mirror of https://github.com/proxmox/mirror_qemu
tcg/arm: Reduce vector alignment requirement for NEON
With arm32, the ABI gives us 8-byte alignment for the stack.
While it's possible to realign the stack to provide 16-byte alignment,
it's far easier to simply not encode 16-byte alignment in the
VLD1 and VST1 instructions that we emit.
Remove the assertion in temp_allocate_frame, limit natural alignment
to the provided stack alignment, and add a comment.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1999878
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210912174925.200132-1-richard.henderson@linaro.org>
Message-Id: <20211206191335.230683-2-richard.henderson@linaro.org>
(cherry picked from commit b9537d5904
)
Signed-off-by: Michael Roth <michael.roth@amd.com>
parent
e88636b4d4
commit
711bd602cc
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@ -2477,8 +2477,13 @@ static void tcg_out_ld(TCGContext *s, TCGType type, TCGReg arg,
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tcg_out_vldst(s, INSN_VLD1 | 0x7d0, arg, arg1, arg2);
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return;
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case TCG_TYPE_V128:
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/* regs 2; size 8; align 16 */
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tcg_out_vldst(s, INSN_VLD1 | 0xae0, arg, arg1, arg2);
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/*
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* We have only 8-byte alignment for the stack per the ABI.
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* Rather than dynamically re-align the stack, it's easier
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* to simply not request alignment beyond that. So:
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* regs 2; size 8; align 8
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*/
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tcg_out_vldst(s, INSN_VLD1 | 0xad0, arg, arg1, arg2);
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return;
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default:
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g_assert_not_reached();
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@ -2497,8 +2502,8 @@ static void tcg_out_st(TCGContext *s, TCGType type, TCGReg arg,
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tcg_out_vldst(s, INSN_VST1 | 0x7d0, arg, arg1, arg2);
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return;
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case TCG_TYPE_V128:
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/* regs 2; size 8; align 16 */
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tcg_out_vldst(s, INSN_VST1 | 0xae0, arg, arg1, arg2);
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/* See tcg_out_ld re alignment: regs 2; size 8; align 8 */
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tcg_out_vldst(s, INSN_VST1 | 0xad0, arg, arg1, arg2);
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return;
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default:
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g_assert_not_reached();
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@ -3060,7 +3060,13 @@ static void temp_allocate_frame(TCGContext *s, TCGTemp *ts)
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g_assert_not_reached();
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}
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assert(align <= TCG_TARGET_STACK_ALIGN);
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/*
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* Assume the stack is sufficiently aligned.
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* This affects e.g. ARM NEON, where we have 8 byte stack alignment
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* and do not require 16 byte vector alignment. This seems slightly
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* easier than fully parameterizing the above switch statement.
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*/
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align = MIN(TCG_TARGET_STACK_ALIGN, align);
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off = ROUND_UP(s->current_frame_offset, align);
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/* If we've exhausted the stack frame, restart with a smaller TB. */
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