https://llvm.org/bugs/show_bug.cgi?id=31144
Bug ID: 31144
Summary: [ppc] Convert char/short to double through memory
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Backend: PowerPC
Assignee: unassignedb...@nondot.org
Reporter: car...@google.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Compile following code with options -m64 -O2
extern void bar(double);
void foo(char* p)
{
bar(*p);
}
void foo1(unsigned short* p)
{
bar(*p);
}
LLVM generates:
.Lfunc_lep0:
.localentry foo, .Lfunc_lep0-.Lfunc_gep0
# BB#0: # %entry
mflr 0
std 31, -8(1)
std 0, 16(1)
stdu 1, -112(1)
lbz 3, 0(3) // load original value
mr 31, 1
addi 4, 31, 100
stw 3, 100(31) // store
ori 2, 2, 0
lxsiwzx 0, 0, 4 // load
xscvuxddp 1, 0
bl bar
nop
addi 1, 1, 112
ld 0, 16(1)
ld 31, -8(1)
mtlr 0
blr
Note that lxsiwzx is immediately following stw, they access the same memory, it
is very slow. Instruction mtvsrwz can be used to move a value from integer
register to VSX register directly.
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