Okay

Author: goldsteinn

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -590,18 +590,15 @@ static Instruction *foldCttzCtlz(IntrinsicInst &II, InstCombinerImpl &IC) {
 
   // cttz(Pow2) -> Log2(Pow2)
   // ctlz(Pow2) -> BitWidth - 1 - Log2(Pow2)
-  if (IsTZ) {
-    if (auto *R = IC.tryGetLog2(Op0, match(Op1, m_One()))) {
-      if (IsTZ)
-        return IC.replaceInstUsesWith(II, R);
-      BinaryOperator *BO = BinaryOperator::CreateSub(
-          ConstantInt::get(R->getType(),
-                           R->getType()->getScalarSizeInBits() - 1),
-          R);
-      BO->setHasNoSignedWrap();
-      BO->setHasNoUnsignedWrap();
-      return BO;
-    }
+  if (auto *R = IC.tryGetLog2(Op0, match(Op1, m_One()))) {
+    if (IsTZ)
+      return IC.replaceInstUsesWith(II, R);
+    BinaryOperator *BO = BinaryOperator::CreateSub(
+        ConstantInt::get(R->getType(), R->getType()->getScalarSizeInBits() - 1),
+        R);
+    BO->setHasNoSignedWrap();
+    BO->setHasNoUnsignedWrap();
+    return BO;
   }
 
   KnownBits Known = IC.computeKnownBits(Op0, 0, &II);

llvm/test/Transforms/InstCombine/cttz.ll

@@ -353,9 +353,8 @@ define i8 @fold_ctz_log2_maybe_z_okay(i8 %x, i8 %y, i1 %c) {
 
 define i8 @fold_clz_log2(i8 %x) {
 ; CHECK-LABEL: @fold_clz_log2(
-; CHECK-NEXT:    [[P2:%.*]] = shl nuw i8 1, [[X:%.*]]
-; CHECK-NEXT:    [[V:%.*]] = call i8 @llvm.umin.i8(i8 [[P2]], i8 32)
-; CHECK-NEXT:    [[R:%.*]] = call range(i8 2, 9) i8 @llvm.ctlz.i8(i8 [[V]], i1 true)
+; CHECK-NEXT:    [[TMP1:%.*]] = call i8 @llvm.umin.i8(i8 [[X:%.*]], i8 5)
+; CHECK-NEXT:    [[R:%.*]] = xor i8 [[TMP1]], 7
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %p2 = shl i8 1, %x
@@ -382,9 +381,8 @@ define i8 @fold_clz_log2_multiuse_fail(i8 %x) {
 
 define i9 @fold_clz_log2_i9(i9 %x) {
 ; CHECK-LABEL: @fold_clz_log2_i9(
-; CHECK-NEXT:    [[P2:%.*]] = shl nuw i9 1, [[X:%.*]]
-; CHECK-NEXT:    [[V:%.*]] = call i9 @llvm.umin.i9(i9 [[P2]], i9 32)
-; CHECK-NEXT:    [[R:%.*]] = call range(i9 3, 10) i9 @llvm.ctlz.i9(i9 [[V]], i1 true)
+; CHECK-NEXT:    [[TMP1:%.*]] = call i9 @llvm.umin.i9(i9 [[X:%.*]], i9 5)
+; CHECK-NEXT:    [[R:%.*]] = sub nuw nsw i9 8, [[TMP1]]
 ; CHECK-NEXT:    ret i9 [[R]]
 ;
   %p2 = shl i9 1, %x