GCC and the Multiply Instruction

I am using GCC in 32-bit mode on a Windows 7 machine under cygwin. I have the following function:

  unsigned f1(unsigned x, unsigned y)
      return x*y;

I want the code to do an unsigned multiply and as such I would expect it to generate the mul instruction, not the imul instruction. I compile the program with the following command:

 gcc -m32 -S t4.c

The generated assembly code is:

     .file   "t4.c"
     .globl  _f1
     .def    _f1;    .scl    2;  .type   32; .endef
     pushl   %ebp
     movl    %esp, %ebp
     movl    8(%ebp), %eax
     imull   12(%ebp), %eax
     popl    %ebp
    .ident  "GCC: (GNU) 4.8.2"

I believe that the generated code has the wrong multiply instruction in it but I find it hard to believe that GCC has such a simple bug. Please comment.


The compiler relies on the "as-if" rule: No standard conforming program can detect a difference between what this program does and what the program should do, since the lowest 32 bits of the result are the same for both instructions.

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