Hi Richard,
On Tue, Feb 09, 2016 at 04:50:52PM +0000, James Hogan wrote:
> > @@ -589,6 +608,50 @@ static void tcg_out_movi(TCGContext *s, TCGType type,
> > }
> > if (TCG_TARGET_REG_BITS == 32 || arg == (int32_t)arg) {
> > tcg_out_opc_imm(s, OPC_LUI, ret, TCG_REG_ZERO, arg >> 16);
> > + } else if (use_mips32r6_instructions) {
> > + tcg_target_long disp = arg - (intptr_t)s->code_ptr;
> > + if (disp == sextract32(disp, 2, 19) * 4) {
> > + tcg_out_opc_pc19(s, OPC_ADDIUPC, ret, disp >> 2);
> > + return;
> > + } else if ((disp & ~(tcg_target_long)0xffff)
> > + == sextract32(disp, 16, 16) * 0x10000) {
> > + tcg_out_opc_imm(s, OPC_ALUIPC, ret, 0, disp >> 16);
>
> I think ret and 0 are the wrong way around here. You're putting 0 in rs
> (the destination register), which causes a seg fault.
>
> OUT: [size=56]
> 0xfff30b0064: lw s1,-8(s0)
> 0xfff30b0068: bnezalc zero,s1,0xfff30b0090
> 0xfff30b006c: nop
> 0xfff30b0070: j 0xfff0000000
> 0xfff30b0074: nop
> 0xfff30b0078: lui s1,0xbfc0
> 0xfff30b007c: ori s1,s1,0x580
> 0xfff30b0080: sd s1,256(s0)
> 0xfff30b0084: aluipc zero,0xfeb7
> 0xfff30b0088: j 0xfff30b0034
> 0xfff30b008c: ori v0,v0,0x4010
> 0xfff30b0090: aluipc zero,0xfeb7
> 0xfff30b0094: j 0xfff30b0034
> 0xfff30b0098: ori v0,v0,0x4013
Actually, still not quite right.
ALUIPC does
dest <- ~0xffff & (PC + sign_extend(imm16<<16))
which is effectively
dest <- PC & ~0xffff + sign_extend(imm16<<16)
so disp should be between arg and code_ptr & ~0xffff, i.e. something
like this I think:
diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c
index 8205ea4e159f..9a5d31478797 100644
--- a/tcg/mips/tcg-target.c
+++ b/tcg/mips/tcg-target.c
@@ -666,12 +666,13 @@ static void tcg_out_movi(TCGContext *s, TCGType type,
tcg_out_opc_imm(s, OPC_LUI, ret, TCG_REG_ZERO, arg >> 16);
} else if (use_mips32r6_instructions) {
tcg_target_long disp = arg - (intptr_t)s->code_ptr;
+ tcg_target_long disphi = arg - ((intptr_t)s->code_ptr &
~(tcg_target_long)0xffff);
if (disp == sextract32(disp, 2, 19) * 4) {
tcg_out_opc_pc19(s, OPC_ADDIUPC, ret, disp >> 2);
return;
- } else if ((disp & ~(tcg_target_long)0xffff)
- == sextract32(disp, 16, 16) * 0x10000) {
- tcg_out_opc_imm(s, OPC_ALUIPC, 0, ret, disp >> 16);
+ } else if ((disphi & ~(tcg_target_long)0xffff)
+ == sextract32(disphi, 16, 16) * 0x10000) {
+ tcg_out_opc_imm(s, OPC_ALUIPC, 0, ret, disphi >> 16);
} else {
TCGReg in = TCG_REG_ZERO;
tcg_target_long tmp = (int16_t)arg;
Otherwise, in this case its trying to load the immediate 0xfff1c30000
relative to 0xfff30b0084, and calculates a disp of FEB7FF7C, which is
truncated to 0xFEB7. The result is then:
0xfff30b0000 + (int)0xfeb70000 = 0xfff1c20000
which is off by 64KiB.
With the above change we get:
disphi = 0xfeb80000
and the result is then:
0xfff30b0000 + (int)0xfeb80000 = 0xfff1c30000
Cheers
James
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