Figure 21.7 shows the set of registers available to application programs.That is, theseregisters are visible to applications and may be read and, in most cases, written.Theregister sets include:• General registers: 128 general-purpose 64-bit registers.Associated with eachregister is a NaT bit used to track deferred speculative exceptions, as explainedin Section 21.3. Registers r0 through r31 are referred to as static; aprogram reference to any of these references is literally interpreted. Registersr32 through r127 can be used as rotating registers for software pipelining(discussed in Section 21.3) and for register stack implementation (discussedsubsequently in this section).References to these registers are virtual, and thehardware my perform register renaming dynamically.• Floating-point registers: 128 82-bit registers for floating-point numbers. Thissize is sufficient to hold IEEE 754 double extended format numbers (seeTable 9.3). Registers fr0 through fr31 are static, and registers fr32 throughfr127 can be used as rotating registers for software pipelining.
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