diff --git a/llvm/lib/Target/X86/README.txt b/llvm/lib/Target/X86/README.txt index 551d9f08526b..a7a477d2d5b8 100644 --- a/llvm/lib/Target/X86/README.txt +++ b/llvm/lib/Target/X86/README.txt @@ -1884,3 +1884,40 @@ _add32carry: ret //===---------------------------------------------------------------------===// + +This: +char t(char c) { + return c/3; +} + +Compiles to: $clang t.c -S -o - -O3 -mkernel -fomit-frame-pointer + +_t: ## @t + movslq %edi, %rax + imulq $-1431655765, %rax, %rcx ## imm = 0xFFFFFFFFAAAAAAAB + shrq $32, %rcx + addl %ecx, %eax + movl %eax, %ecx + shrl $31, %ecx + shrl %eax + addl %ecx, %eax + movsbl %al, %eax + ret + +GCC gets: + +_t: + movl $86, %eax + imulb %dil + shrw $8, %ax + sarb $7, %dil + subb %dil, %al + movsbl %al,%eax + ret + +which is nicer. This also happens for int, not just char. + +//===---------------------------------------------------------------------===// + + +