https://bugs.llvm.org/show_bug.cgi?id=50392
Bug ID: 50392
Summary: Compiler no longer producing single horizontal add
instruction after ab2c499d
Product: new-bugs
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: douglas_y...@playstation.sony.com
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org
One of our internal tests compiles the following code and verifies that it
generates a horizontal add instruction in the resulting assembly when
optimizations are enabled and targeting btver2.
__attribute__((noinline))
__m256d add_pd_002(__m256d a, __m256d b) {
__m256d r = (__m256d){ a[0] + a[1], a[2] + a[3], b[0] + b[1], b[2] + b[3] };
return __builtin_shufflevector(r, a, 0, -1, 2, 3);
}
Prior to commit ab2c499, when compiled with "-g0 -O3 -march=btver2", the
compiler would produce the following code:
vinsertf128 $1, %xmm1, %ymm0, %ymm0
vhaddpd %ymm1, %ymm0, %ymm0
But following the mentioned change, the compiler is now producing the following
code instead:
vextractf128 $1, %ymm1, %xmm2
vhaddpd %xmm0, %xmm0, %xmm0
vhaddpd %xmm2, %xmm1, %xmm1
vperm2f128 $2, %ymm0, %ymm1, %ymm0 # ymm0 = ymm0[0,1],ymm1[0,1]
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