Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3445,22 +3445,14 @@
 
     bool Signed = II->getIntrinsicID() == Intrinsic::amdgcn_sbfe;
 
-    // TODO: Also emit sub if only width is constant.
-    if (!CWidth && COffset && Offset == 0) {
-      Constant *KSize = ConstantInt::get(COffset->getType(), IntSize);
-      Value *ShiftVal = Builder.CreateSub(KSize, II->getArgOperand(2));
-      ShiftVal = Builder.CreateZExt(ShiftVal, II->getType());
-
-      Value *Shl = Builder.CreateShl(Src, ShiftVal);
-      Value *RightShift = Signed ? Builder.CreateAShr(Shl, ShiftVal)
-                                 : Builder.CreateLShr(Shl, ShiftVal);
-      RightShift->takeName(II);
-      return replaceInstUsesWith(*II, RightShift);
-    }
-
     if (!CWidth || !COffset)
       break;
 
+    // The case of Width == 0 is handled above, which makes this tranformation
+    // safe.  If Width == 0, then the ashr and lshr instructions become poison
+    // value since the shift amount would be equal to the bit size.
+    assert (Width != 0);
+
     // TODO: This allows folding to undef when the hardware has specific
     // behavior?
     if (Offset + Width < IntSize) {
Index: test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
===================================================================
--- test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
+++ test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
@@ -934,32 +934,23 @@
 }
 
 ; CHECK-LABEL: @ubfe_offset_0(
-; CHECK-NEXT: %1 = sub i32 32, %width
-; CHECK-NEXT: %2 = lshr i32 -1, %1
-; CHECK-NEXT: %bfe = and i32 %2, %src
-; CHECK-NEXT: ret i32 %bfe
+; CHECK-NEXT: %bfe = call i32 @llvm.amdgcn.ubfe.i32(i32 %src, i32 0, i32 %width)
 define i32 @ubfe_offset_0(i32 %src, i32 %width) {
   %bfe = call i32 @llvm.amdgcn.ubfe.i32(i32 %src, i32 0, i32 %width)
   ret i32 %bfe
 }
 
 ; CHECK-LABEL: @ubfe_offset_32(
-; CHECK-NEXT: %1 = sub i32 32, %width
-; CHECK-NEXT: %2 = lshr i32 -1, %1
-; CHECK-NEXT: %bfe = and i32 %2, %src
-; CHECK-NEXT: ret i32 %bfe
+; CHECK-NEXT: %bfe = call i32 @llvm.amdgcn.ubfe.i32(i32 %src, i32 0, i32 %width)
 define i32 @ubfe_offset_32(i32 %src, i32 %width) {
   %bfe = call i32 @llvm.amdgcn.ubfe.i32(i32 %src, i32 32, i32 %width)
   ret i32 %bfe
 }
 
 ; CHECK-LABEL: @ubfe_offset_31(
-; CHECK-NEXT: %1 = sub i32 32, %width
-; CHECK-NEXT: %2 = lshr i32 -1, %1
-; CHECK-NEXT: %bfe = and i32 %2, %src
-; CHECK-NEXT: ret i32 %bfe
+; CHECK-NEXT: %bfe = call i32 @llvm.amdgcn.ubfe.i32(i32 %src, i32 31, i32 %width)
 define i32 @ubfe_offset_31(i32 %src, i32 %width) {
-  %bfe = call i32 @llvm.amdgcn.ubfe.i32(i32 %src, i32 32, i32 %width)
+  %bfe = call i32 @llvm.amdgcn.ubfe.i32(i32 %src, i32 31, i32 %width)
   ret i32 %bfe
 }
 
@@ -1040,11 +1031,7 @@
 }
 
 ; CHECK-LABEL: @ubfe_offset_0_i64(
-; CHECK-NEXT: %1 = sub i32 64, %width
-; CHECK-NEXT: %2 = zext i32 %1 to i64
-; CHECK-NEXT: %3 = lshr i64 -1, %2
-; CHECK-NEXT: %bfe = and i64 %3, %src
-; CHECK-NEXT: ret i64 %bfe
+; CHECK-NEXT: %bfe = call i64 @llvm.amdgcn.ubfe.i64(i64 %src, i32 0, i32 %width)
 define i64 @ubfe_offset_0_i64(i64 %src, i32 %width) {
   %bfe = call i64 @llvm.amdgcn.ubfe.i64(i64 %src, i32 0, i32 %width)
   ret i64 %bfe
@@ -1066,12 +1053,9 @@
 declare i64 @llvm.amdgcn.sbfe.i64(i64, i32, i32) nounwind readnone
 
 ; CHECK-LABEL: @sbfe_offset_31(
-; CHECK-NEXT: %1 = sub i32 32, %width
-; CHECK-NEXT: %2 = shl i32 %src, %1
-; CHECK-NEXT: %bfe = ashr i32 %2, %1
-; CHECK-NEXT: ret i32 %bfe
+; CHECK-NEXT: %bfe = call i32 @llvm.amdgcn.sbfe.i32(i32 %src, i32 31, i32 %width)
 define i32 @sbfe_offset_31(i32 %src, i32 %width) {
-  %bfe = call i32 @llvm.amdgcn.sbfe.i32(i32 %src, i32 32, i32 %width)
+  %bfe = call i32 @llvm.amdgcn.sbfe.i32(i32 %src, i32 31, i32 %width)
   ret i32 %bfe
 }