assembler: Simplify FLIImpl table

We can just use the iterator to derive the index instead of making it a table entry (in hindsight, I don't know why I didn't do this to begin with).
lioncash · Jan 10, 2024 · 4b2dd73 · 4b2dd73
1 parent f566c33
commit 4b2dd73
Showing 1 changed file with 37 additions and 36 deletions.
diff --git a/src/assembler.cpp b/src/assembler.cpp
@@ -4,7 +4,7 @@
 #include <algorithm>
 #include <array>
 #include <cstring>
-#include <utility>
+#include <iterator>
 
 namespace biscuit {
 namespace {
@@ -1524,49 +1524,50 @@ void Assembler::FCVT_H_LU(FPR rd, GPR rs1, RMode rmode) noexcept {
 
 static void FLIImpl(CodeBuffer& buffer, uint32_t funct7, FPR rd, double value) noexcept {
     static constexpr std::array fli_table{
-        std::pair{0xBFF0000000000000ULL, 0U},   // -1.0
-        std::pair{0x0010000000000000ULL, 1U},   // Minimum positive normal
-        std::pair{0x3EF0000000000000ULL, 2U},   // 1.0 * 2^-16
-        std::pair{0x3F00000000000000ULL, 3U},   // 1.0 * 2^-15
-        std::pair{0x3F70000000000000ULL, 4U},   // 1.0 * 2^-8
-        std::pair{0x3F80000000000000ULL, 5U},   // 1.0 * 2^-7
-        std::pair{0x3FB0000000000000ULL, 6U},   // 1.0 * 2^-4
-        std::pair{0x3FC0000000000000ULL, 7U},   // 1.0 * 2^-3
-        std::pair{0x3FD0000000000000ULL, 8U},   // 0.25
-        std::pair{0x3FD4000000000000ULL, 9U},   // 0.3125
-        std::pair{0x3FD8000000000000ULL, 10U},  // 0.375
-        std::pair{0x3FDC000000000000ULL, 11U},  // 0.4375
-        std::pair{0x3FE0000000000000ULL, 12U},  // 0.5
-        std::pair{0x3FE4000000000000ULL, 13U},  // 0.625
-        std::pair{0x3FE8000000000000ULL, 14U},  // 0.75
-        std::pair{0x3FEC000000000000ULL, 15U},  // 0.875
-        std::pair{0x3FF0000000000000ULL, 16U},  // 1.0
-        std::pair{0x3FF4000000000000ULL, 17U},  // 1.25
-        std::pair{0x3FF8000000000000ULL, 18U},  // 1.5
-        std::pair{0x3FFC000000000000ULL, 19U},  // 1.75
-        std::pair{0x4000000000000000ULL, 20U},  // 2.0
-        std::pair{0x4004000000000000ULL, 21U},  // 2.5
-        std::pair{0x4008000000000000ULL, 22U},  // 3
-        std::pair{0x4010000000000000ULL, 23U},  // 4
-        std::pair{0x4020000000000000ULL, 24U},  // 8
-        std::pair{0x4030000000000000ULL, 25U},  // 16
-        std::pair{0x4060000000000000ULL, 26U},  // 2^7
-        std::pair{0x4070000000000000ULL, 27U},  // 2^8
-        std::pair{0x40E0000000000000ULL, 28U},  // 2^15
-        std::pair{0x40F0000000000000ULL, 29U},  // 2^16
-        std::pair{0x7FF0000000000000ULL, 30U},  // +inf
-        std::pair{0x7FF8000000000000ULL, 31U},  // Canonical NaN
+        0xBFF0000000000000ULL,   // -1.0
+        0x0010000000000000ULL,   // Minimum positive normal
+        0x3EF0000000000000ULL,   // 1.0 * 2^-16
+        0x3F00000000000000ULL,   // 1.0 * 2^-15
+        0x3F70000000000000ULL,   // 1.0 * 2^-8
+        0x3F80000000000000ULL,   // 1.0 * 2^-7
+        0x3FB0000000000000ULL,   // 1.0 * 2^-4
+        0x3FC0000000000000ULL,   // 1.0 * 2^-3
+        0x3FD0000000000000ULL,   // 0.25
+        0x3FD4000000000000ULL,   // 0.3125
+        0x3FD8000000000000ULL,  // 0.375
+        0x3FDC000000000000ULL,  // 0.4375
+        0x3FE0000000000000ULL,  // 0.5
+        0x3FE4000000000000ULL,  // 0.625
+        0x3FE8000000000000ULL,  // 0.75
+        0x3FEC000000000000ULL,  // 0.875
+        0x3FF0000000000000ULL,  // 1.0
+        0x3FF4000000000000ULL,  // 1.25
+        0x3FF8000000000000ULL,  // 1.5
+        0x3FFC000000000000ULL,  // 1.75
+        0x4000000000000000ULL,  // 2.0
+        0x4004000000000000ULL,  // 2.5
+        0x4008000000000000ULL,  // 3
+        0x4010000000000000ULL,  // 4
+        0x4020000000000000ULL,  // 8
+        0x4030000000000000ULL,  // 16
+        0x4060000000000000ULL,  // 2^7
+        0x4070000000000000ULL,  // 2^8
+        0x40E0000000000000ULL,  // 2^15
+        0x40F0000000000000ULL,  // 2^16
+        0x7FF0000000000000ULL,  // +inf
+        0x7FF8000000000000ULL,  // Canonical NaN
     };
 
     uint64_t ivalue{};
     std::memcpy(&ivalue, &value, sizeof(uint64_t));
 
-    const auto iter = std::find_if(fli_table.cbegin(), fli_table.cend(), [ivalue](const auto& entry) {
-        return entry.first == ivalue;
+    const auto iter = std::find_if(fli_table.cbegin(), fli_table.cend(), [ivalue](uint64_t entry) {
+        return entry == ivalue;
     });
     BISCUIT_ASSERT(iter != fli_table.cend());
 
-    EmitRType(buffer, funct7, f1, GPR{iter->second}, 0b000, rd, 0b1010011);
+    const auto index = static_cast<uint32_t>(std::distance(fli_table.cbegin(), iter));
+    EmitRType(buffer, funct7, f1, GPR{index}, 0b000, rd, 0b1010011);
 }
 
 void Assembler::FLI_D(FPR rd, double value) noexcept {