[LLVMbugs] [Bug 13265] New: __builtin_expect generates bad code
bugzilla-daemon at llvm.org
bugzilla-daemon at llvm.org
Tue Jul 3 17:27:01 PDT 2012
http://llvm.org/bugs/show_bug.cgi?id=13265
Bug #: 13265
Summary: __builtin_expect generates bad code
Product: clang
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
AssignedTo: unassignedclangbugs at nondot.org
ReportedBy: nwmcsween at gmail.com
CC: llvmbugs at cs.uiuc.edu
Classification: Unclassified
When using __builtin_expect() llvm erroneously aligns both branches.
Files and llvm / gcc output is here: https://gist.github.com/3043849 (I was
comparing output)
>From top to bottom of items in that link:
1. gcc asm diff output between readdir.c and readdir_o.c
2. gcc asm of readdir.c
3. gcc asm of readdir_o.c
4. llvm asm of readdir.c
5. llvm asm of readdir_o.c
6. readdir.c
7. llvm asm diff output between readdir.c and readdir_o.c
8. readdir_o.c
A testcase would be anything that uses __builtint_expect
clang version 3.2 (/var/cache/paludis/distfiles/scm/clang
7f0873c1c99276f05eab992c57be2f84adc58e40)
(/var/cache/paludis/distfiles/scm/llvm
2b409b65d45e2857dd842afc18b6b8c2da791a35)
Target: x86_64-pc-linux-gnu
Thread model: posix
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