https://llvm.org/bugs/show_bug.cgi?id=26969
Bug ID: 26969
Summary: FP exception when optimized; code relocation
implicated
Product: clang
Version: 3.7
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: richard.bra...@autodesk.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 16047
--> https://llvm.org/bugs/attachment.cgi?id=16047&action=edit
Source code, Makefile, README.TXT explaining issue.
You guys do great work!
Floating point exception due to unexpected code relocation, for all
optimization
levels greater than -O0.
This occurs in a C translation of the Fortran LAPACK numerical library.
We show a floating point overflow runtime exception which occurs due to
pre-evaluation of the expression "bignum * cnorm" in line 258 of dlaln2.c.
The overflow occurs because the cnorm variable is greater than 1. A following
if test checks the value of cnorm and should prevent the multiplication when
cnorm is greater than 1.
We'd like to know the LLVM compiler team's opinions:
* Is this a compiler bug? It seems that way to us. Previous versions of Xcode
did not produce the exception. We're using Xcode 7.1.
* If this is not a compiler bug, what is the rationale for allowing code
relocations which disregard tests of the operands?
* Is there a compiler command line option which we can set to disable the
specific optimization which causes the code relocation?
THANKS!!
Rich Brandt
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