[unsigned] int -> float soft-float conversions for single- and double-precision

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@107535 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/floatsidf.c b/lib/floatsidf.c
new file mode 100644
index 000000000..ebd1a6b60
--- /dev/null
+++ b/lib/floatsidf.c
@@ -0,0 +1,54 @@
+//===-- lib/floatsidf.c - integer -> double-precision conversion --*- C -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements integer to double-precision conversion for the
+// compiler-rt library in the IEEE-754 default round-to-nearest, ties-to-even
+// mode.
+//
+//===----------------------------------------------------------------------===//
+
+#define DOUBLE_PRECISION
+#include "fp_lib.h"
+
+fp_t __floatsidf(int a) {
+    
+    const int aWidth = sizeof a * CHAR_BIT;
+    
+    // Handle zero as a special case to protect clz
+    if (a == 0)
+        return fromRep(0);
+    
+    // All other cases begin by extracting the sign and absolute value of a
+    rep_t sign = 0;
+    if (a < 0) {
+        sign = signBit;
+        a = -a;
+    }
+    
+    // Exponent of (fp_t)a is the width of abs(a).
+    const int exponent = (aWidth - 1) - __builtin_clz(a);
+    rep_t result;
+    
+    // Shift a into the significand field, rounding if it is a right-shift
+    if (exponent <= significandBits) {
+        const int shift = significandBits - exponent;
+        result = (rep_t)a << shift ^ implicitBit;
+    } else {
+        const int shift = exponent - significandBits;
+        result = (rep_t)a >> shift ^ implicitBit;
+        rep_t round = (rep_t)a << (typeWidth - shift);
+        if (round > signBit) result++;
+        if (round == signBit) result += result & 1;
+    }
+    
+    // Insert the exponent
+    result += (rep_t)(exponent + exponentBias) << significandBits;
+    // Insert the sign bit and return
+    return fromRep(result | sign);
+}