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Simplify drreg state restoration code. #4976

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merged 4 commits into from
Jun 30, 2021
Merged

Simplify drreg state restoration code. #4976

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b11e7a3
iX: Simply drreg state restoration code.
abhinav92003 Jun 29, 2021
10e6194
Separate out is-meta-instr condition to outer if.
abhinav92003 Jun 29, 2021
3703f29
Grammar fix.
abhinav92003 Jun 30, 2021
4c316dc
Merge branch 'master' into iX-simplify-drreg-state-restore
abhinav92003 Jun 30, 2021
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113 changes: 54 additions & 59 deletions ext/drreg/drreg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2107,80 +2107,26 @@ drreg_event_restore_state_with_ilist(void *drcontext, bool restore_memory,
last_opcode = instr_get_opcode(inst);
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}

bool app_gpr_restored_now = false;
bool app_aflags_restored_now = false;
bool app_aflags_written_to_reg_now = false;
/* Update book-keeping for gpr/aflags spill slot or aflags spill reg. */
if (!instr_is_app(inst) &&
is_our_spill_or_restore(drcontext, inst, &spill, &reg, &slot, &offs)) {
if (spill) {
/* Slot used in current instr may have a previous spilled gpr/aflags
* value that may already have been restored. Forget that.
*/
spill_slot_to_reg[slot] = DR_REG_NULL;
if (aflags_spill_reg == reg) {
ASSERT(!gpr_native[GPR_IDX(aflags_spill_reg)],
"reg with aflags cannot be native");
spill_slot_to_reg[slot] = AFLAGS_ALIAS_REG;
} else if (gpr_native[GPR_IDX(reg)]) {
spill_slot_to_reg[slot] = reg;
} else {
LOG(drcontext, DR_LOG_ALL, 3,
"%s @" PFX ": ignoring tool spill of non-native value.\n",
__FUNCTION__, pc);
}
} else {
if (spill_slot_to_reg[slot] == AFLAGS_ALIAS_REG) {
aflags_spill_reg = reg;
app_aflags_written_to_reg_now = true;
} else if (spill_slot_to_reg[slot] == reg) {
gpr_native[GPR_IDX(reg)] = true;
app_gpr_restored_now = true;
} else {
LOG(drcontext, DR_LOG_ALL, 3,
"%s @" PFX ": ignoring tool restore of non-native value\n",
__FUNCTION__, pc);
}
}
} else if (!instr_is_app(inst) &&
instr_get_opcode(inst) == IF_X86_ELSE(OP_lahf, OP_mrs)) {
if (aflags_native) {
#ifdef X86
aflags_spill_reg = DR_REG_XAX;
#else
aflags_spill_reg = opnd_get_reg(instr_get_dst(inst, 0));
#endif
app_aflags_written_to_reg_now = true;
}
} else if (!instr_is_app(inst) &&
instr_get_opcode(inst) == IF_X86_ELSE(OP_sahf, OP_msr)) {
if (aflags_spill_reg ==
IF_X86_ELSE(DR_REG_XAX, opnd_get_reg(instr_get_src(inst, 0)))) {
aflags_native = true;
app_aflags_restored_now = true;
}
}

/* Mark gprs/aflags as containing native or non-native value based on whether
* the current instr is an app or tool write, respectively. An example of the
* latter is a restore for a spilled tool value, which may happen in the
* multi-phase nested reservation case.
* If the current instr is a tool write that restores an app value (as tracked
* by the various *_now bools), we skip marking the gpr/aflags as non-native.
* Later we check whether the current instr restores the native app value for
* any gpr/aflags, and if it does we mark the written gpr/aflags as native.
*/
for (int i = 0; i < instr_num_dsts(inst); i++) {
opnd_t opnd = instr_get_dst(inst, i);
if (opnd_is_reg(opnd) && reg_is_gpr(opnd_get_reg(opnd))) {
reg_id_t resized_reg = reg_to_pointer_sized(opnd_get_reg(opnd));
if (resized_reg == aflags_spill_reg && !app_aflags_written_to_reg_now) {
if (resized_reg == aflags_spill_reg) {
/* reg does not contain aflags anymore. */
aflags_spill_reg = DR_REG_NULL;
}
if (instr_is_app(inst)) {
/* App instr wrote reg value. Spill slot value not valid anymore. */
gpr_native[GPR_IDX(resized_reg)] = true;
forget_existing_spill_slot_use(spill_slot_to_reg, resized_reg);
} else if (!app_gpr_restored_now) {
} else {
/* Tool wrote to reg. Not native anymore. */
gpr_native[GPR_IDX(resized_reg)] = false;
}
Expand All @@ -2194,11 +2140,60 @@ drreg_event_restore_state_with_ilist(void *drcontext, bool restore_memory,
aflags_native = true;
forget_existing_spill_slot_use(spill_slot_to_reg, AFLAGS_ALIAS_REG);
aflags_spill_reg = DR_REG_NULL;
} else if (!app_aflags_restored_now) {
} else {
/* Tool wrote aflags. Not native anymore. */
aflags_native = false;
}
}

/* Update book-keeping for gpr/aflags spill slot and aflags spill reg. Mark
* as native the gprs/aflags that were restored. All spills/restores are meta
* instrs.
*/
if (!instr_is_app(inst)) {
if (is_our_spill_or_restore(drcontext, inst, &spill, &reg, &slot, &offs)) {
if (spill) {
/* Slot used in current instr may have a previous spilled gpr/aflags
* value that may already have been restored. Forget that.
*/
spill_slot_to_reg[slot] = DR_REG_NULL;
if (aflags_spill_reg == reg) {
ASSERT(!gpr_native[GPR_IDX(aflags_spill_reg)],
"reg with aflags cannot be native");
spill_slot_to_reg[slot] = AFLAGS_ALIAS_REG;
} else if (gpr_native[GPR_IDX(reg)]) {
spill_slot_to_reg[slot] = reg;
} else {
LOG(drcontext, DR_LOG_ALL, 3,
"%s @" PFX ": ignoring tool spill of non-native value.\n",
__FUNCTION__, pc);
}
} else {
if (spill_slot_to_reg[slot] == AFLAGS_ALIAS_REG) {
aflags_spill_reg = reg;
} else if (spill_slot_to_reg[slot] == reg) {
gpr_native[GPR_IDX(reg)] = true;
} else {
LOG(drcontext, DR_LOG_ALL, 3,
"%s @" PFX ": ignoring tool restore of non-native value\n",
__FUNCTION__, pc);
}
}
} else if (instr_get_opcode(inst) == IF_X86_ELSE(OP_lahf, OP_mrs)) {
if (aflags_native) {
#ifdef X86
aflags_spill_reg = DR_REG_XAX;
#else
aflags_spill_reg = opnd_get_reg(instr_get_dst(inst, 0));
#endif
}
} else if (instr_get_opcode(inst) == IF_X86_ELSE(OP_sahf, OP_msr)) {
if (aflags_spill_reg ==
IF_X86_ELSE(DR_REG_XAX, opnd_get_reg(instr_get_src(inst, 0)))) {
aflags_native = true;
}
}
}
}
ASSERT(inst != NULL, "fault pc is beyond the given ilist");
if (!aflags_native) {
Expand Down