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From 363479b4d4f729959eafb1209d48ad75e928c00a Mon Sep 17 00:00:00 2001
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From: Aurelien Jarno <aurelien@aurel32.net>
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Date: Tue, 18 Sep 2012 19:12:36 +0200
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Subject: [PATCH] tcg/optimize: optimize "op r, a, a => movi r, 0"
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Now that it's possible to detect copies, we can optimize the case
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the "op r, a, a => movi r, 0". This helps in the computation of
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overflow flags when one of the two args is 0.
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Reviewed-by: Richard Henderson <rth@twiddle.net>
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Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
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Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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---
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tcg/optimize.c | 16 ++++++++++++++++
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1 file changed, 16 insertions(+)
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diff --git a/tcg/optimize.c b/tcg/optimize.c
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index b9a7da9..ceea644 100644
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--- a/tcg/optimize.c
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+++ b/tcg/optimize.c
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@@ -540,6 +540,22 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
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break;
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}
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+ /* Simplify expression for "op r, a, a => movi r, 0" cases */
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+ switch (op) {
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+ CASE_OP_32_64(sub):
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+ CASE_OP_32_64(xor):
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+ if (temps_are_copies(args[1], args[2])) {
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+ gen_opc_buf[op_index] = op_to_movi(op);
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+ tcg_opt_gen_movi(gen_args, args[0], 0);
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+ gen_args += 2;
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+ args += 3;
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+ continue;
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+ }
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+ break;
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+ default:
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+ break;
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+ }
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+
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/* Propagate constants through copy operations and do constant
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folding. Constants will be substituted to arguments by register
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allocator where needed and possible. Also detect copies. */
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--
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1.7.12.1
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