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70 lines
1.5 KiB
Plaintext
70 lines
1.5 KiB
Plaintext
//===---------------------------------------------------------------------===//
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// Random ideas for the X86 backend: MMX-specific stuff.
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//===---------------------------------------------------------------------===//
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//===---------------------------------------------------------------------===//
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This:
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#include <mmintrin.h>
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__v2si qux(int A) {
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return (__v2si){ 0, A };
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}
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is compiled into:
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_qux:
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subl $28, %esp
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movl 32(%esp), %eax
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movd %eax, %mm0
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movq %mm0, (%esp)
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movl (%esp), %eax
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movl %eax, 20(%esp)
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movq %mm0, 8(%esp)
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movl 12(%esp), %eax
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movl %eax, 16(%esp)
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movq 16(%esp), %mm0
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addl $28, %esp
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ret
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Yuck!
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GCC gives us:
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_qux:
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subl $12, %esp
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movl 16(%esp), %eax
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movl 20(%esp), %edx
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movl $0, (%eax)
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movl %edx, 4(%eax)
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addl $12, %esp
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ret $4
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//===---------------------------------------------------------------------===//
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int main() {
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__m64 A[1] = { _mm_cvtsi32_si64(1) };
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__m64 B[1] = { _mm_cvtsi32_si64(10) };
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__m64 sum = _mm_cvtsi32_si64(0);
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sum = __builtin_ia32_paddq(__builtin_ia32_paddq(A[0], B[0]), sum);
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printf("Sum = %d\n", _mm_cvtsi64_si32(sum));
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return 0;
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}
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Generates:
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movl $11, %eax
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### movd %eax, %mm0
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### movq %mm0, 8(%esp)
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### movl 8(%esp), %eax
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movl %eax, 4(%esp)
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movl $_str, (%esp)
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call L_printf$stub
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xorl %eax, %eax
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addl $28, %esp
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These instructions are unnecessary.
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