https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80275
Bug ID: 80275
Summary: Poor (but valid) code generated by optimizer passing
optimizer list to function
Product: gcc
Version: 6.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: cuzdav at gmail dot com
Target Milestone: ---
Codegen regression from the 5.x series of g++. After 6.1, g++ produces poor
code for f2() below, when it should be identical to f1().
Command line: g++ -O2 -v -std=c++14 minbad.cpp
// minbad.cpp
#include <algorithm>
int g() {
return 1234;
}
int f1() {
return std::min(std::min(1, g()), 4);
}
int f2() {
return std::min({1, g(), 4});
}
The actual disassembly looks like this:
g():
mov eax, 1234
ret
f1():
mov eax, 1
ret
f2():
lea rsi, [rsp-24]
lea rax, [rsp-24]
mov DWORD PTR [rsp-24], 1
mov DWORD PTR [rsp-20], 1234
mov DWORD PTR [rsp-16], 4
lea rcx, [rsi+12]
lea rdx, [rax+4]
mov eax, 1
.L4:
add rdx, 4
cmp rdx, rcx
je .L3
.L8:
cmp eax, DWORD PTR [rdx]
jle .L4
mov eax, DWORD PTR [rdx]
add rdx, 4
cmp rdx, rcx
jne .L8
.L3:
rep ret
Compiler Info (this is not a mac-specific problem.)
-------------
g++-6 -v -std=c++14 /tmp/minbad.cpp
Using built-in specs.
COLLECT_GCC=g++-6
COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc/6.3.0_1/libexec/gcc/x86_64-apple-darwin16.3.0/6.3.0/lto-wrapper
Target: x86_64-apple-darwin16.3.0
Configured with: ../configure --build=x86_64-apple-darwin16.3.0
--prefix=/usr/local/Cellar/gcc/6.3.0_1
--libdir=/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6
--enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-6
--with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr
--with-mpc=/usr/local/opt/libmpc --with-isl=/usr/local/opt/isl
--with-system-zlib --enable-libstdcxx-time=yes --enable-stage1-checking
--enable-checking=release --enable-lto --with-build-config=bootstrap-debug
--disable-werror --with-pkgversion='Homebrew GCC 6.3.0_1'
--with-bugurl=https://github.com/Homebrew/homebrew-core/issues --enable-plugin
--disable-nls --enable-multilib
Thread model: posix
gcc version 6.3.0 (Homebrew GCC 6.3.0_1)
COLLECT_GCC_OPTIONS='-v' '-std=c++14' '-mmacosx-version-min=10.12.4'
'-asm_macosx_version_min=10.12' '-shared-libgcc' '-mtune=core2'
/usr/local/Cellar/gcc/6.3.0_1/libexec/gcc/x86_64-apple-darwin16.3.0/6.3.0/cc1plus
-quiet -v -D__DYNAMIC__ /tmp/minbad.cpp -fPIC -quiet -dumpbase minbad.cpp
-mmacosx-version-min=10.12.4 -mtune=core2 -auxbase minbad -std=c++14 -version
-o /var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//cc9vAOcI.s
GNU C++14 (Homebrew GCC 6.3.0_1) version 6.3.0 (x86_64-apple-darwin16.3.0)
compiled by GNU C version 6.3.0, GMP version 6.1.2, MPFR version 3.1.5,
MPC version 1.0.3, isl version 0.15
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory
"/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/../../../../../../x86_64-apple-darwin16.3.0/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/../../../../../../include/c++/6.3.0
/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/../../../../../../include/c++/6.3.0/x86_64-apple-darwin16.3.0
/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/../../../../../../include/c++/6.3.0/backward
/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/include
/usr/local/include
/usr/local/Cellar/gcc/6.3.0_1/include
/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/include-fixed
/usr/include
/System/Library/Frameworks
/Library/Frameworks
End of search list.
GNU C++14 (Homebrew GCC 6.3.0_1) version 6.3.0 (x86_64-apple-darwin16.3.0)
compiled by GNU C version 6.3.0, GMP version 6.1.2, MPFR version 3.1.5,
MPC version 1.0.3, isl version 0.15
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 61c7027fd27bf9cda4c9b1dfc6e5d124
COLLECT_GCC_OPTIONS='-v' '-std=c++14' '-mmacosx-version-min=10.12.4'
'-shared-libgcc' '-mtune=core2'
as -arch x86_64 -v -force_cpusubtype_ALL -mmacosx-version-min=10.12 -o
/var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//ccipBAqo.o
/var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//cc9vAOcI.s
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin16.4.0
Thread model: posix
InstalledDir:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
"/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang"
-cc1as -triple x86_64-apple-macosx10.12.0 -filetype obj -main-file-name
cc9vAOcI.s -target-cpu penryn -fdebug-compilation-dir /tmp
-dwarf-debug-producer Apple LLVM version 8.0.0 (clang-800.0.42.1)
-dwarf-version=2 -mrelocation-model pic -o
/var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//ccipBAqo.o
/var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//cc9vAOcI.s
COMPILER_PATH=/usr/local/Cellar/gcc/6.3.0_1/libexec/gcc/x86_64-apple-darwin16.3.0/6.3.0/:/usr/local/Cellar/gcc/6.3.0_1/libexec/gcc/x86_64-apple-darwin16.3.0/6.3.0/:/usr/local/Cellar/gcc/6.3.0_1/libexec/gcc/x86_64-apple-darwin16.3.0/:/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/:/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/
LIBRARY_PATH=/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/:/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/../../../
COLLECT_GCC_OPTIONS='-v' '-std=c++14' '-mmacosx-version-min=10.12.4'
'-shared-libgcc' '-mtune=core2'
/usr/local/Cellar/gcc/6.3.0_1/libexec/gcc/x86_64-apple-darwin16.3.0/6.3.0/collect2
-dynamic -arch x86_64 -macosx_version_min 10.12.4 -weak_reference_mismatches
non-weak -o a.out
-L/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0
-L/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/../../..
/var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//ccipBAqo.o -lstdc++
-no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v
collect2 version 6.3.0
/usr/bin/ld -dynamic -arch x86_64 -macosx_version_min 10.12.4
-weak_reference_mismatches non-weak -o a.out
-L/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0
-L/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0/../../..
/var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//ccipBAqo.o -lstdc++
-no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v
@(#)PROGRAM:ld PROJECT:ld64-274.2
configured to support archs: armv6 armv7 armv7s arm64 i386 x86_64 x86_64h
armv6m armv7k armv7m armv7em (tvOS)
Library search paths:
/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6/gcc/x86_64-apple-darwin16.3.0/6.3.0
/usr/local/Cellar/gcc/6.3.0_1/lib/gcc/6
/usr/lib
/usr/local/lib
Framework search paths:
/Library/Frameworks/
/System/Library/Frameworks/
/usr/local/bin/gnm -n
/var/folders/d_/97dm5hss6cq7y8jlfxh3k6xrsw2_zt/T//ccipBAqo.o
