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20e2d517e2
Estimated hours taken: 0.5 by me (+ unknown by Sergey Khorev) Branches: main, release Commit Sergey Khorev's patch to port Mercury to the ARM architecture. configure.in: runtime/mercury_regs.h: runtime/machdeps/arm_regs.h: Global registers for ARM. runtime/Mmakefile: Add arm_regs.h to the list of machine dependent headers. runtime/machdeps/ARM_REGS: Add documentation from the gcc source code on what registers can be used. runtime/machdeps/arm_regtest: Test what registers we can use on ARM.
118 lines
4.3 KiB
Plaintext
118 lines
4.3 KiB
Plaintext
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This file contains the relevant part of config/arm/arm.h from the
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GNU C source code which describes how each register is used.
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/* Register allocation in ARM Procedure Call Standard (as used on RISCiX):
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(S - saved over call).
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r0 * argument word/integer result
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r1-r3 argument word
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r4-r8 S register variable
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r9 S (rfp) register variable (real frame pointer)
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r10 F S (sl) stack limit (used by -mapcs-stack-check)
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r11 F S (fp) argument pointer
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r12 (ip) temp workspace
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r13 F S (sp) lower end of current stack frame
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r14 (lr) link address/workspace
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r15 F (pc) program counter
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f0 floating point result
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f1-f3 floating point scratch
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f4-f7 S floating point variable
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cc This is NOT a real register, but is used internally
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to represent things that use or set the condition
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codes.
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sfp This isn't either. It is used during rtl generation
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since the offset between the frame pointer and the
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auto's isn't known until after register allocation.
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afp Nor this, we only need this because of non-local
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goto. Without it fp appears to be used and the
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elimination code won't get rid of sfp. It tracks
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fp exactly at all times.
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*: See CONDITIONAL_REGISTER_USAGE */
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/* The stack backtrace structure is as follows:
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fp points to here: | save code pointer | [fp]
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| return link value | [fp, #-4]
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| return sp value | [fp, #-8]
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| return fp value | [fp, #-12]
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[| saved r10 value |]
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[| saved r9 value |]
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[| saved r8 value |]
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[| saved r7 value |]
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[| saved r6 value |]
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[| saved r5 value |]
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[| saved r4 value |]
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[| saved r3 value |]
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[| saved r2 value |]
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[| saved r1 value |]
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[| saved r0 value |]
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[| saved f7 value |] three words
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[| saved f6 value |] three words
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[| saved f5 value |] three words
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[| saved f4 value |] three words
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r0-r3 are not normally saved in a C function. */
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/* 1 for registers that have pervasive standard uses
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and are not available for the register allocator. */
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#define FIXED_REGISTERS \
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{ \
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0,0,0,0,0,0,0,0, \
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0,0,0,0,0,1,0,1, \
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0,0,0,0,0,0,0,0, \
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1,1,1 \
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}
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/* 1 for registers not available across function calls.
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These must include the FIXED_REGISTERS and also any
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registers that can be used without being saved.
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The latter must include the registers where values are returned
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and the register where structure-value addresses are passed.
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Aside from that, you can include as many other registers as you like.
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The CC is not preserved over function calls on the ARM 6, so it is
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easier to assume this for all. SFP is preserved, since FP is. */
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#define CALL_USED_REGISTERS \
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{ \
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1,1,1,1,0,0,0,0, \
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0,0,0,0,1,1,1,1, \
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1,1,1,1,0,0,0,0, \
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1,1,1 \
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}
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#ifndef SUBTARGET_CONDITIONAL_REGISTER_USAGE
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#define SUBTARGET_CONDITIONAL_REGISTER_USAGE
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#endif
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#define CONDITIONAL_REGISTER_USAGE \
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{ \
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int regno; \
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\
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if (TARGET_SOFT_FLOAT || TARGET_THUMB) \
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{ \
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for (regno = FIRST_ARM_FP_REGNUM; \
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regno <= LAST_ARM_FP_REGNUM; ++regno) \
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fixed_regs[regno] = call_used_regs[regno] = 1; \
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} \
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if (PIC_OFFSET_TABLE_REGNUM != INVALID_REGNUM) \
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{ \
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fixed_regs[PIC_OFFSET_TABLE_REGNUM] = 1; \
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call_used_regs[PIC_OFFSET_TABLE_REGNUM] = 1; \
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} \
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else if (TARGET_APCS_STACK) \
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{ \
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fixed_regs[10] = 1; \
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call_used_regs[10] = 1; \
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} \
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if (TARGET_APCS_FRAME) \
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{ \
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fixed_regs[ARM_HARD_FRAME_POINTER_REGNUM] = 1; \
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call_used_regs[ARM_HARD_FRAME_POINTER_REGNUM] = 1; \
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} \
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SUBTARGET_CONDITIONAL_REGISTER_USAGE \
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}
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