SegmentRegIndex
)(segFromInst
- 1);
111 seg
= SEGMENT_REG_SS
;
115 void EmulEnv::setSeg(const ExtMachInst
& machInst
)
117 seg
= SEGMENT_REG_DS
;
118 //Handle any segment override that might have been in the instruction
119 int segFromInst
= machInst
.legacy
.seg
;
121 seg
= (SegmentRegIndex
)(segFromInst
- 1);