[compiler-rt] [compiler-rt] Implement __extendxftf2 and __trunctfxf2 for x86_64 (PR #66918)

[Eli Friedman via llvm-commits]

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@@ -58,26 +80,70 @@ static const int srcSigBits = 10;
 typedef float dst_t;
 typedef uint32_t dst_rep_t;
 #define DST_REP_C UINT32_C
-static const int dstSigBits = 23;
+static const int dstBits = sizeof(dst_t) * CHAR_BIT;
+static const int dstSigFracBits = 23;
+// -1 accounts for the sign bit.
+static const int dstExpBits = dstBits - dstSigFracBits - 1;
 
 #elif defined DST_DOUBLE
 typedef double dst_t;
 typedef uint64_t dst_rep_t;
 #define DST_REP_C UINT64_C
-static const int dstSigBits = 52;
+static const int dstBits = sizeof(dst_t) * CHAR_BIT;
+static const int dstSigFracBits = 52;
+// -1 accounts for the sign bit.
+static const int dstExpBits = dstBits - dstSigFracBits - 1;
 
 #elif defined DST_QUAD
+// TODO: use fp_lib.h once QUAD_PRECISION is available on x86_64.
+#if __LDBL_MANT_DIG__ == 113
 typedef long double dst_t;
+#elif defined(__x86_64__) &&                                                   \
+    (defined(__FLOAT128__) || defined(__SIZEOF_FLOAT128__))
+typedef __float128 dst_t;
+#endif
 typedef __uint128_t dst_rep_t;
 #define DST_REP_C (__uint128_t)
-static const int dstSigBits = 112;
+static const int dstBits = sizeof(dst_t) * CHAR_BIT;
+static const int dstSigFracBits = 112;
+// -1 accounts for the sign bit.
+static const int dstExpBits = dstBits - dstSigFracBits - 1;
 
 #else
 #error Destination should be single, double, or quad precision!
 #endif // end destination precision
 
-// End of specialization parameters.  Two helper routines for conversion to and
-// from the representation of floating-point data as integer values follow.
+// End of specialization parameters.
+
+static __inline src_rep_t extract_sign_from_src(src_rep_t x) {
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efriedma-quic wrote:

We're already using the usual "inline" keyword in other places, so it should be fine to use here.  (I assume the use of __inline is an artifact from when compiler-rt was built in "c89" mode.)

https://github.com/llvm/llvm-project/pull/66918