summaryrefslogtreecommitdiff
path: root/arch/i386/math-emu/reg_u_mul.S
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/i386/math-emu/reg_u_mul.S
downloadconfigs-2.6.12-rc2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/i386/math-emu/reg_u_mul.S')
-rw-r--r--arch/i386/math-emu/reg_u_mul.S148
1 files changed, 148 insertions, 0 deletions
diff --git a/arch/i386/math-emu/reg_u_mul.S b/arch/i386/math-emu/reg_u_mul.S
new file mode 100644
index 00000000000..973f12af97d
--- /dev/null
+++ b/arch/i386/math-emu/reg_u_mul.S
@@ -0,0 +1,148 @@
+ .file "reg_u_mul.S"
+/*---------------------------------------------------------------------------+
+ | reg_u_mul.S |
+ | |
+ | Core multiplication routine |
+ | |
+ | Copyright (C) 1992,1993,1995,1997 |
+ | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ | E-mail billm@suburbia.net |
+ | |
+ | |
+ +---------------------------------------------------------------------------*/
+
+/*---------------------------------------------------------------------------+
+ | Basic multiplication routine. |
+ | Does not check the resulting exponent for overflow/underflow |
+ | |
+ | FPU_u_mul(FPU_REG *a, FPU_REG *b, FPU_REG *c, unsigned int cw); |
+ | |
+ | Internal working is at approx 128 bits. |
+ | Result is rounded to nearest 53 or 64 bits, using "nearest or even". |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "fpu_emu.h"
+#include "control_w.h"
+
+
+
+#ifndef NON_REENTRANT_FPU
+/* Local storage on the stack: */
+#define FPU_accum_0 -4(%ebp) /* ms word */
+#define FPU_accum_1 -8(%ebp)
+
+#else
+/* Local storage in a static area: */
+.data
+ .align 4,0
+FPU_accum_0:
+ .long 0
+FPU_accum_1:
+ .long 0
+#endif /* NON_REENTRANT_FPU */
+
+
+.text
+ENTRY(FPU_u_mul)
+ pushl %ebp
+ movl %esp,%ebp
+#ifndef NON_REENTRANT_FPU
+ subl $8,%esp
+#endif /* NON_REENTRANT_FPU */
+
+ pushl %esi
+ pushl %edi
+ pushl %ebx
+
+ movl PARAM1,%esi
+ movl PARAM2,%edi
+
+#ifdef PARANOID
+ testl $0x80000000,SIGH(%esi)
+ jz L_bugged
+ testl $0x80000000,SIGH(%edi)
+ jz L_bugged
+#endif /* PARANOID */
+
+ xorl %ecx,%ecx
+ xorl %ebx,%ebx
+
+ movl SIGL(%esi),%eax
+ mull SIGL(%edi)
+ movl %eax,FPU_accum_0
+ movl %edx,FPU_accum_1
+
+ movl SIGL(%esi),%eax
+ mull SIGH(%edi)
+ addl %eax,FPU_accum_1
+ adcl %edx,%ebx
+/* adcl $0,%ecx // overflow here is not possible */
+
+ movl SIGH(%esi),%eax
+ mull SIGL(%edi)
+ addl %eax,FPU_accum_1
+ adcl %edx,%ebx
+ adcl $0,%ecx
+
+ movl SIGH(%esi),%eax
+ mull SIGH(%edi)
+ addl %eax,%ebx
+ adcl %edx,%ecx
+
+ /* Get the sum of the exponents. */
+ movl PARAM6,%eax
+ subl EXP_BIAS-1,%eax
+
+ /* Two denormals can cause an exponent underflow */
+ cmpl EXP_WAY_UNDER,%eax
+ jg Exp_not_underflow
+
+ /* Set to a really low value allow correct handling */
+ movl EXP_WAY_UNDER,%eax
+
+Exp_not_underflow:
+
+/* Have now finished with the sources */
+ movl PARAM3,%edi /* Point to the destination */
+ movw %ax,EXP(%edi)
+
+/* Now make sure that the result is normalized */
+ testl $0x80000000,%ecx
+ jnz LResult_Normalised
+
+ /* Normalize by shifting left one bit */
+ shll $1,FPU_accum_0
+ rcll $1,FPU_accum_1
+ rcll $1,%ebx
+ rcll $1,%ecx
+ decw EXP(%edi)
+
+LResult_Normalised:
+ movl FPU_accum_0,%eax
+ movl FPU_accum_1,%edx
+ orl %eax,%eax
+ jz L_extent_zero
+
+ orl $1,%edx
+
+L_extent_zero:
+ movl %ecx,%eax
+ jmp fpu_reg_round
+
+
+#ifdef PARANOID
+L_bugged:
+ pushl EX_INTERNAL|0x205
+ call EXCEPTION
+ pop %ebx
+ jmp L_exit
+
+L_exit:
+ popl %ebx
+ popl %edi
+ popl %esi
+ leave
+ ret
+#endif /* PARANOID */
+