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[mypyc] feat: optimize away first if-check in for_loop_helper_with_index #19933

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Merged
merged 3 commits into from
Sep 29, 2025
Merged

[mypyc] feat: optimize away first if-check in for_loop_helper_with_index #19933

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84e5c43
feat: optimize out first if-check in `for_loop_helper_with_index`
BobTheBuidler Sep 26, 2025
e3b3abc
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Sep 26, 2025
8607244
Merge branch 'master' into for-loop-helper-with-index
BobTheBuidler Sep 28, 2025
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7 changes: 6 additions & 1 deletion mypyc/irbuild/for_helpers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -183,7 +183,12 @@ def for_loop_helper_with_index(

builder.push_loop_stack(step_block, exit_block)

builder.goto_and_activate(condition_block)
if isinstance(length, Integer) and length.value > 0:
builder.goto(body_block)
builder.activate_block(condition_block)
else:
builder.goto_and_activate(condition_block)

for_gen.gen_condition()

builder.activate_block(body_block)
Expand Down
4 changes: 4 additions & 0 deletions mypyc/test-data/irbuild-lists.test
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Original file line number Diff line number Diff line change
Expand Up @@ -645,6 +645,7 @@ L0:
r0 = 'abc'
r1 = PyList_New(3)
r2 = 0
goto L2
L1:
r3 = r2 < 3 :: signed
if r3 goto L2 else goto L4 :: bool
Expand Down Expand Up @@ -690,6 +691,7 @@ L0:
r0 = 'abc'
r1 = PyList_New(3)
r2 = 0
goto L2
L1:
r3 = r2 < 3 :: signed
if r3 goto L2 else goto L4 :: bool
Expand Down Expand Up @@ -798,6 +800,7 @@ L0:
r0 = b'abc'
r1 = PyList_New(3)
r2 = 0
goto L2
L1:
r3 = r2 < 3 :: signed
if r3 goto L2 else goto L8 :: bool
Expand Down Expand Up @@ -952,6 +955,7 @@ L0:
r18 = CPyList_Extend(r10, r17)
r19 = PyList_New(13)
r20 = 0
goto L2
L1:
r21 = var_object_size r10
r22 = r20 < r21 :: signed
Expand Down
4 changes: 4 additions & 0 deletions mypyc/test-data/irbuild-tuple.test
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Original file line number Diff line number Diff line change
Expand Up @@ -417,6 +417,7 @@ L0:
r0 = 'abc'
r1 = PyTuple_New(3)
r2 = 0
goto L2
L1:
r3 = r2 < 3 :: signed
if r3 goto L2 else goto L4 :: bool
Expand Down Expand Up @@ -462,6 +463,7 @@ L0:
r0 = 'abc'
r1 = PyTuple_New(3)
r2 = 0
goto L2
L1:
r3 = r2 < 3 :: signed
if r3 goto L2 else goto L4 :: bool
Expand Down Expand Up @@ -570,6 +572,7 @@ L0:
r0 = b'abc'
r1 = PyTuple_New(3)
r2 = 0
goto L2
L1:
r3 = r2 < 3 :: signed
if r3 goto L2 else goto L8 :: bool
Expand Down Expand Up @@ -879,6 +882,7 @@ L0:
r18 = CPyList_Extend(r10, r17)
r19 = PyTuple_New(13)
r20 = 0
goto L2
L1:
r21 = var_object_size r10
r22 = r20 < r21 :: signed
Expand Down
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