arch-riscv: Fix floating-point conversion bugs
Using the fetestexcept function to check for specific types of floating
point exceptions is unreliable for some kinds of
floating-point-to-integer conversion operations. RISC-V code used to
make use of them to check for some exceptional cases like overflow and
underflow, which caused incorrect output when compiler optimization is
turned on. This patch changes the use of fetestexcept to explicit checks
for those exceptional cases.
Change-Id: Id983906ea0664dc246e115a9e470d9ab7733bde1
Reviewed-on: https://gem5-review.googlesource.com/6402
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Alec Roelke <ar4jc@virginia.edu>
diff --git a/src/arch/riscv/isa/decoder.isa b/src/arch/riscv/isa/decoder.isa
index 435266c..baae581 100644
--- a/src/arch/riscv/isa/decoder.isa
+++ b/src/arch/riscv/isa/decoder.isa
@@ -1338,31 +1338,31 @@
if (std::isnan(fs1)) {
Rd_sd = numeric_limits<int32_t>::max();
FFLAGS |= FloatInvalid;
+ } else if (fs1 >= numeric_limits<int32_t>::max()) {
+ Rd_sd = numeric_limits<int32_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (fs1 <= numeric_limits<int32_t>::min()) {
+ Rd_sd = numeric_limits<int32_t>::min();
+ FFLAGS |= FloatInvalid;
} else {
Rd_sd = (int32_t)fs1;
- if (fetestexcept(FE_INVALID)) {
- if (signbit(fs1)) {
- Rd_sd = numeric_limits<int32_t>::min();
- } else {
- Rd_sd = numeric_limits<int32_t>::max();
- }
- feclearexcept(FE_INEXACT);
- }
}
}}, FloatCvtOp);
0x1: fcvt_wu_s({{
uint32_t temp;
float fs1 = reinterpret_cast<float&>(temp = Fs1_bits);
- if (fs1 < 0.0) {
+ if (std::isnan(fs1)) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (fs1 < 0.0) {
Rd = 0;
FFLAGS |= FloatInvalid;
+ } else if (fs1 > numeric_limits<uint32_t>::max()) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
} else {
Rd = (uint32_t)fs1;
- if (fetestexcept(FE_INVALID)) {
- Rd = numeric_limits<uint64_t>::max();
- feclearexcept(FE_INEXACT);
- }
}
}}, FloatCvtOp);
0x2: fcvt_l_s({{
@@ -1372,79 +1372,89 @@
if (std::isnan(fs1)) {
Rd_sd = numeric_limits<int64_t>::max();
FFLAGS |= FloatInvalid;
+ } else if (fs1 > numeric_limits<int64_t>::max()) {
+ Rd_sd = numeric_limits<int64_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (fs1 < numeric_limits<int64_t>::min()) {
+ Rd_sd = numeric_limits<int64_t>::min();
+ FFLAGS |= FloatInvalid;
} else {
Rd_sd = (int64_t)fs1;
- if (fetestexcept(FE_INVALID)) {
- if (signbit(fs1)) {
- Rd_sd = numeric_limits<int64_t>::min();
- } else {
- Rd_sd = numeric_limits<int64_t>::max();
- }
- feclearexcept(FE_INEXACT);
- }
}
}}, FloatCvtOp);
0x3: fcvt_lu_s({{
uint32_t temp;
float fs1 = reinterpret_cast<float&>(temp = Fs1_bits);
- if (fs1 < 0.0) {
+ if (std::isnan(fs1)) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (fs1 < 0.0) {
Rd = 0;
FFLAGS |= FloatInvalid;
+ } else if (fs1 > numeric_limits<uint64_t>::max()) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
} else {
Rd = (uint64_t)fs1;
- if (fetestexcept(FE_INVALID)) {
- Rd = numeric_limits<uint64_t>::max();
- feclearexcept(FE_INEXACT);
- }
}
}}, FloatCvtOp);
}
0x61: decode CONV_SGN {
0x0: fcvt_w_d({{
- Rd_sd = (int32_t)Fs1;
- if (fetestexcept(FE_INVALID)) {
- if (Fs1 < 0.0) {
- Rd_sd = numeric_limits<int32_t>::min();
- } else {
- Rd_sd = numeric_limits<int32_t>::max();
- }
- feclearexcept(FE_INEXACT);
+ if (std::isnan(Fs1)) {
+ Rd_sd = numeric_limits<int32_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (Fs1 > numeric_limits<int32_t>::max()) {
+ Rd_sd = numeric_limits<int32_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (Fs1 < numeric_limits<int32_t>::min()) {
+ Rd_sd = numeric_limits<int32_t>::min();
+ FFLAGS |= FloatInvalid;
+ } else {
+ Rd_sd = (int32_t)Fs1;
}
}}, FloatCvtOp);
0x1: fcvt_wu_d({{
- if (Fs1 < 0.0) {
+ if (std::isnan(Fs1)) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (Fs1 < 0) {
Rd = 0;
FFLAGS |= FloatInvalid;
+ } else if (Fs1 > numeric_limits<uint32_t>::max()) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
} else {
Rd = (uint32_t)Fs1;
- if (fetestexcept(FE_INVALID)) {
- Rd = numeric_limits<uint64_t>::max();
- feclearexcept(FE_INEXACT);
- }
}
}}, FloatCvtOp);
0x2: fcvt_l_d({{
- Rd_sd = Fs1;
- if (fetestexcept(FE_INVALID)) {
- if (Fs1 < 0.0) {
- Rd_sd = numeric_limits<int64_t>::min();
- } else {
- Rd_sd = numeric_limits<int64_t>::max();
- }
- feclearexcept(FE_INEXACT);
+ if (std::isnan(Fs1)) {
+ Rd_sd = numeric_limits<int64_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (Fs1 > numeric_limits<int64_t>::max()) {
+ Rd_sd = numeric_limits<int64_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (Fs1 < numeric_limits<int64_t>::min()) {
+ Rd_sd = numeric_limits<int64_t>::min();
+ FFLAGS |= FloatInvalid;
+ } else {
+ Rd_sd = Fs1;
}
}}, FloatCvtOp);
0x3: fcvt_lu_d({{
- if (Fs1 < 0.0) {
+ if (std::isnan(Fs1)) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
+ } else if (Fs1 < 0) {
Rd = 0;
FFLAGS |= FloatInvalid;
+ } else if (Fs1 > numeric_limits<uint64_t>::max()) {
+ Rd = numeric_limits<uint64_t>::max();
+ FFLAGS |= FloatInvalid;
} else {
- Rd = (uint64_t)Fs1;
- if (fetestexcept(FE_INVALID)) {
- Rd = numeric_limits<uint64_t>::max();
- feclearexcept(FE_INEXACT);
- }
+ Rd = Fs1;
}
}}, FloatCvtOp);
}
