https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70131
Bug ID: 70131
Summary: PowerPC ISA 2.07 is inefficient at doint
(float)(int)x.
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: meissner at gcc dot gnu.org
Target Milestone: ---
The current GCC compiler does not use the vupkhsw instruction that was
introduced in ISA 2.07 (power8) to sign extend the 32-bit integer to 64-bit
integer. Instead it does a store and then a load to sign extend the value.
The code:
double foo (double x) { return (double)(int)x; }
generates the following code for power8:
fctiwz 1,1
addi 9,1,-16
stfiwx 1,0,9
ori 2,2,0
lfiwax 1,0,9
fcfid 1,1
It does this because
It should generate something like:
xscvdpsxws 33,1
vupkhsw 1,1
xxpermdi 33,33,33,2
xscvsxddp 1,33
