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3-460 Vol. 2A IMUL—Signed Multiply
INSTRUCTION SET REFERENCE, A-M
ELSE IF (NumberOfOperands
= 2)
THEN
temp ← DEST ∗ SRC (* Signed multiplication; temp is double DEST size *)
DEST ← DEST ∗ SRC (* Signed multiplication *)
IF temp
≠ DEST
THEN CF ← 1; OF ← 1;
ELSE CF ← 0; OF ← 0; FI;
ELSE (* NumberOfOperands
= 3 *)
DEST ← SRC1 ∗ SRC2 (* Signed multiplication *)
temp ← SRC1 ∗ SRC2 (* Signed multiplication; temp is double SRC1 size *)
IF temp
≠ DEST
THEN CF ← 1; OF ← 1;
ELSE CF ← 0; OF ← 0; FI;
FI;
FI;
Flags Affected
For the one operand form of the instruction, the CF and OF flags are set when signif-
icant bits are carried into the upper half of the result and cleared when the result fits
exactly in the lower half of the result. For the two- and three-operand forms of the
instruction, the CF and OF flags are set when the result must be truncated to fit in the
destination operand size and cleared when the result fits exactly in the destination
operand size. The SF, ZF, AF, and PF flags are undefined.
Protected Mode Exceptions
#GP(0) If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.
If the DS, ES, FS, or GS register is used to access memory and it
contains a NULL NULL segment selector.
#SS(0) If a memory operand effective address is outside the SS
segment limit.
#PF(fault-code) If a page fault occurs.
#AC(0) If alignment checking is enabled and an unaligned memory
reference is made while the current privilege level is 3.
#UD If the LOCK prefix is used.
Real-Address Mode Exceptions
#GP If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.