r

Author: AZero13

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -20233,10 +20233,6 @@ bool ARMTargetLowering::targetShrinkDemandedConstant(
     }
   }
 
-  // Don't optimize if it is legal already.
-  if (isLegalLogicalImmediate(Mask, Subtarget))
-    return false;
-
   if (isLegalLogicalImmediate(ShrunkMask, Subtarget)) {
     ++NumOptimizedImms;
     return UseMask(ShrunkMask);
@@ -20247,6 +20243,13 @@ bool ARMTargetLowering::targetShrinkDemandedConstant(
     return UseMask(ExpandedMask);
   }
 
+  // Don't optimize if it is legal already.
+  if (isLegalLogicalImmediate(Mask, Subtarget))
+    return false;
+
+  if (isLegalLogicalImmediate(~Mask, Subtarget))
+    return UseMask(Mask); // FIXME: Returning false causes infinite loop.
+
   // Potential improvements:
   //
   // We could try to recognize lsls+lsrs or lsrs+lsls pairs here.

llvm/test/CodeGen/Thumb/bic_imm.ll

@@ -76,21 +76,21 @@ define void @truncated_neg256(i16 %a, ptr %p) {
 ; CHECK-T1-LABEL: truncated_neg256:
 ; CHECK-T1:       @ %bb.0:
 ; CHECK-T1-NEXT:    movs r2, #255
-; CHECK-T1-NEXT:    bics r0, r2
-; CHECK-T1-NEXT:    strh r0, [r1]
+; CHECK-T1-NEXT:    lsls r2, r2, #8
+; CHECK-T1-NEXT:    ands r2, r0
+; CHECK-T1-NEXT:    strh r2, [r1]
 ; CHECK-T1-NEXT:    bx lr
 ;
 ; CHECK-T2-LABEL: truncated_neg256:
 ; CHECK-T2:       @ %bb.0:
-; CHECK-T2-NEXT:    bic r0, r0, #255
+; CHECK-T2-NEXT:    and r0, r0, #65280
 ; CHECK-T2-NEXT:    strh r0, [r1]
 ; CHECK-T2-NEXT:    bx lr
   %and = and i16 %a, -256
   store i16 %and, ptr %p
   ret void
 }
 
-; FIXME: Thumb2 supports "bic r0, r0, #510"
 define void @truncated_neg511(i16 %a, ptr %p) {
 ; CHECK-T1-LABEL: truncated_neg511:
 ; CHECK-T1:       @ %bb.0:
@@ -105,8 +105,7 @@ define void @truncated_neg511(i16 %a, ptr %p) {
 ;
 ; CHECK-T2-LABEL: truncated_neg511:
 ; CHECK-T2:       @ %bb.0:
-; CHECK-T2-NEXT:    movw r2, #65025
-; CHECK-T2-NEXT:    ands r0, r2
+; CHECK-T2-NEXT:    bic r0, r0, #510
 ; CHECK-T2-NEXT:    strh r0, [r1]
 ; CHECK-T2-NEXT:    bx lr
   %and = and i16 %a, -511