This file records register use conventions and info for the 4 supported platforms (since it is ABI dependent). This is so as to avoid having to endlessly re-look up this info in ABI documents. ----------------------- x86-linux ~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? -------------------------------------------------------------- eax n n int[31:0] retreg y ebx y n y ecx n n y edx n n int[63:32] retreg y esi y n y edi y n y ebp y n & guest state esp reserved n/a n/a eflags n n/a y st0 n ? n fp retreg y st1-7 n ? n y xmm0-7 n ? n y gs Thread ptr In the case where arguments are passed in registers, the arg1,2,3 registers are EAX, EDX, and ECX respectively. amd64-linux ~~~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? ------------------------------------------------------------------- rax n n int[63:0] retreg rbx y n y rcx n int#4 rdx n int#3 int[127:64] retreg rsi n int#2 y rdi n int#1 y rbp y n & guest state rsp reserved n/a n/a r8 n int#5 y r9 n int#6 y r10 n ? r11 n jmp temporary r12-15 y y eflags n n/a y st0-7 n n long double retreg y xmm0 n fp#1 fp retreg xmm1 n fp#2 fp-high retreg xmm2-7 n fp#3-8 y (3-7) xmm8-15 n y (8-12) fs thread ptr ppc32-linux ~~~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? ------------------------------------------------------------------- r0 n n sometimes RAZ r1 y n stack pointer r2 n n thread ptr r3 n int#1 int[31:0] retreg y r4 n int#2 also int retreg y r5 n int#3 y r6 n int#4 y r7 n int#5 y r8 n int#6 y r9 n int#7 y r10 n int#8 y r11 n y r12 n y r13 ? r14-28 y y r29 y reserved for dispatcher r30 y altivec spill temporary r31 y & guest state f0 n f1 n fp#1 fp retreg f2-8 n fp#2-8 f9-13 n f14-31 y y (14-21) v0-v19 ? v20-31 y y (20-27,29) cr0-7 lr y return address ctr n xer n fpscr ppc64-linux ~~~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? ------------------------------------------------------------------- r13 n n thread ptr TBD arm-linux ~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? -------------------------------------------------------------- r0 int#1 int[31:0] retreg? avail r1 int#2 int[63:32] retreg? avail r2 int#3 avail r3 int#4 avail r4 y avail r5 y avail r6 y avail r7 y avail r8 y GSP r9 y (but only on Linux; not in general) avail r10 y avail r11 y avail r12 possibly used by linker? unavail r13(sp) unavail r14(lr) unavail r15(pc) unavail cp15/c3/r2 thread ptr (see libvex_guest_arm.h, guest_TPIDRURO) VFP: d8-d15 are callee-saved r12 (IP) is probably available for use as a caller-saved register; but instead we use it as an intermediate for holding the address for F32/F64 spills, since the VFP load/store insns have reg+offset forms for offsets only up to 1020, which often isn't enough. arm64-linux ~~~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? --------------------------------------------------------------- r0 int#0 ret#0 (??) r1 int#1 ret#1 (??) r2-7 int#2..7 r8 "Indirect res loc reg" r9 "Temporary regs" chaining scratch r10-15 "Temporary regs" avail r16(IP0) r17(IP1) r18 "Platform reg" r19-20 "Temporary regs" r21 y "Callee saved" GSP r22-28 y "Callee saved" r29(FP) y r30(LR) y NZCV "Status register" Is there a TLS register? x21 is the GSP. x9 is a scratch chaining/spill temp. Neither are available to the register allocator. Q registers: It's a little awkward. Basically, D registers are the same as ARM, so d0-d7 and d16-d31 are caller-saved, but d8-d15 are callee-saved. Q registers are the same, except that the upper 64 bits of q8-q15 are caller-saved. The idea is that you only need to preserve D registers, not Q registers. s390x-linux ~~~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? -------------------------------------------------------------- r0 n see below unavail r1 n avail r2 n int#1 return value avail r3 n int#2 avail r4 n int#3 avail r5 n int#4 avail r6 y int#5 avail r7 y avail r8 y avail r9 y avail r10 y see below avail r11 y see below avail r12 y unavail VG_(dispatch_ctr) r13 y unavail gsp r14(lr) n unavail lr r15(sp) y unavail sp f0 n return value avail f1-f7 n avail f8-f11 y avail f12-f15 y see below avail a0 n thread ptr high word a1 n thread ptr low word When r0 is used as a base or index register its contents is ignored and the value 0 is used instead. This is the reason why VEX cannot use it. r10, r11 as well as f12-f15 are used as real regs during insn selection when register pairs are required. ppc32-aix5 ~~~~~~~~~~ Reg Callee Arg Name Saves? Reg? Comment Vex-uses? ------------------------------------------------------------------- r0 n n sometimes RAZ r1 y n stack pointer r2 n n TOC pointer r3 n int#1 int[31:0] retreg y r4 n int#2 also int retreg y r5 n int#3 y r6 n int#4 y r7 n int#5 y r8 n int#6 y r9 n int#7 y r10 n int#8 y r11 n "env pointer?!" y r12 n "exn handling" y r13 ? "reserved in 64-bit env" r14-28 y y r29 y reserved for dispatcher r30 y altivec spill temporary r31 y & guest state f0 n f1 n fp#1 fp retreg f2-13 n fp#2-13 f14-31 y y (14-21) v0-v19 ? v20-31 y y (20-27,29) cr0-7 lr y return address ctr n xer n fpscr