Volume 1, Part 1: IA-32 Application Execution Model in an Intel
®
Itanium
®
System Environment
1:125
6.2.2.5.1
IA-32 Floating-point Stack
IA-32 floating-point registers are defined as follows:
• IA-32 numeric register stack is mapped to FR8 - FR15, using the Intel 8087 80-bit
IEEE floating-point format.
• For IA-32 instruction set references, floating-point registers are logically mapped
into FR8 - FR15 based on the IA-32 top-of-stack (TOS) pointer held in FCR.top. FR8
represents a physical register after the TOS adjustment and is not necessarily the
top of the logical floating-point register stack.
• For Itanium instruction set references, the floating-point register numbers are
physical and not a function of the numeric TOS pointer, e.g. references to FR8
always return the value in physical register FR8 regardless of the TOS value.
Itanium architecture-based software cannot necessarily assume that FR8 contains
the IA-32 logical register ST(0). It is highly recommended that typically IA-32
calling conventions be used which pass floating-point values through memory.
6.2.2.5.2
Special Cases
For IA-32 floating-point instructions, loading a single or double denormal results in a
normalized double-extended value placed in the target floating-point register. For
Itanium instructions, loading a single or double denormal results in an un-normalized
denormal value placed in the target floating-point register. There are two canonical
exponent values in the Itanium architecture which indicate single precision and double
precision denormals.
When transferring floating-point values from Itanium to IA-32 instructions, it is highly
recommended that typical IA-32 calling conventions be followed which pass
floating-point values through the memory stack. If software does pass floating-point
values from IA-32 to Itanium architecture-based code via the floating-point registers,
software must ensure the following:
• Single or double precision Itanium denormals must be converted into a normalized
double extended precision value expected by IA-32 instructions. Software can
convert Itanium denormals by multiplying by 1.0 in double extended precision
(
fma.sfx fr = fr, f1, f0
). If an illegal single or double precision denormal is
Table 6-6.
IA-32 Floating-point Register Mappings
Intel
®
Itanium
®
Reg
IA-32 Reg
Size (bits)
Description
FR8
ST[(TOS + N)==0]
80
IA-32 numeric register stack
Accesses to FR8 - FR15 by Intel
®
Itanium
®
instructions ignore the IA-32 TOS adjustment
IA-32 accesses use the TOS adjustment for a
given register N
FR9
ST[(TOS + N)==1]
FR10
ST[(TOS + N)==2]
FR11
ST[(TOS + N)==3]
FR12
ST[(TOS + N)==4]
FR13
ST[(TOS + N)==5]
FR14
ST[(TOS + N)==6]
FR15
ST[(TOS + N)==7]
FCR (AR21)
FCW, MXCSR
64
IA-32 numeric and SSE control register
FSR (AR28)
FSW,FTW, MXCSR
64
IA-32 numeric and SSE status and tag word
FIR (AR29)
FOP, FCS, FIP
64
IA-32 numeric instruction pointer
FDR (AR30)
FDS, FEA
48
IA-32 numeric data pointer
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...