我正在尝试在 32 位 centos6 上编译 webrtc 并出现以下错误。但这在 64 位 centos 上运行良好。有人可以帮助我吗？
row_gcc.cc:3574:4: error: ‘asm’ operand has impossible constraints
编译命令:
CXX obj/chromium/src/third_party/libyuv/source/libyuv.row_gcc.o
FAILED: obj/chromium/src/third_party/libyuv/source/libyuv.row_gcc.o
c++ -MMD -MF obj/chromium/src/third_party/libyuv/source/libyuv.row_gcc.o.d
-DV8_DEPRECATION_WARNINGS -D_FILE_OFFSET_BITS=64 -DCHROMIUM_BUILD
-DUI_COMPOSITOR_IMAGE_TRANSPORT -DUSE_AURA=1 -DUSE_PANGO=1 -DUSE_CAIRO=1
-DUSE_DEFAULT_RENDER_THEME=1 -DUSE_LIBJPEG_TURBO=1 -DUSE_X11=1
-DUSE_CLIPBOARD_AURAX11=1 -DENABLE_WEBRTC=1 -DENABLE_MEDIA_ROUTER=1
-DENABLE_PEPPER_CDMS -DENABLE_NOTIFICATIONS -DENABLE_TOPCHROME_MD=1
-DUSE_UDEV -DFIELDTRIAL_TESTING_ENABLED -DENABLE_TASK_MANAGER=1
-DENABLE_EXTENSIONS=1 -DENABLE_PDF=1 -DENABLE_PLUGINS=1
-DENABLE_SESSION_SERVICE=1 -DENABLE_THEMES=1 -DENABLE_PRINTING=1
-DENABLE_BASIC_PRINTING=1 -DENABLE_PRINT_PREVIEW=1 -DENABLE_SPELLCHECK=1
-DENABLE_CAPTIVE_PORTAL_DETECTION=1 -DENABLE_APP_LIST=1
-DENABLE_SETTINGS_APP=1 -DENABLE_SUPERVISED_USERS=1 -DENABLE_MDNS=1
-DENABLE_SERVICE_DISCOVERY=1 -DV8_USE_EXTERNAL_STARTUP_DATA
-DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL
-DHAVE_JPEG -DUSE_LIBPCI=1 -DUSE_GLIB=1 -DUSE_NSS_CERTS=1
-D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS
-DDYNAMIC_ANNOTATIONS_ENABLED=1 -DWTF_USE_DYNAMIC_ANNOTATIONS=1
-D_DEBUG -Igen
-I../../chromium/src/third_party/libyuv/include
-I../../chromium/src/third_party/libyuv
-I../../chromium/src/third_party/libjpeg_turbo -fstack-protector
--param=ssp-buffer-size=4 -pthread -fno-strict-aliasing -Wall -Wno-extra
-Wno-unused-parameter -Wno-missing-field-initializers -fvisibility=hidden
-pipe -fPIC
-B/home/test/webrtc-checkout/src/third_party/binutils/Linux_ia32/Release/bin
-Wno-unused-local-typedefs -msse2 -mfpmath=sse -mmmx -m32 -O0 -g
-funwind-tables -fno-exceptions -fno-rtti -fno-threadsafe-statics
-fvisibility-inlines-hidden
-std=gnu++11 -Wno-narrowing
-c ../../chromium/src/third_party/libyuv/source/row_gcc.cc
-o obj/chromium/src/third_party/libyuv/source/libyuv.row_gcc.o
../../chromium/src/third_party/libyuv/source/row_gcc.cc:
In function ‘void libyuv::BlendPlaneRow_SSSE3(const uint8*,
const uint8*, const uint8*, uint8*, int)’:
../../chromium/src/third_party/libyuv/source/row_gcc.cc:3574:4:
error: ‘asm’ operand has impossible constraints
海湾合作委员会版本:4.8.5
作为版本:GNU assembler (GNU Binutils) 2.26.20160125
third_party/binutils/Linux_ia32/Release/bin/as --version
GNU assembler (GNU Binutils) 2.26.20160125
Copyright (C) 2015 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or later.
This program has absolutely no warranty.
This assembler was configured for a target of `i686-pc-linux-gnu'.
chromium/src/third_party/libyuv/source/row_gcc.cc中的代码:
void BlendPlaneRow_SSSE3(const uint8* src0, const uint8* src1,
const uint8* alpha, uint8* dst, int width) {
asm volatile (
"pcmpeqb %%xmm5,%%xmm5 \n"
"psllw $0x8,%%xmm5 \n"
"mov $0x80808080,%%eax \n"
"movd %%eax,%%xmm6 \n"
"pshufd $0x0,%%xmm6,%%xmm6 \n"
"mov $0x807f807f,%%eax \n"
"movd %%eax,%%xmm7 \n"
"pshufd $0x0,%%xmm7,%%xmm7 \n"
"sub %2,%0 \n"
"sub %2,%1 \n"
"sub %2,%3 \n"
// 8 pixel loop.
LABELALIGN
"1: \n"
"movq (%2),%%xmm0 \n"
"punpcklbw %%xmm0,%%xmm0 \n"
"pxor %%xmm5,%%xmm0 \n"
"movq (%0,%2,1),%%xmm1 \n"
"movq (%1,%2,1),%%xmm2 \n"
"punpcklbw %%xmm2,%%xmm1 \n"
"psubb %%xmm6,%%xmm1 \n"
"pmaddubsw %%xmm1,%%xmm0 \n"
"paddw %%xmm7,%%xmm0 \n"
"psrlw $0x8,%%xmm0 \n"
"packuswb %%xmm0,%%xmm0 \n"
"movq %%xmm0,(%3,%2,1) \n"
"lea 0x8(%2),%2 \n"
"sub $0x8,%4 \n"
"jg 1b \n"
: "+r"(src0), // %0
"+r"(src1), // %1
"+r"(alpha), // %2
"+r"(dst), // %3
"+r"(width) // %4
:: "memory", "cc", "eax", "xmm0", "xmm1", "xmm2", "xmm5", "xmm6", "xmm7"
);
最佳答案
就像 David Wohlfred 所说的那样，问题是您的寄存器用完了。有 8 个通用寄存器，其中之一是 ESP，堆栈指针，永远不能用于满足约束。由于您正在编译的选项，另外两个寄存器 EBP 和 EBX 也不能用于满足约束。由于您在没有优化的情况下进行编译，因此 EBP 寄存器保留用于帧指针，并且由于您使用的是 -fPIC 标志，因此保留 EBX 寄存器以访问 GOT(全局对象表) .
所以留下五个寄存器可以用来满足寄存器约束，EAX、ECX、EDX、ESI和EDI。但是，您的 asm 语句破坏了 EAX，因此无法使用，只留下四个寄存器。 asm 语句有五个具有寄存器约束的操作数，这意味着它需要五个独立的寄存器，但只有四个可供编译器使用。所以约束是不可能满足的。
一个简单的解决方案是通过在 asm 语句中删除对 EAX 的使用来释放寄存器。该寄存器用于将两个不同的常量值加载到两个不同的 XMM 寄存器中。相反，可以直接从内存中加载常量。例如:
void BlendPlaneRow_SSSE3(const uint8* src0, const uint8* src1,
const uint8* alpha, uint8* dst, int width) {
static unsigned const __attribute__((aligned(4))) xmm6[4] = {
0x80808080, 0x80808080, 0x80808080, 0x80808080
};
static unsigned const __attribute__((aligned(4))) xmm7[4] = {
0x807f807f, 0x807f807f, 0x807f807f, 0x807f807f
};
asm volatile (
"pcmpeqb %%xmm5,%%xmm5 \n"
"psllw $0x8,%%xmm5 \n"
"movaps %5,%%xmm6 \n"
"movaps %6,%%xmm7 \n"
"sub %2,%0 \n"
"sub %2,%1 \n"
"sub %2,%3 \n"
// 8 pixel loop.
LABELALIGN
"1: \n"
"movq (%2),%%xmm0 \n"
"punpcklbw %%xmm0,%%xmm0 \n"
"pxor %%xmm5,%%xmm0 \n"
"movq (%0,%2,1),%%xmm1 \n"
"movq (%1,%2,1),%%xmm2 \n"
"punpcklbw %%xmm2,%%xmm1 \n"
"psubb %%xmm6,%%xmm1 \n"
"pmaddubsw %%xmm1,%%xmm0 \n"
"paddw %%xmm7,%%xmm0 \n"
"psrlw $0x8,%%xmm0 \n"
"packuswb %%xmm0,%%xmm0 \n"
"movq %%xmm0,(%3,%2,1) \n"
"lea 0x8(%2),%2 \n"
"sub $0x8,%4 \n"
"jg 1b \n"
: "+r"(src0), // %0
"+r"(src1), // %1
"+r"(alpha), // %2
"+r"(dst), // %3
"+r"(width) // %4
: "m" (xmm6),
"m" (xmm7)
: "memory", "cc", "xmm0", "xmm1", "xmm2", "xmm5", "xmm6", "xmm7"
);
}
更好的解决方案是重写它以使用内部函数并让编译器完成所有寄存器分配。
关于c++ - 错误 : ‘asm’ operand has impossible constraints when using gcc 32bit，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37494203/