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tcg/optimize: Split out fold_affected_mask

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There are only a few logical operations which can compute
an "affected" mask.  Split out handling of this optimization
to a separate function, only to be called when applicable.

Remove the a_mask field from OptContext, as the mask is
no longer stored anywhere.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2024-12-19 10:33:51 -08:00
parent 1526855c01
commit 045ace35a8
1 changed files with 27 additions and 15 deletions
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42
tcg/optimize.c
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@ -64,7 +64,6 @@ typedef struct OptContext {
QSIMPLEQ_HEAD(, MemCopyInfo) mem_free;
/* In flight values from optimization. */
uint64_t a_mask; /* mask bit is 0 iff value identical to first input */
uint64_t z_mask; /* mask bit is 0 iff value bit is 0 */
uint64_t s_mask; /* mask of clrsb(value) bits */
TCGType type;
@ -1047,7 +1046,6 @@ static bool fold_const2_commutative(OptContext *ctx, TCGOp *op)
static bool fold_masks(OptContext *ctx, TCGOp *op)
{
uint64_t a_mask = ctx->a_mask;
uint64_t z_mask = ctx->z_mask;
uint64_t s_mask = ctx->s_mask;
@ -1059,7 +1057,6 @@ static bool fold_masks(OptContext *ctx, TCGOp *op)
* type changing opcodes.
*/
if (ctx->type == TCG_TYPE_I32) {
a_mask = (int32_t)a_mask;
z_mask = (int32_t)z_mask;
s_mask |= MAKE_64BIT_MASK(32, 32);
ctx->z_mask = z_mask;
@ -1069,6 +1066,19 @@ static bool fold_masks(OptContext *ctx, TCGOp *op)
if (z_mask == 0) {
return tcg_opt_gen_movi(ctx, op, op->args[0], 0);
}
return false;
}
/*
* An "affected" mask bit is 0 if and only if the result is identical
* to the first input. Thus if the entire mask is 0, the operation
* is equivalent to a copy.
*/
static bool fold_affected_mask(OptContext *ctx, TCGOp *op, uint64_t a_mask)
{
if (ctx->type == TCG_TYPE_I32) {
a_mask = (uint32_t)a_mask;
}
if (a_mask == 0) {
return tcg_opt_gen_mov(ctx, op, op->args[0], op->args[1]);
}
@ -1305,8 +1315,9 @@ static bool fold_and(OptContext *ctx, TCGOp *op)
* Known-zeros does not imply known-ones. Therefore unless
* arg2 is constant, we can't infer affected bits from it.
*/
if (arg_is_const(op->args[2])) {
ctx->a_mask = z1 & ~z2;
if (arg_is_const(op->args[2]) &&
fold_affected_mask(ctx, op, z1 & ~z2)) {
return true;
}
return fold_masks(ctx, op);
@ -1331,7 +1342,9 @@ static bool fold_andc(OptContext *ctx, TCGOp *op)
*/
if (arg_is_const(op->args[2])) {
uint64_t z2 = ~arg_info(op->args[2])->z_mask;
ctx->a_mask = z1 & ~z2;
if (fold_affected_mask(ctx, op, z1 & ~z2)) {
return true;
}
z1 &= z2;
}
ctx->z_mask = z1;
@ -1709,8 +1722,8 @@ static bool fold_extract(OptContext *ctx, TCGOp *op)
z_mask_old = arg_info(op->args[1])->z_mask;
z_mask = extract64(z_mask_old, pos, len);
if (pos == 0) {
ctx->a_mask = z_mask_old ^ z_mask;
if (pos == 0 && fold_affected_mask(ctx, op, z_mask_old ^ z_mask)) {
return true;
}
ctx->z_mask = z_mask;
ctx->s_mask = smask_from_zmask(z_mask);
@ -1777,8 +1790,8 @@ static bool fold_exts(OptContext *ctx, TCGOp *op)
ctx->z_mask = z_mask;
ctx->s_mask = s_mask;
if (!type_change) {
ctx->a_mask = s_mask & ~s_mask_old;
if (!type_change && fold_affected_mask(ctx, op, s_mask & ~s_mask_old)) {
return true;
}
return fold_masks(ctx, op);
@ -1819,8 +1832,8 @@ static bool fold_extu(OptContext *ctx, TCGOp *op)
ctx->z_mask = z_mask;
ctx->s_mask = smask_from_zmask(z_mask);
if (!type_change) {
ctx->a_mask = z_mask_old ^ z_mask;
if (!type_change && fold_affected_mask(ctx, op, z_mask_old ^ z_mask)) {
return true;
}
return fold_masks(ctx, op);
}
@ -2482,8 +2495,8 @@ static bool fold_sextract(OptContext *ctx, TCGOp *op)
s_mask |= MAKE_64BIT_MASK(len, 64 - len);
ctx->s_mask = s_mask;
if (pos == 0) {
ctx->a_mask = s_mask & ~s_mask_old;
if (pos == 0 && fold_affected_mask(ctx, op, s_mask & ~s_mask_old)) {
return true;
}
return fold_masks(ctx, op);
@ -2843,7 +2856,6 @@ void tcg_optimize(TCGContext *s)
}
/* Assume all bits affected, no bits known zero, no sign reps. */
ctx.a_mask = -1;
ctx.z_mask = -1;
ctx.s_mask = 0;