https://bugs.llvm.org/show_bug.cgi?id=42983
Bug ID: 42983
Summary: Inefficient 64-bit absolute addresses in Cygwin
Product: clang
Version: 5.0
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: C++
Assignee: unassignedclangb...@nondot.org
Reporter: ag...@agner.org
CC: blitzrak...@gmail.com, dgre...@apple.com,
erik.pilking...@gmail.com, llvm-bugs@lists.llvm.org,
richard-l...@metafoo.co.uk
Cygwin Clang v. 5.0.1 is using 64-bit absolute addresses when accessing static
data in 64-bit mode. This is inefficient because it requires an extra 10-bytes
long instruction for loading an address into a register every time it needs to
access static data.
Linux Clang v. 6.0.0 with --target=x86_64-win64-windows gives the more
efficient relative addresses, as do all other compilers.
Is this a Cygwin-only issue? I posted it to the cygwin mailing list, but they
advised me to go here.
Test case:
#include <immintrin.h>
__m128d test (__m128d a) {
__m128d b = _mm_add_pd(a, _mm_set1_pd(1.5));
__m128d c = _mm_mul_pd(b, _mm_set1_pd(2.5));
return c;
}
Cygwin Clang assembly output:
_Z4testDv2_d:
vmovapd (%rcx), %xmm0
movabsq $.LCPI0_0, %rax
vaddpd (%rax), %xmm0, %xmm0
movabsq $.LCPI0_1, %rax
vmulpd (%rax), %xmm0, %xmm0
retq
Linux Clang assembly output with windows target:
"?test@@YAU__m128d@@U1@@Z": # @"\01?test@@YAU__m128d@@U1@@Z"
# %bb.0:
vmovapd (%rcx), %xmm0
vaddpd __xmm@3ff80000000000003ff8000000000000(%rip), %xmm0, %xmm0
vmulpd __xmm@40040000000000004004000000000000(%rip), %xmm0, %xmm0
retq
--
You are receiving this mail because:
You are on the CC list for the bug._______________________________________________
llvm-bugs mailing list
llvm-bugs@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
