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POUse GCC generated assembler inside C++ Builder
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copied!<p>I'm using C++builder for GUI application on Win32. Borland compiler optimization is very bad and does not know how to use SSE. I have a function that is 5 times faster when compiled with mingw gcc 4.7. I think about asking gcc to generate assembler code and then use this cod inside my C function because Borland compiler allows inline assembler.</p> <p>The function in C looks like this :</p> <pre><code>void Test_Fn(double *x, size_t n,double *AV, size_t *mA, size_t NT) { double s = 77.777; size_t m = mA[NT-3]; AV[2]=x[n-4]+m*s; } </code></pre> <p>I made the function code very simple in order to simplify my question. My real function contains many loops.</p> <p>The Borland C++ compiler generated this assembler code :</p> <pre><code> ; ; void Test_Fn(double *x, size_t n,double *AV, size_t *mA, size_t NT) ; @1: push ebp mov ebp,esp add esp,-16 push ebx ; ; { ; double s = 77.777; ; mov dword ptr [ebp-8],1580547965 mov dword ptr [ebp-4],1079210426 ; ; size_t m = mA[NT-3]; ; mov edx,dword ptr [ebp+20] mov ecx,dword ptr [ebp+24] mov eax,dword ptr [edx+4*ecx-12] ; ; AV[2]=x[n-4]+m*s; ; ?live16385@48: ; EAX = m xor edx,edx mov dword ptr [ebp-16],eax mov dword ptr [ebp-12],edx fild qword ptr [ebp-16] mov ecx,dword ptr [ebp+8] mov ebx,dword ptr [ebp+12] mov eax,dword ptr [ebp+16] fmul qword ptr [ebp-8] fadd qword ptr [ecx+8*ebx-32] fstp qword ptr [eax+16] ; ; } ; ?live16385@64: ; @2: pop ebx mov esp,ebp pop ebp ret </code></pre> <p>While the gcc generated assembler code is :</p> <pre><code> _Test_Fn: mov edx, DWORD PTR [esp+20] mov eax, DWORD PTR [esp+16] mov eax, DWORD PTR [eax-12+edx*4] mov edx, DWORD PTR [esp+8] add eax, -2147483648 cvtsi2sd xmm0, eax mov eax, DWORD PTR [esp+4] addsd xmm0, QWORD PTR LC0 mulsd xmm0, QWORD PTR LC1 addsd xmm0, QWORD PTR [eax-32+edx*8] mov eax, DWORD PTR [esp+12] movsd QWORD PTR [eax+16], xmm0 ret LC0: .long 0 .long 1105199104 .align 8 LC1: .long 1580547965 .long 1079210426 .align 8 </code></pre> <p>I like to get help about how the function arguments acces is done in gcc and Borland C++. My function in C++ for Borland would be something like :</p> <pre><code> void Test_Fn(double *x, size_t n,double *AV, size_t *mA, size_t NT) { __asm { put gcc generated assembler here } } </code></pre> <p>Borland starts using <code>ebp</code> register while gcc use <code>esp</code> register. Can I force one of the compilers to generate compatible code for accessing the arguments using some calling conventions like cdecl ou stdcall ?</p>

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