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ARM back-end: Handle all possible immediates for ALU ops 

this patch handles all possible constants for immediate operand of ALU ops.
I'm not very satisfied by the implementation.

Laurent

Signed-off-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Andrzej Zaborowski <andrew.zaborowski@intel.com>
This commit is contained in:
Laurent Desnogues 2009-08-22 14:29:09 +02:00 committed by Andrzej Zaborowski
parent f878d2d235
commit 94953e6d74
1 changed files with 32 additions and 5 deletions
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37
tcg/arm/tcg-target.c
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@ -179,11 +179,36 @@ static int target_parse_constraint(TCGArgConstraint *ct, const char **pct_str)
return 0;
}
static inline uint32_t rotl(uint32_t val, int n)
{
return (val << n) | (val >> (32 - n));
}
/* ARM immediates for ALU instructions are made of an unsigned 8-bit
right-rotated by an even amount between 0 and 30. */
static inline int encode_imm(uint32_t imm)
{
/* simple case, only lower bits */
if ((imm & ~0xff) == 0)
return 0;
/* then try a simple even shift */
shift = ctz32(imm) & ~1;
if (((imm >> shift) & ~0xff) == 0)
return 32 - shift;
/* now try harder with rotations */
if ((rotl(imm, 2) & ~0xff) == 0)
return 2;
if ((rotl(imm, 4) & ~0xff) == 0)
return 4;
if ((rotl(imm, 6) & ~0xff) == 0)
return 6;
/* imm can't be encoded */
return -1;
}
static inline int check_fit_imm(uint32_t imm)
{
/* XXX: use rotation */
return (imm & ~0xff) == 0;
return encode_imm(imm) >= 0;
}
/* Test if a constant matches the constraint.
@ -1407,10 +1432,12 @@ static inline void tcg_out_op(TCGContext *s, int opc,
c = ARITH_EOR;
/* Fall through. */
gen_arith:
if (const_args[2])
if (const_args[2]) {
int rot;
rot = encode_imm(args[2]);
tcg_out_dat_imm(s, COND_AL, c,
args[0], args[1], args[2]);
else
args[0], args[1], rotl(args[2], rot) | (rot << 7));
} else
tcg_out_dat_reg(s, COND_AL, c,
args[0], args[1], args[2], SHIFT_IMM_LSL(0));
break;