Commit 26d5b805 authored by Matthias Braun's avatar Matthias Braun
Browse files

improve our 'don't use AM' heuristic: immediates do not increase register pressure

parent f685f90e
......@@ -418,7 +418,8 @@ int ia32_is_non_address_mode_node(ir_node const *node)
}
/**
* Check if a given value is last used (i.e. die after) the block of some other node.
* Check if a given value is last used (i.e. die after) the block of some
* other node.
*/
static int value_last_used_here(be_lv_t *lv, ir_node *here, ir_node *value)
{
......@@ -441,6 +442,12 @@ static int value_last_used_here(be_lv_t *lv, ir_node *here, ir_node *value)
return 1;
}
static bool simple_is_immediate(const ir_node *node)
{
int symconsts = 0;
return do_is_immediate(node, &symconsts, false);
}
/**
* Walker: mark those nodes that cannot be part of an address mode because
* their value must be accessed through a register
......@@ -486,12 +493,17 @@ static void mark_non_address_nodes(ir_node *node, void *env)
left = get_binop_left(node);
right = get_binop_right(node);
/* Fold AM if any of the two operands does not die here. This duplicates
/* if any of the operands is an immediate then this will not
* increase register pressure */
if (simple_is_immediate(left) || simple_is_immediate(right))
return;
/* Fold AM if any of the two operands does not die here. This duplicates
* an addition and has the same register pressure for the case that only
* one operand dies, but is faster (on Pentium 4).
* && instead of || only folds AM if both operands do not die here */
if (!value_last_used_here(lv, node, left) ||
!value_last_used_here(lv, node, right)) {
!value_last_used_here(lv, node, right)) {
return;
}
......
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