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From a0b71ad6a3f8aeb8b5ea6d112a7afeadc7c004a4 Mon Sep 17 00:00:00 2001
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From: Aurelien Jarno <aurelien@aurel32.net>
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Date: Wed, 19 Sep 2012 22:00:22 +0200
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Subject: [PATCH] tcg/optimize: prefer the "op a, a, b" form for commutative
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ops
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The "op a, a, b" form is better handled on non-RISC host than the "op
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a, b, a" form, so swap the arguments to this form when possible, and
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when b is not a constant.
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This reduces the number of generated instructions by a tiny bit.
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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 | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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diff --git a/tcg/optimize.c b/tcg/optimize.c
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index abe016a..c8ae50b 100644
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--- a/tcg/optimize.c
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+++ b/tcg/optimize.c
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@@ -434,7 +434,10 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
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CASE_OP_32_64(eqv):
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CASE_OP_32_64(nand):
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CASE_OP_32_64(nor):
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- if (temps[args[1]].state == TCG_TEMP_CONST) {
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+ /* Prefer the constant in second argument, and then the form
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+ op a, a, b, which is better handled on non-RISC hosts. */
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+ if (temps[args[1]].state == TCG_TEMP_CONST || (args[0] == args[2]
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+ && temps[args[2]].state != TCG_TEMP_CONST)) {
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tmp = args[1];
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args[1] = args[2];
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args[2] = tmp;
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