JitArm64: Use LSL+CLS for classifying floats

This is a little trick I came up with that lets us restructure our float
classification code so we can exit earlier when the float is normal,
which is the case more often than not.

First we shift left by 1 to get rid of the sign bit, and then we count
the number of leading sign bits. If the result is less than 10 (for
doubles) or 7 (for floats), the float is normal. This is because, if the
float isn't normal, the exponent is either all zeroes or all ones.

1 files changed, 4 insertions, 0 deletions

diff --git a/Source/UnitTests/Core/PowerPC/JitArm64/FPRF.cpp b/Source/UnitTests/Core/PowerPC/JitArm64/FPRF.cpp
index 0b7e250ae6..cb19980949 100644
--- a/Source/UnitTests/Core/PowerPC/JitArm64/FPRF.cpp
+++ b/Source/UnitTests/Core/PowerPC/JitArm64/FPRF.cpp
@@ -84,6 +84,8 @@ TEST(JitArm64, FPRF)
     const u32 expected_double = RunUpdateFPRF(
         ppc_state, [&] { ppc_state.UpdateFPRFDouble(Common::BitCast<double>(double_input)); });
     const u32 actual_double = RunUpdateFPRF(ppc_state, [&] { test.fprf_double(double_input); });
+    if (expected_double != actual_double)
+      fmt::print("{:016x} -> {:08x} == {:08x}\n", double_input, actual_double, expected_double);
     EXPECT_EQ(expected_double, actual_double);
 
     const u32 single_input = ConvertToSingle(double_input);
@@ -91,6 +93,8 @@ TEST(JitArm64, FPRF)
     const u32 expected_single = RunUpdateFPRF(
         ppc_state, [&] { ppc_state.UpdateFPRFSingle(Common::BitCast<float>(single_input)); });
     const u32 actual_single = RunUpdateFPRF(ppc_state, [&] { test.fprf_single(single_input); });
+    if (expected_single != actual_single)
+      fmt::print("{:08x} -> {:08x} == {:08x}\n", single_input, actual_single, expected_single);
     EXPECT_EQ(expected_single, actual_single);
   }
 }