compiler alias analysis: Fix repeated argument bug #9356
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When the same variable occurs multiple times in the argument list to a call, that variable should become aliased. This patch corrects the above described omission by renaming the current aa_alias_surviving_args/4 to aa_alias_surviving_phi_args/4 which we use for Phi-instructions and creating a new aa_alias_surviving_args/4 (for calls) which makes use of aa_alias_surviving_phi_args/4 but also does a second pass through the argument list to find repeated variables.
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bjorng
previously approved these changes
Jan 29, 2025
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Of note is that, although the alias analysis was wrong, actual cases where the bug led to bad code seem very infrequent. For example, running |
bjorng
approved these changes
Jan 30, 2025
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When the same variable occurs multiple times in the argument list to a call, that variable should become aliased.
This patch corrects the above described omission by renaming the current aa_alias_surviving_args/4 to aa_alias_surviving_phi_args/4 which we use for Phi-instructions and creating a new aa_alias_surviving_args/4 (for calls) which makes use of aa_alias_surviving_phi_args/4 but also does a second pass through the argument list to find repeated variables.
This patch is made against OTP-27.2.1 (the bug first appeared in OTP-27), the same functional change should also be pulled into master, where it doesn't apply cleanly. This branch contains the same change, but rebased to the current master.