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authorRichard Barton <richard.barton@arm.com>2012-04-24 11:13:20 +0000
committerRichard Barton <richard.barton@arm.com>2012-04-24 11:13:20 +0000
commitf4478f99dd63503bf0f0e763bc6d684e738bfe3d (patch)
treed139a1a78eea92c8b5c50d095a24b62d452bbb7f
parentd1a79136e33afd7069edb4c73d31af3fafb840a2 (diff)
Refactor Thumb ITState handling in ARM Disassembler to more efficiently use its vector
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155439 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--lib/Target/ARM/Disassembler/ARMDisassembler.cpp100
1 files changed, 69 insertions, 31 deletions
diff --git a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 912935db17a..81a61fe9646 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -24,12 +24,66 @@
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"
+#include <vector>
using namespace llvm;
typedef MCDisassembler::DecodeStatus DecodeStatus;
namespace {
+ // Handles the condition code status of instructions in IT blocks
+ class ITStatus
+ {
+ public:
+ // Returns the condition code for instruction in IT block
+ unsigned getITCC() {
+ unsigned CC = ARMCC::AL;
+ if (instrInITBlock())
+ CC = ITStates.back();
+ return CC;
+ }
+
+ // Advances the IT block state to the next T or E
+ void advanceITState() {
+ ITStates.pop_back();
+ }
+
+ // Returns true if the current instruction is in an IT block
+ bool instrInITBlock() {
+ return !ITStates.empty();
+ }
+
+ // Returns true if current instruction is the last instruction in an IT block
+ bool instrLastInITBlock() {
+ return ITStates.size() == 1;
+ }
+
+ // Called when decoding an IT instruction. Sets the IT state for the following
+ // instructions that for the IT block. Firstcond and Mask correspond to the
+ // fields in the IT instruction encoding.
+ void setITState(char Firstcond, char Mask) {
+ // (3 - the number of trailing zeros) is the number of then / else.
+ unsigned CondBit0 = Mask >> 4 & 1;
+ unsigned NumTZ = CountTrailingZeros_32(Mask);
+ unsigned char CCBits = static_cast<unsigned char>(Firstcond & 0xf);
+ assert(NumTZ <= 3 && "Invalid IT mask!");
+ // push condition codes onto the stack the correct order for the pops
+ for (unsigned Pos = NumTZ+1; Pos <= 3; ++Pos) {
+ bool T = ((Mask >> Pos) & 1) == CondBit0;
+ if (T)
+ ITStates.push_back(CCBits);
+ else
+ ITStates.push_back(CCBits ^ 1);
+ }
+ ITStates.push_back(CCBits);
+ }
+
+ private:
+ std::vector<unsigned char> ITStates;
+ };
+}
+
+namespace {
/// ARMDisassembler - ARM disassembler for all ARM platforms.
class ARMDisassembler : public MCDisassembler {
public:
@@ -78,7 +132,7 @@ public:
/// getEDInfo - See MCDisassembler.
const EDInstInfo *getEDInfo() const;
private:
- mutable std::vector<unsigned> ITBlock;
+ mutable ITStatus ITBlock;
DecodeStatus AddThumbPredicate(MCInst&) const;
void UpdateThumbVFPPredicate(MCInst&) const;
};
@@ -612,7 +666,7 @@ ThumbDisassembler::AddThumbPredicate(MCInst &MI) const {
case ARM::tSETEND:
// Some instructions (mostly conditional branches) are not
// allowed in IT blocks.
- if (!ITBlock.empty())
+ if (ITBlock.instrInITBlock())
S = SoftFail;
else
return Success;
@@ -623,7 +677,7 @@ ThumbDisassembler::AddThumbPredicate(MCInst &MI) const {
case ARM::t2TBH:
// Some instructions (mostly unconditional branches) can
// only appears at the end of, or outside of, an IT.
- if (ITBlock.size() > 1)
+ if (ITBlock.instrInITBlock() && !ITBlock.instrLastInITBlock())
S = SoftFail;
break;
default:
@@ -633,13 +687,11 @@ ThumbDisassembler::AddThumbPredicate(MCInst &MI) const {
// If we're in an IT block, base the predicate on that. Otherwise,
// assume a predicate of AL.
unsigned CC;
- if (!ITBlock.empty()) {
- CC = ITBlock.back();
- if (CC == 0xF)
- CC = ARMCC::AL;
- ITBlock.pop_back();
- } else
+ CC = ITBlock.getITCC();
+ if (CC == 0xF)
CC = ARMCC::AL;
+ if (ITBlock.instrInITBlock())
+ ITBlock.advanceITState();
const MCOperandInfo *OpInfo = ARMInsts[MI.getOpcode()].OpInfo;
unsigned short NumOps = ARMInsts[MI.getOpcode()].NumOperands;
@@ -674,11 +726,9 @@ ThumbDisassembler::AddThumbPredicate(MCInst &MI) const {
// context as a post-pass.
void ThumbDisassembler::UpdateThumbVFPPredicate(MCInst &MI) const {
unsigned CC;
- if (!ITBlock.empty()) {
- CC = ITBlock.back();
- ITBlock.pop_back();
- } else
- CC = ARMCC::AL;
+ CC = ITBlock.getITCC();
+ if (ITBlock.instrInITBlock())
+ ITBlock.advanceITState();
const MCOperandInfo *OpInfo = ARMInsts[MI.getOpcode()].OpInfo;
MCInst::iterator I = MI.begin();
@@ -726,7 +776,7 @@ DecodeStatus ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
result = decodeThumbSBitInstruction16(MI, insn16, Address, this, STI);
if (result) {
Size = 2;
- bool InITBlock = !ITBlock.empty();
+ bool InITBlock = ITBlock.instrInITBlock();
Check(result, AddThumbPredicate(MI));
AddThumb1SBit(MI, InITBlock);
return result;
@@ -739,7 +789,7 @@ DecodeStatus ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
// Nested IT blocks are UNPREDICTABLE. Must be checked before we add
// the Thumb predicate.
- if (MI.getOpcode() == ARM::t2IT && !ITBlock.empty())
+ if (MI.getOpcode() == ARM::t2IT && ITBlock.instrInITBlock())
result = MCDisassembler::SoftFail;
Check(result, AddThumbPredicate(MI));
@@ -749,21 +799,9 @@ DecodeStatus ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
// to the subsequent instructions.
if (MI.getOpcode() == ARM::t2IT) {
- // (3 - the number of trailing zeros) is the number of then / else.
- unsigned firstcond = MI.getOperand(0).getImm();
+ unsigned Firstcond = MI.getOperand(0).getImm();
unsigned Mask = MI.getOperand(1).getImm();
- unsigned CondBit0 = Mask >> 4 & 1;
- unsigned NumTZ = CountTrailingZeros_32(Mask);
- assert(NumTZ <= 3 && "Invalid IT mask!");
- for (unsigned Pos = 3, e = NumTZ; Pos > e; --Pos) {
- bool T = ((Mask >> Pos) & 1) == CondBit0;
- if (T)
- ITBlock.insert(ITBlock.begin(), firstcond);
- else
- ITBlock.insert(ITBlock.begin(), firstcond ^ 1);
- }
-
- ITBlock.push_back(firstcond);
+ ITBlock.setITState(Firstcond, Mask);
}
return result;
@@ -783,7 +821,7 @@ DecodeStatus ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
result = decodeThumbInstruction32(MI, insn32, Address, this, STI);
if (result != MCDisassembler::Fail) {
Size = 4;
- bool InITBlock = ITBlock.size();
+ bool InITBlock = ITBlock.instrInITBlock();
Check(result, AddThumbPredicate(MI));
AddThumb1SBit(MI, InITBlock);
return result;