[PATCH] D82129: [DebugInfo] Drop location ranges for variables which exist entirely outside the variable's scope

[Paul Robinson via Phabricator via llvm-commits]

probinson added a comment.

In D82129#2114150 <https://reviews.llvm.org/D82129#2114150>, @Orlando wrote:

> Looking closer at COFF/register-variables.ll, it doesn't look like a bug but instead another victim of how we model debug info. Before running -branch-folder (Control Flow Optimizer) all the instructions in the else block belong to the else block scope. The branch folder merges the common tails from 'then' and 'else' into 'else', merging the debug-locations while it does so. @jmorse summarised the situation well offline: Every time we call getMergedLocation, we are creating the conditions where this occurs, and eliminating it during compilation would be a high burden.


And yet, the variable was allocated to a register, and the variable's location information pointed to the correct instruction range.
Inadequacies in our ability to represent the scope properly shouldn't cause us to eliminate *correct* location information for variables.


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https://reviews.llvm.org/D82129