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evan implemented this.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47948 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2008-03-05 17:11:51 +00:00
parent 6af4a751a2
commit 4d93b2f16d
1 changed files with 0 additions and 26 deletions
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26
lib/Target/X86/README-SSE.txt
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@ -586,32 +586,6 @@ ABS/NEG/copysign etc.
//===---------------------------------------------------------------------===//
"converting 64-bit constant pool entry to 32-bit not necessarily beneficial"
http://llvm.org/PR1264
For this test case:
define double @foo(double %x) {
%y = mul double %x, 5.000000e-01
ret double %y
}
llc -march=x86-64 currently produces a 32-bit constant pool entry and this code:
cvtss2sd .LCPI1_0(%rip), %xmm1
mulsd %xmm1, %xmm0
instead of just using a 64-bit constant pool entry with this:
mulsd .LCPI1_0(%rip), %xmm0
This is due to the code in ExpandConstantFP in LegalizeDAG.cpp. It notices that
x86-64 indeed has an instruction to load a 32-bit float from memory and convert
it into a 64-bit float in a register, however it doesn't notice that this isn't
beneficial because it prevents the load from being folded into the multiply.
//===---------------------------------------------------------------------===//
These functions:
#include <xmmintrin.h>