Initialize float constants using bit_cast

This is a compile fix: the constants were defined
as uint32_t/uint64_t while being declared as float/double.

Changed type in the definition to match declaration and
used bit_cast to make sure the bit pattern is as expected.

Bug: chromium:1151843
Change-Id: I129af71cd9a3dc97f01d2b58f14953345be84382
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2551111Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71496}

src/codegen/arm64/instructions-arm64-constants.cc

@@ -3,52 +3,79 @@
 // found in the LICENSE file.
 
 #include <cstdint>
+
 #include "include/v8config.h"
 #include "src/base/macros.h"
+#include "src/codegen/arm64/constants-arm64.h"
 
 namespace v8 {
 namespace internal {
 
 // ISA constants. --------------------------------------------------------------
 
-// The following code initializes float/double variables with bit patterns
-// without using static initializers (which is surprisingly difficult in
-// C++).  These variables are used by client code as extern float16,
-// extern float and extern double types, which works because (I think) the
-// linker ignores the types.  This is kept in a separate source file to
-// avoid breaking jumbo builds.
+// The following code initializes float/double variables with bit patterns.
 //
 // TODO(mostynb): replace these with std::numeric_limits constexpr's where
 // possible, and figure out how to replace *DefaultNaN with something clean,
 // then move this code back into instructions-arm64.cc with the same types
 // that client code uses.
 
-#if defined(V8_OS_WIN)
-extern "C" {
-#endif
-
-extern const uint16_t kFP16PositiveInfinity = 0x7C00;
-extern const uint16_t kFP16NegativeInfinity = 0xFC00;
-V8_EXPORT_PRIVATE extern const uint32_t kFP32PositiveInfinity = 0x7F800000;
-V8_EXPORT_PRIVATE extern const uint32_t kFP32NegativeInfinity = 0xFF800000;
-V8_EXPORT_PRIVATE extern const uint64_t kFP64PositiveInfinity =
-    0x7FF0000000000000UL;
-V8_EXPORT_PRIVATE extern const uint64_t kFP64NegativeInfinity =
-    0xFFF0000000000000UL;
+namespace integer_constants {
+constexpr uint16_t kFP16PositiveInfinity = 0x7C00;
+constexpr uint16_t kFP16NegativeInfinity = 0xFC00;
+constexpr uint32_t kFP32PositiveInfinity = 0x7F800000;
+constexpr uint32_t kFP32NegativeInfinity = 0xFF800000;
+constexpr uint64_t kFP64PositiveInfinity = 0x7FF0000000000000UL;
+constexpr uint64_t kFP64NegativeInfinity = 0xFFF0000000000000UL;
 
 // This value is a signalling NaN as both a double and as a float (taking the
 // least-significant word).
-V8_EXPORT_PRIVATE extern const uint64_t kFP64SignallingNaN = 0x7FF000007F800001;
-V8_EXPORT_PRIVATE extern const uint32_t kFP32SignallingNaN = 0x7F800001;
+constexpr uint64_t kFP64SignallingNaN = 0x7FF000007F800001;
+constexpr uint32_t kFP32SignallingNaN = 0x7F800001;
 
 // A similar value, but as a quiet NaN.
-V8_EXPORT_PRIVATE extern const uint64_t kFP64QuietNaN = 0x7FF800007FC00001;
-V8_EXPORT_PRIVATE extern const uint32_t kFP32QuietNaN = 0x7FC00001;
+constexpr uint64_t kFP64QuietNaN = 0x7FF800007FC00001;
+constexpr uint32_t kFP32QuietNaN = 0x7FC00001;
 
 // The default NaN values (for FPCR.DN=1).
-V8_EXPORT_PRIVATE extern const uint64_t kFP64DefaultNaN = 0x7FF8000000000000UL;
-V8_EXPORT_PRIVATE extern const uint32_t kFP32DefaultNaN = 0x7FC00000;
+constexpr uint64_t kFP64DefaultNaN = 0x7FF8000000000000UL;
+constexpr uint32_t kFP32DefaultNaN = 0x7FC00000;
 extern const uint16_t kFP16DefaultNaN = 0x7E00;
+}  // namespace integer_constants
+
+#if defined(V8_OS_WIN)
+extern "C" {
+#endif
+
+extern const float16 kFP16PositiveInfinity =
+    bit_cast<float16>(integer_constants::kFP16PositiveInfinity);
+extern const float16 kFP16NegativeInfinity =
+    bit_cast<float16>(integer_constants::kFP16NegativeInfinity);
+V8_EXPORT_PRIVATE extern const float kFP32PositiveInfinity =
+    bit_cast<float>(integer_constants::kFP32PositiveInfinity);
+V8_EXPORT_PRIVATE extern const float kFP32NegativeInfinity =
+    bit_cast<float>(integer_constants::kFP32NegativeInfinity);
+V8_EXPORT_PRIVATE extern const double kFP64PositiveInfinity =
+    bit_cast<double>(integer_constants::kFP64PositiveInfinity);
+V8_EXPORT_PRIVATE extern const double kFP64NegativeInfinity =
+    bit_cast<double>(integer_constants::kFP64NegativeInfinity);
+
+V8_EXPORT_PRIVATE extern const double kFP64SignallingNaN =
+    bit_cast<double>(integer_constants::kFP64SignallingNaN);
+V8_EXPORT_PRIVATE extern const float kFP32SignallingNaN =
+    bit_cast<float>(integer_constants::kFP32SignallingNaN);
+
+V8_EXPORT_PRIVATE extern const double kFP64QuietNaN =
+    bit_cast<double>(integer_constants::kFP64QuietNaN);
+V8_EXPORT_PRIVATE extern const float kFP32QuietNaN =
+    bit_cast<float>(integer_constants::kFP32QuietNaN);
+
+V8_EXPORT_PRIVATE extern const double kFP64DefaultNaN =
+    bit_cast<double>(integer_constants::kFP64DefaultNaN);
+V8_EXPORT_PRIVATE extern const float kFP32DefaultNaN =
+    bit_cast<float>(integer_constants::kFP32DefaultNaN);
+extern const float16 kFP16DefaultNaN =
+    bit_cast<float16>(integer_constants::kFP16DefaultNaN);
 
 #if defined(V8_OS_WIN)
 }  // end of extern "C"