ARM64: Fix and improve MacroAssembler::Printf.

src/arm64/instructions-arm64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ARM64_INSTRUCTIONS_ARM64_H_
 #define V8_ARM64_INSTRUCTIONS_ARM64_H_
 
 #include "globals.h"
 #include "utils.h"
 #include "arm64/constants-arm64.h"
@@ skipping 398 matching lines @@
 // Indicate to the Debugger that the instruction is a redirected call.
 const Instr kImmExceptionIsRedirectedCall = 0xca11;
 
 // Represent unreachable code. This is used as a guard in parts of the code that
 // should not be reachable, such as in data encoded inline in the instructions.
 const Instr kImmExceptionIsUnreachable = 0xdebf;
 
 // A pseudo 'printf' instruction. The arguments will be passed to the platform
 // printf method.
 const Instr kImmExceptionIsPrintf = 0xdeb1;
-// Parameters are stored in ARM64 registers as if the printf pseudo-instruction
-// was a call to the real printf method:
-//
-// x0: The format string, then either of:
+// Most parameters are stored in ARM64 registers as if the printf
+// pseudo-instruction was a call to the real printf method:
+//      x0: The format string.
 //   x1-x7: Optional arguments.
 //   d0-d7: Optional arguments.
 //
-// Floating-point and integer arguments are passed in separate sets of
-// registers in AAPCS64 (even for varargs functions), so it is not possible to
-// determine the type of location of each arguments without some information
-// about the values that were passed in. This information could be retrieved
-// from the printf format string, but the format string is not trivial to
-// parse so we encode the relevant information with the HLT instruction.
-// - Type
-//    Either kRegister or kFPRegister, but stored as a uint32_t because there's
-//    no way to guarantee the size of the CPURegister::RegisterType enum.
-const unsigned kPrintfTypeOffset = 1 * kInstructionSize;
-const unsigned kPrintfLength = 2 * kInstructionSize;
+// Also, the argument layout is described inline in the instructions:
+//  - arg_count: The number of arguments.
+//  - arg_pattern: A set of PrintfArgPattern values, packed into two-bit fields.
+//
+// Floating-point and integer arguments are passed in separate sets of registers
+// in AAPCS64 (even for varargs functions), so it is not possible to determine
+// the type of each argument without some information about the values that were
+// passed in. This information could be retrieved from the printf format string,
+// but the format string is not trivial to parse so we encode the relevant
+// information with the HLT instruction.
+const unsigned kPrintfArgCountOffset = 1 * kInstructionSize;
+const unsigned kPrintfArgPatternListOffset = 2 * kInstructionSize;
+const unsigned kPrintfLength = 3 * kInstructionSize;
+
+const unsigned kPrintfMaxArgCount = 4;
+
+// The argument pattern is a set of two-bit-fields, each with one of the
+// following values:
+enum PrintfArgPattern {
+  kPrintfArgW = 1,
+  kPrintfArgX = 2,
+  // There is no kPrintfArgS because floats are always converted to doubles in C
+  // varargs calls.
+  kPrintfArgD = 3
+};
+static const unsigned kPrintfArgPatternBits = 2;
 
 // A pseudo 'debug' instruction.
 const Instr kImmExceptionIsDebug = 0xdeb0;
 // Parameters are inlined in the code after a debug pseudo-instruction:
 // - Debug code.
 // - Debug parameters.
 // - Debug message string. This is a NULL-terminated ASCII string, padded to
 //   kInstructionSize so that subsequent instructions are correctly aligned.
 // - A kImmExceptionIsUnreachable marker, to catch accidental execution of the
 //   string data.
@@ skipping 39 matching lines @@
   TRACE_ENABLE   = 1 << 6,
   TRACE_DISABLE  = 2 << 6,
   TRACE_OVERRIDE = 3 << 6
 };
 
 
 } }  // namespace v8::internal
 
 
 #endif  // V8_ARM64_INSTRUCTIONS_ARM64_H_