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[lldb] Reland "Fix UB in half2float" to fix the ubsan bot. 

This relands part of the UB fix in 4b074b49be.
The original commit also added some additional tests that uncovered some
other issues (see D102845). I landed all the passing tests in
48780527dd and this patch is now just fixing
the UB in half2float. See D102846 for a proposed rewrite of the function.

Original commit message:

  The added DumpDataExtractorTest uncovered that this is lshifting a negative
  integer which upsets ubsan and breaks the sanitizer bot. This patch just
  changes the variable we shift to be unsigned.
This commit is contained in:
Raphael Isemann 2021-05-24 15:01:15 +02:00
parent 5ccc79dc38
commit 42a9c0c80c
1 changed files with 3 additions and 1 deletions
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4
lldb/source/Core/DumpDataExtractor.cpp
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@ -52,7 +52,9 @@ static float half2float(uint16_t half) {
float f;
uint32_t u;
} u;
int32_t v = (int16_t)half;
// Sign extend to 4 byte.
int32_t sign_extended = static_cast<int16_t>(half);
uint32_t v = static_cast<uint32_t>(sign_extended);
if (0 == (v & 0x7c00)) {
u.u = v & 0x80007FFFU;