Sandipan Das has uploaded this change for review. (
https://gem5-review.googlesource.com/c/public/gem5/+/16623
Change subject: arch-power: Add fixed-point doubleword arithmetic divide
extended instructions
......................................................................
arch-power: Add fixed-point doubleword arithmetic divide extended
instructions
This adds the following arithmetic instructions:
* Divide Doubleword Extended (divde[o][.])
* Divide Doubleword Extended Unsigned (divdeu[o][.])
Change-Id: I535605fa6d32153054d259bcb14b952a26a1372a
Signed-off-by: Sandipan Das <[email protected]>
---
M src/arch/power/insts/integer.hh
M src/arch/power/isa/decoder.isa
2 files changed, 120 insertions(+), 0 deletions(-)
diff --git a/src/arch/power/insts/integer.hh
b/src/arch/power/insts/integer.hh
index 573f218..4ee258c 100644
--- a/src/arch/power/insts/integer.hh
+++ b/src/arch/power/insts/integer.hh
@@ -287,6 +287,100 @@
return std::make_tuple(rlo, rhi);
}
+ /**
+ * Compute overflow, 64-bit quotient and 64-bit remainder of
+ * 128-bit by 64-bit unsigned integer division based on
+ * https://codereview.stackexchange.com/a/71013
+ */
+ inline std::tuple<bool, uint64_t, uint64_t>
+ divide(uint64_t ralo, uint64_t rahi, uint64_t rb) const
+ {
+ bool ov;
+ uint64_t q, r;
+ #if defined(__SIZEOF_INT128__)
+ if (rb == 0) {
+ ov = true;
+ } else {
+ __uint128_t ra = ((__uint128_t)rahi << 64) | ralo;
+ __uint128_t res = ra / rb;
+ q = res;
+ r = ra % rb;
+ ov = res > UINT64_MAX;
+ }
+ #else
+ uint64_t c = 0;
+
+ if (rb == 0) {
+ ov = true;
+ } else if (rahi == 0) {
+ q = ralo / rb;
+ r = ralo % rb;
+ ov = false;
+ } else if (rahi >= rb) {
+ ov = true;
+ } else {
+ for (int i = 0; i < 64; ++i) {
+ c = rahi >> 63;
+ rahi = (rahi << 1) | (ralo >> 63);
+ if (c || (rahi >= rb)) {
+ rahi -= rb;
+ c = 1;
+ } else {
+ c = 0;
+ }
+ ralo = (ralo << 1) | c;
+ }
+ q = ralo;
+ r = rahi;
+ ov = false;
+ }
+ #endif
+ return std::make_tuple(ov, q, r);
+ }
+
+ /**
+ * Compute overflow, 64-bit quotient and 64-bit remainder of
+ * 128-bit by 64-bit signed integer division
+ */
+ inline std::tuple<bool, int64_t, int64_t>
+ divide(uint64_t ralo, int64_t rahi, int64_t rb) const
+ {
+ bool ov;
+ int64_t q, r;
+ #if defined(__SIZEOF_INT128__)
+ if (rb == 0) {
+ ov = true;
+ } else {
+ __int128_t ra = ((__int128_t)rahi << 64) | ralo;
+ __int128_t res = ra / rb;
+ q = res;
+ r = ra % rb;
+ ov = res != q;
+ }
+ #else
+ bool raneg = rahi < 0;
+ bool rbneg = rb < 0;
+
+ if (raneg) {
+ ralo = ~(ralo);
+ rahi = ~(rahi);
+ if (ralo == -1ULL) {
+ ralo = 0;
+ rahi++;
+ } else {
+ ralo++;
+ }
+ }
+
+ if (rbneg) rb = -rb;
+ std::tie(ov, q, r) = divide(ralo, (uint64_t)rahi, (uint64_t)rb);
+ if (raneg ^ rbneg) q = -q;
+ if (raneg) r = -r;
+ if (!ov) ov = ((q < 0) ^ (raneg ^ rbneg));
+ #endif
+ return std::make_tuple(ov, q, r);
+ }
+
std::string generateDisassembly(
Addr pc, const SymbolTable *symtab) const override;
};
diff --git a/src/arch/power/isa/decoder.isa b/src/arch/power/isa/decoder.isa
index 828d150..af92902 100644
--- a/src/arch/power/isa/decoder.isa
+++ b/src/arch/power/isa/decoder.isa
@@ -745,6 +745,32 @@
}
}},
true);
+
+ 425: divde({{
+ int64_t src1 = Ra_sd;
+ int64_t src2 = Rb_sd;
+ int64_t res;
+ std::tie(setOV, res, std::ignore) = divide(0, src1,
src2);
+ if (!setOV) {
+ Rt = res;
+ } else {
+ Rt = 0;
+ }
+ }},
+ true);
+
+ 393: divdeu({{
+ uint64_t src1 = Ra;
+ uint64_t src2 = Rb;
+ uint64_t res;
+ std::tie(setOV, res, std::ignore) = divide(0, src1,
src2);
+ if (!setOV) {
+ Rt = res;
+ } else {
+ Rt = 0;
+ }
+ }},
+ true);
}
default: decode XFX_XO {
--
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Gerrit-Project: public/gem5
Gerrit-Branch: master
Gerrit-Change-Id: I535605fa6d32153054d259bcb14b952a26a1372a
Gerrit-Change-Number: 16623
Gerrit-PatchSet: 1
Gerrit-Owner: Sandipan Das <[email protected]>
Gerrit-MessageType: newchange
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