Revert "ADT: add <bit> header, implement C++20 bit_cast, use"

Bots sad. Looks like missing std::is_trivially_copyable.

llvm-svn: 341730

1 files changed, 14 insertions, 7 deletions

diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index f2f5cca946f..f3c2ca5dab9 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -19,7 +19,6 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
-#include "llvm/ADT/bit.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -713,20 +712,24 @@ APInt llvm::APIntOps::GreatestCommonDivisor(APInt A, APInt B) {
 }
 
 APInt llvm::APIntOps::RoundDoubleToAPInt(double Double, unsigned width) {
-  uint64_t I = bit_cast<uint64_t>(Double);
+  union {
+    double D;
+    uint64_t I;
+  } T;
+  T.D = Double;
 
   // Get the sign bit from the highest order bit
-  bool isNeg = I >> 63;
+  bool isNeg = T.I >> 63;
 
   // Get the 11-bit exponent and adjust for the 1023 bit bias
-  int64_t exp = ((I >> 52) & 0x7ff) - 1023;
+  int64_t exp = ((T.I >> 52) & 0x7ff) - 1023;
 
   // If the exponent is negative, the value is < 0 so just return 0.
   if (exp < 0)
     return APInt(width, 0u);
 
   // Extract the mantissa by clearing the top 12 bits (sign + exponent).
-  uint64_t mantissa = (I & (~0ULL >> 12)) | 1ULL << 52;
+  uint64_t mantissa = (T.I & (~0ULL >> 12)) | 1ULL << 52;
 
   // If the exponent doesn't shift all bits out of the mantissa
   if (exp < 52)
@@ -803,8 +806,12 @@ double APInt::roundToDouble(bool isSigned) const {
 
   // The leading bit of mantissa is implicit, so get rid of it.
   uint64_t sign = isNeg ? (1ULL << (APINT_BITS_PER_WORD - 1)) : 0;
-  uint64_t I = sign | (exp << 52) | mantissa;
-  return bit_cast<double>(I);
+  union {
+    double D;
+    uint64_t I;
+  } T;
+  T.I = sign | (exp << 52) | mantissa;
+  return T.D;
 }
 
 // Truncate to new width.