Fix float-to-integer conversion for wide destination types#8986
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tautschnig wants to merge 1 commit intodiffblue:developfrom
Open
Fix float-to-integer conversion for wide destination types#8986tautschnig wants to merge 1 commit intodiffblue:developfrom
tautschnig wants to merge 1 commit intodiffblue:developfrom
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float_bvt::to_integer did not extend the fraction to dest_width before shifting, causing incorrect results when dest_width exceeds the fraction width (the shift distance went negative for large exponents). Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
tautschnig
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kroening,
martin-cs and
peterschrammel
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Pull request overview
Note
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Fixes incorrect float-to-integer conversion when the destination integer width exceeds the float fraction width by extending the fraction before shifting and adding a regression test.
Changes:
- Extend
unpacked.fractiontodest_width(when needed) before computing the shift for integer conversion. - Adjust the shift offset computation to use the effective fraction width.
- Add regression tests covering wide float-to-int conversions (bitvector + SMT paths).
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| src/solvers/floatbv/float_bv.cpp | Extends fraction width before shifting to avoid negative/incorrect shift distances for wide integer targets. |
| regression/cbmc/Float-to-int-wide/main.c | Adds a regression program exercising float-to-(wide)int conversions. |
| regression/cbmc/Float-to-int-wide/test.desc | Adds a FloatBV regression test harness entry. |
| regression/cbmc/Float-to-int-wide/test_smt.desc | Adds an SMT regression test harness entry for the same scenario. |
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Comment on lines
+409
to
410
| exprt offset = from_integer(effective_width - 1, signedbv_typet(spec.e)); | ||
| const minus_exprt distance(offset, unpacked.exponent); |
Comment on lines
+48
to
+54
| __CPROVER_assume(e == 3000000000.0f); // 3 billion, fits in unsigned | ||
| unsigned int r5 = (unsigned int)e; | ||
| // 3000000000.0f is exactly 0x1.6bcc41p+31 = 3000000000 (exact) | ||
| // Actually 3e9 rounds to 3000000000 in float? Let's check: | ||
| // 3000000000 = 0xB2D05E00, float: 0x1.65a0bcp+31 = 2999999488 | ||
| // Use an exact value instead. | ||
| __CPROVER_assume(e == 16777216.0f); |
| // needs the full 32-bit integer range. | ||
|
|
||
| #include <assert.h> | ||
| #include <limits.h> |
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## develop #8986 +/- ##
===========================================
+ Coverage 80.50% 80.52% +0.02%
===========================================
Files 1704 1704
Lines 188796 188805 +9
Branches 73 73
===========================================
+ Hits 151993 152044 +51
+ Misses 36803 36761 -42 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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float_bvt::to_integer did not extend the fraction to dest_width before shifting, causing incorrect results when dest_width exceeds the fraction width (the shift distance went negative for large exponents).