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Simulate and disasm NOP on ARM

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R=ulan@chromium.org

Review URL: https://chromiumcodereview.appspot.com/11116011
Patch from JF Bastien <jfb@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12737 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
ulan@chromium.org 2012-10-15 15:42:09 +00:00
parent 02490829dd
commit a86e897924
4 changed files with 14 additions and 3 deletions
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10
src/arm/assembler-arm.cc
View File

@ -2440,15 +2440,19 @@ void Assembler::vsqrt(const DwVfpRegister dst,
// Pseudo instructions.
void Assembler::nop(int type) {
// This is mov rx, rx.
ASSERT(0 <= type && type <= 14); // mov pc, pc is not a nop.
// ARMv6{K/T2} and v7 have an actual NOP instruction but it serializes
// some of the CPU's pipeline and has to issue. Older ARM chips simply used
// MOV Rx, Rx as NOP and it performs better even in newer CPUs.
// We therefore use MOV Rx, Rx, even on newer CPUs, and use Rx to encode
// a type.
ASSERT(0 <= type && type <= 14); // mov pc, pc isn't a nop.
emit(al | 13*B21 | type*B12 | type);
}
bool Assembler::IsNop(Instr instr, int type) {
ASSERT(0 <= type && type <= 14); // mov pc, pc isn't a nop.
// Check for mov rx, rx where x = type.
ASSERT(0 <= type && type <= 14); // mov pc, pc is not a nop.
return instr == (al | 13*B21 | type*B12 | type);
}

3
src/arm/constants-arm.h
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@ -687,6 +687,9 @@ class Instruction {
&& (Bit(20) == 0)
&& ((Bit(7) == 0)); }
// Test for a nop instruction, which falls under type 1.
inline bool IsNopType1() const { return Bits(24, 0) == 0x0120F000; }
// Test for a stop instruction.
inline bool IsStop() const {
return (TypeValue() == 7) && (Bit(24) == 1) && (SvcValue() >= kStopCode);

2
src/arm/disasm-arm.cc
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@ -830,6 +830,8 @@ void Decoder::DecodeType01(Instruction* instr) {
} else {
Unknown(instr); // not used by V8
}
} else if ((type == 1) && instr->IsNopType1()) {
Format(instr, "nop'cond");
} else {
switch (instr->OpcodeField()) {
case AND: {

2
src/arm/simulator-arm.cc
View File

@ -2183,6 +2183,8 @@ void Simulator::DecodeType01(Instruction* instr) {
PrintF("%08x\n", instr->InstructionBits());
UNIMPLEMENTED();
}
} else if ((type == 1) && instr->IsNopType1()) {
// NOP.
} else {
int rd = instr->RdValue();
int rn = instr->RnValue();