https://bugs.llvm.org/show_bug.cgi?id=42673
Bug ID: 42673
Summary: Missed optimization: division reminder
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: zamazan...@tut.by
CC: llvm-bugs@lists.llvm.org, neeil...@live.com,
richard-l...@metafoo.co.uk
For the code below clang(trunk) with -O3:
int DivRem(int a, int b, int* result)
{
int div = a / b;
*result = a - (div * b);
return div;
}
produces this:
DivRem(int, int, int*): # @DivRem(int, int, int*)
mov rcx, rdx
mov eax, edi
cdq
idiv esi
imul esi, eax
sub edi, esi
mov dword ptr [rcx], edi
ret
but gcc(trunk) with -O3 produces this:
DivRem(int, int, int*):
mov eax, edi
mov r8, rdx
cdq
idiv esi
mov DWORD PTR [r8], edx
ret
I think we can do in LLVM as GCC.
P.S. Compiler explorer example: https://godbolt.org/z/RryrJw
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