Summary:
This can be used to optimize large multiplications after legalization.
Depends on D29565
Reviewers: mkuper, spatel, RKSimon, zvi, bkramer, aaboud, craig.topper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29587
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296711
91177308-0d34-0410-b5e6-
96231b3b80d8
return OFK_Never;
}
+ // mulhi + 1 never overflow
+ if (N0.getOpcode() == ISD::UMUL_LOHI && N0.getResNo() == 1 &&
+ (~N1Zero & 0x01) == ~N1Zero)
+ return OFK_Never;
+
+ if (N1.getOpcode() == ISD::UMUL_LOHI && N1.getResNo() == 1) {
+ APInt N0Zero, N0One;
+ computeKnownBits(N0, N0Zero, N0One);
+
+ if ((~N0Zero & 0x01) == ~N0Zero)
+ return OFK_Never;
+ }
+
return OFK_Sometime;
}
; X64-NEXT: movq %rdi, %rax
; X64-NEXT: mulq %rsi
; X64-NEXT: andl $1, %ecx
-; X64-NEXT: addq %rdx, %rcx
-; X64-NEXT: sbbq %rdx, %rdx
-; X64-NEXT: andl $1, %edx
-; X64-NEXT: movq %rcx, %rax
+; X64-NEXT: leaq (%rcx,%rdx), %rax
+; X64-NEXT: xorl %edx, %edx
; X64-NEXT: retq
%1 = zext i64 %a to i128
%2 = zext i64 %b to i128