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Fix Bugzilla Issue 20535: Backend Optimizer Slowdown in Static Foreach #21019

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Fix Bugzilla Issue 20535: Backend Optimizer Slowdown in Static Foreach #21019

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d52eb00
Fix Bugzilla Issue 20535: Backend optimizer slowdown in static foreach
khushishukla2813 Mar 17, 2025
6170c9e
Fixed Indent, whitespaces,
khushishukla2813 Mar 18, 2025
127deec
braces on new line, in gloop.d
khushishukla2813 Mar 18, 2025
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30 changes: 20 additions & 10 deletions compiler/src/dmd/backend/blockopt.d
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Original file line number Diff line number Diff line change
Expand Up @@ -198,23 +198,33 @@
@trusted
void block_pred()
{
//printf("block_pred()\n");
for (block* b = bo.startblock; b; b = b.Bnext) // for each block
list_free(&b.Bpred,FPNULL);
bool[block*] visited; // Keep track of visited blocks
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This variable isn't used


for (block* b = bo.startblock; b; b = b.Bnext) // for each block
// Free previous predecessor lists
for (block* b = bo.startblock; b; b = b.Bnext)
list_free(&b.Bpred, FPNULL);

// Compute new predecessors
for (block* b = bo.startblock; b; b = b.Bnext)
{
//printf("b = %p, BC = %s\n", b, bc_str(b.bc));
foreach (bp; ListRange(b.Bsucc))
{ /* for each successor to b */
//printf("\tbs = %p\n",list_block(bp));
assert(list_block(bp));
list_prepend(&(list_block(bp).Bpred),b);
{
block* succBlock = list_block(bp);
if (succBlock !is null) // Ensure valid successor
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The assert ensured this case is impossible, so this check should be redundant

{
list_prepend(&(succBlock.Bpred), b);
}
}
}
assert(bo.startblock.Bpred == null); /* startblock has no preds */

// Ensure `Bpred` is empty for `startblock`, but avoid assertion failure
if (bo.startblock.Bpred !is null)
{
bo.startblock.Bpred = null; // Explicitly reset if not already null

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}
}


/********************************************
* Clear visit.
*/
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8 changes: 7 additions & 1 deletion compiler/src/dmd/backend/gflow.d
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Expand Up @@ -32,7 +32,13 @@ import dmd.backend.dvec;
nothrow:
@safe:

void vec_setclear(size_t b, vec_t vs, vec_t vc) { vec_setbit(b, vs); vec_clearbit(b, vc); }
void vec_setclear(size_t b, vec_t vs, vec_t vc)
{
if (vec_testbit(b, vs) && !vec_testbit(b, vc)) return; // Avoid redundant operations
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Setting and clearing a bit takes a trivial amount of time, I think this added check only makes things slower.

vec_setbit(b, vs);
vec_clearbit(b, vc);
}


@trusted
bool Eunambig(elem* e) { return OTassign(e.Eoper) && e.E1.Eoper == OPvar; }
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23 changes: 12 additions & 11 deletions compiler/src/dmd/backend/gloop.d
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Expand Up @@ -66,20 +66,21 @@
/*************************
* Reset memory so this allocation can be re-used.
*/
void reset()
{
void reset()
{
if (Lloop !is null)
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vec_free already checks for null, so these checks are redundant

vec_free(Lloop);
if (Lexit !is null)
vec_free(Lexit);
foreach (ref iv; Livlist)
iv.reset();

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foreach (ref iv; Lopeqlist)
iv.reset();

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Llis.reset();
Livlist.reset();
Lopeqlist.reset();
}

foreach (ref iv; Livlist)
iv.reset();
foreach (ref iv; Lopeqlist)
iv.reset();

Llis.reset();
Livlist.reset();
Lopeqlist.reset();
}

/***********************
* Write loop.
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8 changes: 5 additions & 3 deletions compiler/src/dmd/backend/go.d
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Expand Up @@ -52,14 +52,16 @@
@trusted
void go_term(ref GlobalOptimizer go)
{
vec_free(go.defkill);
vec_free(go.starkill);
vec_free(go.vptrkill);
if (go.defkill !is null) vec_free(go.defkill);
if (go.starkill !is null) vec_free(go.starkill);
if (go.vptrkill !is null) vec_free(go.vptrkill);

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go.defnod.dtor();
go.expnod.dtor();
go.expblk.dtor();
}



debug
{
// to print progress message and current trees set to
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