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target/mips: Fix JALS32/J32 instruction handling for microMIPS 

microMIPS J & JAL instructions perform a jump in a 128MB region and 5
top bits of the address need to be preserved. This is different behavior
compared to standard mips systems, where the jump is executed within a
256MB region.
Note that microMIPS32 instruction set documentation appears to have
inconsistent information regarding JALX32 instruction - it is written in
the doc that:

"To execute a procedure call within the current 256 MB-aligned region
(...)
The low 26 bits of the target address is the target field shifted left
2 bits."

But the target address is already 26 bits. Moreover, the operation
description indicates that 28 bits are copied, so the statement about
use of 26 bits is _most likely_ incorrect and the corresponding code
remains the same as for standard mips instruction set.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@fungible.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230216051717.3911212-2-marcin.nowakowski@fungible.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
This commit is contained in:
Marcin Nowakowski 2023-02-16 06:17:14 +01:00 committed by Philippe Mathieu-Daudé
parent a43972e176
commit 9055ffd76e
1 changed files with 8 additions and 0 deletions
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8
target/mips/tcg/translate.c
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@ -4887,6 +4887,14 @@ static void gen_compute_branch(DisasContext *ctx, uint32_t opc,
break;
case OPC_J:
case OPC_JAL:
{
/* Jump to immediate */
int jal_mask = ctx->hflags & MIPS_HFLAG_M16 ? 0xF8000000
: 0xF0000000;
btgt = ((ctx->base.pc_next + insn_bytes) & jal_mask)
| (uint32_t)offset;
break;
}
case OPC_JALX:
/* Jump to immediate */
btgt = ((ctx->base.pc_next + insn_bytes) & (int32_t)0xF0000000) |