base: Introduce versions of mul(Uns|S)igned which return two values.

This makes code which needs to call lots of different sized multiplications.

Change-Id: Id0d28be4c304214171840e7916c2e90ecfcd3840
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42360
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>

src/base/intmath.hh

@@ -44,6 +44,7 @@
 #include <cassert>
 #include <cstdint>
 #include <type_traits>
+#include <utility>
 
 #include "base/bitfield.hh"
 
@@ -223,6 +224,24 @@ mulSigned(std::make_signed_t<T> &high, std::make_signed_t<T> &low,
 #endif
 }
 
+template <typename T>
+static constexpr std::pair<std::make_unsigned_t<T>, std::make_unsigned_t<T>>
+mulUnsigned(std::make_unsigned_t<T> val_a, std::make_unsigned_t<T> val_b)
+{
+    std::make_unsigned_t<T> hi, low;
+    mulUnsigned<T>(hi, low, val_a, val_b);
+    return {hi, low};
+};
+
+template <typename T>
+static constexpr std::pair<std::make_signed_t<T>, std::make_signed_t<T>>
+mulSigned(std::make_signed_t<T> val_a, std::make_signed_t<T> val_b)
+{
+    std::make_signed_t<T> hi, low;
+    mulSigned<T>(hi, low, val_a, val_b);
+    return {hi, low};
+};
+
 /**
  * This function is used to align addresses in memory.
  *

src/base/intmath.test.cc

@@ -38,6 +38,7 @@
  */
 
 #include <gtest/gtest.h>
+#include <tuple>
 
 #include "base/intmath.hh"
 
@@ -220,6 +221,12 @@ TEST(IntmathTest, mulUnsignedWide)
     EXPECT_EQ(hi, 0x1);
     EXPECT_EQ(low, 0xfffffffffffffffe);
 
+    hi = 0;
+    low = 0;
+    std::tie(hi, low) = mulUnsigned<uint64_t>(a, b);
+    EXPECT_EQ(hi, 0x1);
+    EXPECT_EQ(low, 0xfffffffffffffffe);
+
     a = 0;
     b = 0x5555555555555555;
     mulUnsigned<uint64_t>(hi, low, a, b);
@@ -243,6 +250,12 @@ TEST(IntmathTest, mulSignedWide)
     EXPECT_EQ(hi, 0x3fffffffffffffff);
     EXPECT_EQ(low, -0x8000000000000000);
 
+    hi = 0;
+    low = 0;
+    std::tie(hi, low) = mulSigned<int64_t>(a, b);
+    EXPECT_EQ(hi, 0x3fffffffffffffff);
+    EXPECT_EQ(low, -0x8000000000000000);
+
     a = 0;
     b = -0x5555555555555555;
     mulSigned<int64_t>(hi, low, a, b);