Converts a floating-point operand to a 32-bit signed integer, rounding the result towards 0.
| Bits | Value |
|---|---|
| 0-5 | 63 |
| 6-10 | FRT |
| 11-15 | /// |
| 16-20 | FRB |
| 21-30 | 15 |
| 31 | Rc |
| PowerPC | |
|---|---|
| fctiwz | FRT, FRB |
| fctiwz. | FRT, FRB |
| POWER2 | |
|---|---|
| fcirz | FRT, FRB |
| fcirz. | FRT, FRB |
The fctiwz and fcirz instructions convert the floating-point operand in floating-point register (FPR) FRB to a 32-bit, signed, fixed-point integer, rounding the operand toward 0. The result is placed in bits 32-63 of FPR FRT. Bits 0-31 of FPR FRT are undefined.
If the operand in FPR FRB is greater than 231 - 1, then the bits 32-63 of FPR FRT are set to 0x7FFF FFFF. If the operand in FPR FRB is less than -231, then the bits 32-63 of FPR FRT are set to 0x8000 0000.
The fctiwz and fcirz instructions each have two syntax forms. Each syntax form has a different effect on Condition Register Field 1.
| Syntax Form | Floating-Point Status and Control Register | Record Bit (Rc) | Condition Register Field 1 |
| fctiwz | C,FL,FG,FE,FU,FR,FI,FX,XX,VXCVI, VXSNAN | 0 | None |
| fctiwz. | C,FL,FG,FE,FU,FR,FI,FX,XX,VXCVI, VXSNAN | 1 | FX,FEX,VX,OX |
| fcirz | C,FL,FG,FE,FU,FR,FI,FX,XX,VXCVI, VXSNAN | 0 | None |
| fcirz. | C,FL,FG,FE,FU,FR,FI,FX,XX,VXCVI, VXSNAN | 1 | FX,FEX,VX,OX |
The syntax forms of the fctiwz and fcirz instructions always affect the Floating-Point Status and Control Register. If the syntax form sets the Record (Rc) bit to 1, the instruction affects the Floating-Point Exception (FX), Floating-Point Enabled Exception (FEX), Floating-Point Invalid Operation Exception (VX), and Floating-Point Overflow Exception (OX) bits in Condition Register Field 1. FPSCR(C,FI,FG,FE,FU) are undefined.
| FRT | Specifies the floating-point register where the integer result is placed. |
| FRB | Specifies the source floating-point register for the floating-point operand. |
The following code adds a floating-point value to an array element selected based on a second floating-point value. If value2 is greater than or equal to n, but less than n+1, add value1 to the nth element of the array:
# Assume GPR 4 contains the address of the first element of
# the array.
# Assume GPR 1 contains the stack pointer.
# Assume a doubleword TEMP variable is allocated on the stack
# for use by the conversion routine.
# Assume FPR 6 contains value2.
# Assume FPR 4 contains value1.
fctiwz 5,6 # Convert value2 to integer.
stfd 5,TEMP(1) # Store to temp location.
lwz 3,TEMP+4(1) # Get the integer part of the
# doubleword.
lfdx 5,3,4 # Get the selected array element.
fadd 5,5,4 # Add value1 to array element.
stfd 5,3,4 # Save the new value of the
# array element.
Floating-Point Arithmetic Instructions .
Interpreting the Contents of a Floating-Point Register .