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[PATCH 4/4] tcg/optimize: optimize TSTNE using smask and zmask
From: |
Paolo Bonzini |
Subject: |
[PATCH 4/4] tcg/optimize: optimize TSTNE using smask and zmask |
Date: |
Wed, 28 Feb 2024 12:11:51 +0100 |
Generalize the existing optimization of "TSTNE x,sign" and "TSTNE x,-1".
This can be useful in some cases when the i386 frontend creates opcodes
that test against 0xff or 0x80.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
tcg/optimize.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/tcg/optimize.c b/tcg/optimize.c
index 752cc5c56b6..ab976a5bbe7 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -793,6 +793,7 @@ static int do_constant_folding_cond1(OptContext *ctx, TCGOp
*op, TCGArg dest,
TCGArg *p1, TCGArg *p2, TCGArg *pcond)
{
TCGCond cond;
+ TempOptInfo *i1;
bool swap;
int r;
@@ -810,19 +811,21 @@ static int do_constant_folding_cond1(OptContext *ctx,
TCGOp *op, TCGArg dest,
return -1;
}
+ i1 = arg_info(*p1);
+
/*
* TSTNE x,x -> NE x,0
- * TSTNE x,-1 -> NE x,0
+ * TSTNE x,i -> NE x,0 if i includes all nonzero bits of x
*/
- if (args_are_copies(*p1, *p2) || arg_is_const_val(*p2, -1)) {
+ if (args_are_copies(*p1, *p2) ||
+ (arg_is_const(*p2) && (i1->z_mask & ~arg_info(*p2)->val) == 0)) {
*p2 = arg_new_constant(ctx, 0);
*pcond = tcg_tst_eqne_cond(cond);
return -1;
}
- /* TSTNE x,sign -> LT x,0 */
- if (arg_is_const_val(*p2, (ctx->type == TCG_TYPE_I32
- ? INT32_MIN : INT64_MIN))) {
+ /* TSTNE x,i -> LT x,0 if i only includes sign bit copies */
+ if (arg_is_const(*p2) && (arg_info(*p2)->val & ~i1->s_mask) == 0) {
*p2 = arg_new_constant(ctx, 0);
*pcond = tcg_tst_ltge_cond(cond);
return -1;
--
2.43.2