[libc-commits] [libc] [libc][math][c23] Fix X86_80 Special Case (PR #86924)

[Shourya Goel via libc-commits]

https://github.com/Sh0g0-1758 created https://github.com/llvm/llvm-project/pull/86924

Updates the special case of pseudo infinty as pointed in #85940

>From 3ba418899bacffc8076befad68140f272a4ff5c4 Mon Sep 17 00:00:00 2001
From: Sh0g0-1758 <shouryagoel10000 at gmail.com>
Date: Thu, 28 Mar 2024 14:48:06 +0530
Subject: [PATCH] fix infinity

---
 libc/src/__support/FPUtil/BasicOperations.h | 10 ++++++----
 libc/test/src/math/smoke/CanonicalizeTest.h |  6 +++---
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/libc/src/__support/FPUtil/BasicOperations.h b/libc/src/__support/FPUtil/BasicOperations.h
index a47931bb33900a..bdb91a98a0d357 100644
--- a/libc/src/__support/FPUtil/BasicOperations.h
+++ b/libc/src/__support/FPUtil/BasicOperations.h
@@ -185,7 +185,7 @@ LIBC_INLINE int canonicalize(T &cx, const T &x) {
     // More precisely :
     // Exponent   |       Significand      | Meaning
     //            | Bits 63-62 | Bits 61-0 |
-    // All Ones   |     00     |    Zero   | Pseudo Infinity, Value = Infinty
+    // All Ones   |     00     |    Zero   | Pseudo Infinity, Value = SNaN
     // All Ones   |     00     |  Non-Zero | Pseudo NaN, Value = SNaN
     // All Ones   |     01     | Anything  | Pseudo NaN, Value = SNaN
     //            |   Bit 63   | Bits 62-0 |
@@ -199,9 +199,11 @@ LIBC_INLINE int canonicalize(T &cx, const T &x) {
     int exponent = sx.get_biased_exponent();
     if (exponent == 0x7FFF) {
       if (!bit63 && !bit62) {
-        if (mantissa == 0)
-          cx = FPBits<T>::inf(sx.sign()).get_val();
-        else {
+        if (mantissa == 0) {
+          cx = FPBits<T>::quiet_nan(sx.sign(), mantissa).get_val();
+          raise_except_if_required(FE_INVALID);
+          return 1;
+        } else {
           cx = FPBits<T>::quiet_nan(sx.sign(), mantissa).get_val();
           raise_except_if_required(FE_INVALID);
           return 1;
diff --git a/libc/test/src/math/smoke/CanonicalizeTest.h b/libc/test/src/math/smoke/CanonicalizeTest.h
index c8af83f1983881..1891d47922cf88 100644
--- a/libc/test/src/math/smoke/CanonicalizeTest.h
+++ b/libc/test/src/math/smoke/CanonicalizeTest.h
@@ -55,12 +55,12 @@ class CanonicalizeTest : public LIBC_NAMESPACE::testing::Test {
       T cx;
       // Exponent   |       Significand      | Meaning
       //            | Bits 63-62 | Bits 61-0 |
-      // All Ones   |     00     |    Zero   | Pseudo Infinity, Value = Infinty
+      // All Ones   |     00     |    Zero   | Pseudo Infinity, Value = SNaN
 
       FPBits test1((UInt128(0x7FFF) << 64) + UInt128(0x0000000000000000));
       const T test1_val = test1.get_val();
-      TEST_SPECIAL(cx, test1_val, 0, 0);
-      EXPECT_FP_EQ(cx, inf);
+      TEST_SPECIAL(cx, test1_val, 1, FE_INVALID);
+      EXPECT_FP_EQ(cx, aNaN);
 
       // Exponent   |       Significand      | Meaning
       //            | Bits 63-62 | Bits 61-0 |