https://bugs.llvm.org/show_bug.cgi?id=41150
Bug ID: 41150
Summary: [SimplifyLibCalls] bad codegen for bcmp with constant
inputs
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: clement.cour...@gmail.com
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org
Example: (https://gcc.godbolt.org/z/pfvPCB)
#include <cstring>
static constexpr char k[] = "ABCDEFGH";
int F(char* p) {
return memcmp(p, k, strlen(k)) == 0;
}
With clang 7, -O2:
F(char*): # @F(char*)
movabs rcx, 5208208757389214273
xor eax, eax
cmp qword ptr [rdi], rcx
sete al
ret
With trunk, -O2:
F(char*): # @F(char*)
push rax
mov esi, offset k
mov edx, 8
call bcmp
xor ecx, ecx
test eax, eax
sete cl
mov eax, ecx
pop rcx
ret
k:
.asciz "ABCDEFGH"
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