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https://github.com/c64scene-ar/llvm-6502.git
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LLVM backend for 6502
ae6a305094
* Add support for promoting unions with fp values in them. This produces
our new int<->fp bitcast instructions, implementing
Transforms/ScalarRepl/union-fp-int.ll
As an example, this allows us to compile this:
union intfloat { int i; float f; };
float invsqrt(const float arg_x) {
union intfloat x = { .f = arg_x };
const float xhalf = arg_x * 0.5f;
x.i = 0x5f3759df - (x.i >> 1);
return x.f * (1.5f - xhalf * x.f * x.f);
}
into:
_invsqrt:
movss 4(%esp), %xmm0
movd %xmm0, %eax
sarl %eax
movl $1597463007, %ecx
subl %eax, %ecx
movd %ecx, %xmm1
mulss LCPI1_0, %xmm0
mulss %xmm1, %xmm0
movss LCPI1_1, %xmm2
mulss %xmm1, %xmm0
subss %xmm0, %xmm2
movl 8(%esp), %eax
mulss %xmm2, %xmm1
movss %xmm1, (%eax)
ret
instead of:
_invsqrt:
subl $4, %esp
movss 8(%esp), %xmm0
movss %xmm0, (%esp)
movl (%esp), %eax
movl $1597463007, %ecx
sarl %eax
subl %eax, %ecx
movl %ecx, (%esp)
mulss LCPI1_0, %xmm0
movss (%esp), %xmm1
mulss %xmm1, %xmm0
mulss %xmm1, %xmm0
movss LCPI1_1, %xmm2
subss %xmm0, %xmm2
mulss %xmm2, %xmm1
movl 12(%esp), %eax
movss %xmm1, (%eax)
addl $4, %esp
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32418 91177308-0d34-0410-b5e6-96231b3b80d8
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