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.bouv...@linaro.org>
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
tcg/optimize.c | 42 +++++++++++++++++++++++++++---------------
1 file changed, 27 insertions(+), 15 deletions(-)
diff --git a/tcg/optimize.c b/tcg/optimize.c
index 453e8c43bd..6757fe0036 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -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;
--
2.43.0
