https://bugs.llvm.org/show_bug.cgi?id=41881
Bug ID: 41881
Summary: [DebugInfo@O2] SimplifyCFG sink splitting drops a
variable location
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Keywords: wrong-debug
Severity: normal
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: jeremy.morse.l...@gmail.com
CC: chackz0...@gmail.com, greg.bedw...@sony.com,
llvm-bugs@lists.llvm.org, orlando.hy...@sony.com,
paul.robin...@am.sony.com, stephen.to...@sony.com
Blocks: 38768
With llvm/clang r359863, running "clang -emit-llvm -O2 -g -S" on the code
below, the dbg.value representing the assignment of "local = q" is dropped by
SimplifyCFG. From the names of the basic blocks, it would appear to be the
SinkCommonCodeFromPredecessors function that does the dropping.
--------8<--------
volatile int g, *x;
int baz(int p, int q) {
int local;
local = p;
switch (g) {
case 1:
x[1] = local;
g += p;
break;
case 2:
x[1] += p;
break;
case 3:
local = q;
g++;
break;
}
return 4 + q;
}
-------->8--------
In this particular test case the impact of dropping the "local=q" assignment is
that the "local=p" assignment dominates all blocks, and an incorrect location
for "local" is produce in the "case 3" and exit block. (Didn't test this as far
as a debugger because I believe the error is fairly clear).
Referenced Bugs:
https://bugs.llvm.org/show_bug.cgi?id=38768
[Bug 38768] [meta][DebugInfo] Umbrella bug for poor debug experiences
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