https://bugs.llvm.org/show_bug.cgi?id=47431
Bug ID: 47431
Summary: Replace &a[x] - c * y with &a[x - y]
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
typedef __SIZE_TYPE__ size_t;
size_t a[64];
size_t* f(size_t b, size_t c)
{
return &a[b] + 1 * c;
}
size_t* g(size_t b, size_t c)
{
return &a[b + c];
}
size_t* fm(size_t b, size_t c)
{
return &a[b] - 1 * c;
}
size_t* gm(size_t b, size_t c)
{
return &a[b - c];
}
Clang:
f(unsigned long, unsigned long): # @f(unsigned
long, unsigned long)
shl rsi, 3
lea rax, [rsi + 8*rdi]
add rax, offset a
ret
g(unsigned long, unsigned long): # @g(unsigned
long, unsigned long)
add rdi, rsi
lea rax, [8*rdi + a]
ret
fm(unsigned long, unsigned long): # @fm(unsigned
long, unsigned long)
lea rax, [8*rdi + a]
shl rsi, 3
sub rax, rsi
ret
gm(unsigned long, unsigned long): # @gm(unsigned
long, unsigned long)
sub rdi, rsi
lea rax, [8*rdi + a]
ret
GCC:
f(unsigned long, unsigned long):
add rdi, rsi
lea rax, a[0+rdi*8]
ret
g(unsigned long, unsigned long):
add rdi, rsi
lea rax, a[0+rdi*8]
ret
fm(unsigned long, unsigned long):
sub rdi, rsi
lea rax, a[0+rdi*8]
ret
gm(unsigned long, unsigned long):
sub rdi, rsi
lea rax, a[0+rdi*8]
ret
ICC:
f(unsigned long, unsigned long):
add rdi, rsi #5.11
lea rax, QWORD PTR [a+rdi*8] #5.11
ret #5.11
g(unsigned long, unsigned long):
add rdi, rsi #10.17
lea rax, QWORD PTR [a+rdi*8] #10.11
ret
Godbolt:
https://godbolt.org/z/6W3rKd
--
You are receiving this mail because:
You are on the CC list for the bug._______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
