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S390: Fixed s390 simulation check for underflow in subtraction.

Browse Source 
Clang optimizes away CheckOverflowForIntSub at any opt
level (includes -O1, -O2, -O3) into a false statement,
resulting in incorrect values being returned. As the C++
standard considers overflows to be undefined behaviour,
this is technically correct as compilers can assume that
overflows never occur, but problematic in our case (where
overflows do occur, and a specific result is expected).

This change replaces the original check with a call to a
function that is optimized in a manner that returns correct output.

R=michael_dawson@ca.ibm.com,jyan@ca.ibm.com,mtbrandyberry@ca.ibm.com,joransiu@ca.ibm.com,danno@chromium.org,jkummerow@chromium.org,jochen@chromium.org

BUG=

Review URL: https://codereview.chromium.org/1826043002

Cr-Commit-Position: refs/heads/master@{#35082}
This commit is contained in:
bryleun 2016-03-28 10:12:46 -07:00 committed by Commit bot
parent f5b85cb74c
commit 0d24a0fcfe
2 changed files with 56 additions and 44 deletions
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96
src/s390/simulator-s390.cc
View File

@ -1150,8 +1150,9 @@ bool Simulator::BorrowFrom(int32_t left, int32_t right) {
}
// Calculate V flag value for additions and subtractions.
bool Simulator::OverflowFrom(int32_t alu_out, int32_t left, int32_t right,
bool addition) {
template <typename T1>
bool Simulator::OverflowFromSigned(T1 alu_out, T1 left, T1 right,
bool addition) {
bool overflow;
if (addition) {
// operands have the same sign
@ -1640,12 +1641,11 @@ void Simulator::PrintStopInfo(uint32_t code) {
// (2) Test the result and one of the operands have opposite sign
// (a) No overflow if they don't have opposite sign
// (b) Overflow if opposite
#define CheckOverflowForIntAdd(src1, src2) \
(((src1) ^ (src2)) < 0 ? false : ((((src1) + (src2)) ^ (src1)) < 0))
#define CheckOverflowForIntAdd(src1, src2, type) \
OverflowFromSigned<type>(src1 + src2, src1, src2, true);
// Method for checking overflow on signed subtraction:
#define CheckOverflowForIntSub(src1, src2) \
(((src1 - src2) < src1) != (src2 > 0))
#define CheckOverflowForIntSub(src1, src2, type) \
OverflowFromSigned<type>(src1 - src2, src1, src2, false);
// Method for checking overflow on unsigned addtion
#define CheckOverflowForUIntAdd(src1, src2) \
@ -1686,13 +1686,13 @@ bool Simulator::DecodeTwoByte(Instruction* instr) {
bool isOF = false;
switch (op) {
case AR:
isOF = CheckOverflowForIntAdd(r1_val, r2_val);
isOF = CheckOverflowForIntAdd(r1_val, r2_val, int32_t);
r1_val += r2_val;
SetS390ConditionCode<int32_t>(r1_val, 0);
SetS390OverflowCode(isOF);
break;
case SR:
isOF = CheckOverflowForIntSub(r1_val, r2_val);
isOF = CheckOverflowForIntSub(r1_val, r2_val, int32_t);
r1_val -= r2_val;
SetS390ConditionCode<int32_t>(r1_val, 0);
SetS390OverflowCode(isOF);
@ -2461,13 +2461,13 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
bool isOF = false;
switch (op) {
case AGR:
isOF = CheckOverflowForIntAdd(r1_val, r2_val);
isOF = CheckOverflowForIntAdd(r1_val, r2_val, int64_t);
r1_val += r2_val;
SetS390ConditionCode<int64_t>(r1_val, 0);
SetS390OverflowCode(isOF);
break;
case SGR:
isOF = CheckOverflowForIntSub(r1_val, r2_val);
isOF = CheckOverflowForIntSub(r1_val, r2_val, int64_t);
r1_val -= r2_val;
SetS390ConditionCode<int64_t>(r1_val, 0);
SetS390OverflowCode(isOF);
@ -2497,7 +2497,7 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
int r2 = rreInst->R2Value();
int64_t r1_val = get_register(r1);
int64_t r2_val = static_cast<int64_t>(get_low_register<int32_t>(r2));
bool isOF = CheckOverflowForIntAdd(r1_val, r2_val);
bool isOF = CheckOverflowForIntAdd(r1_val, r2_val, int64_t);
r1_val += r2_val;
SetS390ConditionCode<int64_t>(r1_val, 0);
SetS390OverflowCode(isOF);
@ -2511,7 +2511,7 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
int64_t r1_val = get_register(r1);
int64_t r2_val = static_cast<int64_t>(get_low_register<int32_t>(r2));
bool isOF = false;
isOF = CheckOverflowForIntSub(r1_val, r2_val);
isOF = CheckOverflowForIntSub(r1_val, r2_val, int64_t);
r1_val -= r2_val;
SetS390ConditionCode<int64_t>(r1_val, 0);
SetS390OverflowCode(isOF);
@ -2530,12 +2530,12 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
int32_t r2_val = get_low_register<int32_t>(r2);
int32_t r3_val = get_low_register<int32_t>(r3);
if (ARK == op) {
bool isOF = CheckOverflowForIntAdd(r2_val, r3_val);
bool isOF = CheckOverflowForIntAdd(r2_val, r3_val, int32_t);
SetS390ConditionCode<int32_t>(r2_val + r3_val, 0);
SetS390OverflowCode(isOF);
set_low_register(r1, r2_val + r3_val);
} else if (SRK == op) {
bool isOF = CheckOverflowForIntSub(r2_val, r3_val);
bool isOF = CheckOverflowForIntSub(r2_val, r3_val, int32_t);
SetS390ConditionCode<int32_t>(r2_val - r3_val, 0);
SetS390OverflowCode(isOF);
set_low_register(r1, r2_val - r3_val);
@ -2587,12 +2587,12 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
int64_t r2_val = get_register(r2);
int64_t r3_val = get_register(r3);
if (AGRK == op) {
bool isOF = CheckOverflowForIntAdd(r2_val, r3_val);
bool isOF = CheckOverflowForIntAdd(r2_val, r3_val, int64_t);
SetS390ConditionCode<int64_t>(r2_val + r3_val, 0);
SetS390OverflowCode(isOF);
set_register(r1, r2_val + r3_val);
} else if (SGRK == op) {
bool isOF = CheckOverflowForIntSub(r2_val, r3_val);
bool isOF = CheckOverflowForIntSub(r2_val, r3_val, int64_t);
SetS390ConditionCode<int64_t>(r2_val - r3_val, 0);
SetS390OverflowCode(isOF);
set_register(r1, r2_val - r3_val);
@ -2635,13 +2635,13 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
case AHI:
case MHI: {
RIInstruction* riinst = reinterpret_cast<RIInstruction*>(instr);
int r1 = riinst->R1Value();
int i = riinst->I2Value();
int32_t r1 = riinst->R1Value();
int32_t i = riinst->I2Value();
int32_t r1_val = get_low_register<int32_t>(r1);
bool isOF = false;
switch (op) {
case AHI:
isOF = CheckOverflowForIntAdd(r1_val, i);
isOF = CheckOverflowForIntAdd(r1_val, i, int32_t);
r1_val += i;
break;
case MHI:
@ -2659,13 +2659,13 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
case AGHI:
case MGHI: {
RIInstruction* riinst = reinterpret_cast<RIInstruction*>(instr);
int r1 = riinst->R1Value();
int32_t r1 = riinst->R1Value();
int64_t i = static_cast<int64_t>(riinst->I2Value());
int64_t r1_val = get_register(r1);
bool isOF = false;
switch (op) {
case AGHI:
isOF = CheckOverflowForIntAdd(r1_val, i);
isOF = CheckOverflowForIntAdd(r1_val, i, int64_t);
r1_val += i;
break;
case MGHI:
@ -2752,13 +2752,13 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
bool isOF = false;
switch (op) {
case A:
isOF = CheckOverflowForIntAdd(r1_val, mem_val);
isOF = CheckOverflowForIntAdd(r1_val, mem_val, int32_t);
alu_out = r1_val + mem_val;
SetS390ConditionCode<int32_t>(alu_out, 0);
SetS390OverflowCode(isOF);
break;
case S:
isOF = CheckOverflowForIntSub(r1_val, mem_val);
isOF = CheckOverflowForIntSub(r1_val, mem_val, int32_t);
alu_out = r1_val - mem_val;
SetS390ConditionCode<int32_t>(alu_out, 0);
SetS390OverflowCode(isOF);
@ -2836,14 +2836,14 @@ bool Simulator::DecodeFourByteArithmetic(Instruction* instr) {
int64_t x2_val = (x2 == 0) ? 0 : get_register(x2);
intptr_t d2_val = rxinst->D2Value();
intptr_t addr = b2_val + x2_val + d2_val;
int16_t mem_val = ReadH(addr, instr);
int32_t mem_val = static_cast<int32_t>(ReadH(addr, instr));
int32_t alu_out = 0;
bool isOF = false;
if (AH == op) {
isOF = CheckOverflowForIntAdd(r1_val, mem_val);
isOF = CheckOverflowForIntAdd(r1_val, mem_val, int32_t);
alu_out = r1_val + mem_val;
} else if (SH == op) {
isOF = CheckOverflowForIntSub(r1_val, mem_val);
isOF = CheckOverflowForIntSub(r1_val, mem_val, int32_t);
alu_out = r1_val - mem_val;
} else if (MH == op) {
alu_out = r1_val * mem_val;
@ -4322,14 +4322,14 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
// 32-bit Add
int32_t r2_val = get_low_register<int32_t>(r2);
int32_t imm = rieInst->I6Value();
isOF = CheckOverflowForIntAdd(r2_val, imm);
isOF = CheckOverflowForIntAdd(r2_val, imm, int32_t);
set_low_register(r1, r2_val + imm);
SetS390ConditionCode<int32_t>(r2_val + imm, 0);
} else if (AGHIK == op) {
// 64-bit Add
int64_t r2_val = get_register(r2);
int64_t imm = static_cast<int64_t>(rieInst->I6Value());
isOF = CheckOverflowForIntAdd(r2_val, imm);
isOF = CheckOverflowForIntAdd(r2_val, imm, int64_t);
set_register(r1, r2_val + imm);
SetS390ConditionCode<int64_t>(r2_val + imm, 0);
}
@ -4372,12 +4372,12 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
int32_t mem_val = ReadW(b2_val + x2_val + d2, instr);
bool isOF = false;
if (op == AY) {
isOF = CheckOverflowForIntAdd(alu_out, mem_val);
isOF = CheckOverflowForIntAdd(alu_out, mem_val, int32_t);
alu_out += mem_val;
SetS390ConditionCode<int32_t>(alu_out, 0);
SetS390OverflowCode(isOF);
} else if (op == SY) {
isOF = CheckOverflowForIntSub(alu_out, mem_val);
isOF = CheckOverflowForIntSub(alu_out, mem_val, int32_t);
alu_out -= mem_val;
SetS390ConditionCode<int32_t>(alu_out, 0);
SetS390OverflowCode(isOF);
@ -4407,17 +4407,18 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
int64_t b2_val = (b2 == 0) ? 0 : get_register(b2);
int64_t x2_val = (x2 == 0) ? 0 : get_register(x2);
intptr_t d2_val = rxyInstr->D2Value();
int16_t mem_val = ReadH(b2_val + d2_val + x2_val, instr);
int32_t mem_val =
static_cast<int32_t>(ReadH(b2_val + d2_val + x2_val, instr));
int32_t alu_out = 0;
bool isOF = false;
switch (op) {
case AHY:
alu_out = r1_val + mem_val;
isOF = CheckOverflowForIntAdd(r1_val, mem_val);
isOF = CheckOverflowForIntAdd(r1_val, mem_val, int32_t);
break;
case SHY:
alu_out = r1_val - mem_val;
isOF = CheckOverflowForIntSub(r1_val, mem_val);
isOF = CheckOverflowForIntSub(r1_val, mem_val, int64_t);
break;
default:
UNREACHABLE();
@ -4520,20 +4521,21 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
case AFI: {
// Clobbering Add Word Immediate
RILInstruction* rilInstr = reinterpret_cast<RILInstruction*>(instr);
int r1 = rilInstr->R1Value();
int i2 = rilInstr->I2Value();
int32_t r1 = rilInstr->R1Value();
bool isOF = false;
if (AFI == op) {
// 32-bit Add (Register + 32-bit Immediate)
int32_t r1_val = get_low_register<int32_t>(r1);
isOF = CheckOverflowForIntAdd(r1_val, i2);
int32_t i2 = rilInstr->I2Value();
isOF = CheckOverflowForIntAdd(r1_val, i2, int32_t);
int32_t alu_out = r1_val + i2;
set_low_register(r1, alu_out);
SetS390ConditionCode<int32_t>(alu_out, 0);
} else if (AGFI == op) {
// 64-bit Add (Register + 32-bit Imm)
int64_t r1_val = get_register(r1);
isOF = CheckOverflowForIntAdd(r1_val, i2);
int64_t i2 = static_cast<int64_t>(rilInstr->I2Value());
isOF = CheckOverflowForIntAdd(r1_val, i2, int64_t);
int64_t alu_out = r1_val + i2;
set_register(r1, alu_out);
SetS390ConditionCode<int64_t>(alu_out, 0);
@ -4542,7 +4544,12 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
break;
}
case ASI: {
int8_t i2 = static_cast<int8_t>(siyInstr->I2Value());
// TODO(bcleung): Change all fooInstr->I2Value() to template functions.
// The below static cast to 8 bit and then to 32 bit is necessary
// because siyInstr->I2Value() returns a uint8_t, which a direct
// cast to int32_t could incorrectly interpret.
int8_t i2_8bit = static_cast<int8_t>(siyInstr->I2Value());
int32_t i2 = static_cast<int32_t>(i2_8bit);
int b1 = siyInstr->B1Value();
intptr_t b1_val = (b1 == 0) ? 0 : get_register(b1);
@ -4550,7 +4557,7 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
intptr_t addr = b1_val + d1_val;
int32_t mem_val = ReadW(addr, instr);
bool isOF = CheckOverflowForIntAdd(mem_val, i2);
bool isOF = CheckOverflowForIntAdd(mem_val, i2, int32_t);
int32_t alu_out = mem_val + i2;
SetS390ConditionCode<int32_t>(alu_out, 0);
SetS390OverflowCode(isOF);
@ -4558,7 +4565,12 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
break;
}
case AGSI: {
int8_t i2 = static_cast<int8_t>(siyInstr->I2Value());
// TODO(bcleung): Change all fooInstr->I2Value() to template functions.
// The below static cast to 8 bit and then to 32 bit is necessary
// because siyInstr->I2Value() returns a uint8_t, which a direct
// cast to int32_t could incorrectly interpret.
int8_t i2_8bit = static_cast<int8_t>(siyInstr->I2Value());
int64_t i2 = static_cast<int64_t>(i2_8bit);
int b1 = siyInstr->B1Value();
intptr_t b1_val = (b1 == 0) ? 0 : get_register(b1);
@ -4566,7 +4578,7 @@ bool Simulator::DecodeSixByteArithmetic(Instruction* instr) {
intptr_t addr = b1_val + d1_val;
int64_t mem_val = ReadDW(addr);
int isOF = CheckOverflowForIntAdd(mem_val, i2);
int isOF = CheckOverflowForIntAdd(mem_val, i2, int64_t);
int64_t alu_out = mem_val + i2;
SetS390ConditionCode<uint64_t>(alu_out, 0);
SetS390OverflowCode(isOF);

4
src/s390/simulator-s390.h
View File

@ -258,8 +258,8 @@ class Simulator {
// Helper functions to set the conditional flags in the architecture state.
bool CarryFrom(int32_t left, int32_t right, int32_t carry = 0);
bool BorrowFrom(int32_t left, int32_t right);
bool OverflowFrom(int32_t alu_out, int32_t left, int32_t right,
bool addition);
template <typename T1>
inline bool OverflowFromSigned(T1 alu_out, T1 left, T1 right, bool addition);
// Helper functions to decode common "addressing" modes
int32_t GetShiftRm(Instruction* instr, bool* carry_out);