[llvm-branch-commits] [llvm-branch] r123011 - in /llvm/branches/Apple/whitney: lib/Transforms/InstCombine/InstCombineShifts.cpp test/Transforms/InstCombine/shift.ll

[Daniel Dunbar]

Author: ddunbar
Date: Fri Jan  7 13:32:38 2011
New Revision: 123011

URL: http://llvm.org/viewvc/llvm-project?rev=123011&view=rev
Log:
Merge r122529:
--
Author: Owen Anderson <owen at apple.com>
Date:   Thu Dec 23 23:56:24 2010 +0000

    When determining if we can fold (x >> C1) << C2, the bits that we need to verify are zero
    are not the low bits of x, but the bits that WILL be the low bits after the operation completes.

Modified:
    llvm/branches/Apple/whitney/lib/Transforms/InstCombine/InstCombineShifts.cpp
    llvm/branches/Apple/whitney/test/Transforms/InstCombine/shift.ll

Modified: llvm/branches/Apple/whitney/lib/Transforms/InstCombine/InstCombineShifts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/Apple/whitney/lib/Transforms/InstCombine/InstCombineShifts.cpp?rev=123011&r1=123010&r2=123011&view=diff
==============================================================================
--- llvm/branches/Apple/whitney/lib/Transforms/InstCombine/InstCombineShifts.cpp (original)
+++ llvm/branches/Apple/whitney/lib/Transforms/InstCombine/InstCombineShifts.cpp Fri Jan  7 13:32:38 2011
@@ -155,8 +155,9 @@
     // We can always turn lshr(c1)+shl(c2) -> lshr(c3)+and(c4), but it isn't
     // profitable unless we know the and'd out bits are already zero.
     if (CI->getZExtValue() > NumBits) {
+      unsigned LowBits = CI->getZExtValue() - NumBits;
       if (MaskedValueIsZero(I->getOperand(0),
-                            APInt::getLowBitsSet(TypeWidth, NumBits)))
+                          APInt::getLowBitsSet(TypeWidth, NumBits) << LowBits))
         return true;
     }
       

Modified: llvm/branches/Apple/whitney/test/Transforms/InstCombine/shift.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/Apple/whitney/test/Transforms/InstCombine/shift.ll?rev=123011&r1=123010&r2=123011&view=diff
==============================================================================
--- llvm/branches/Apple/whitney/test/Transforms/InstCombine/shift.ll (original)
+++ llvm/branches/Apple/whitney/test/Transforms/InstCombine/shift.ll Fri Jan  7 13:32:38 2011
@@ -441,3 +441,22 @@
 ; CHECK:  %ins = or i128 %tmp23, %A
 ; CHECK:  %tmp46 = trunc i128 %ins to i64
 }
+; <rdar://problem/8756731>
+; CHECK: @test39
+define i8 @test39(i32 %a0) {
+entry:
+  %tmp4 = trunc i32 %a0 to i8
+; CHECK: and i8 %tmp49, 64
+  %tmp5 = shl i8 %tmp4, 5
+  %tmp48 = and i8 %tmp5, 32
+  %tmp49 = lshr i8 %tmp48, 5
+  %tmp50 = mul i8 %tmp49, 64
+  %tmp51 = xor i8 %tmp50, %tmp5
+; CHECK: and i8 %0, 16
+  %tmp52 = and i8 %tmp51, -128
+  %tmp53 = lshr i8 %tmp52, 7
+  %tmp54 = mul i8 %tmp53, 16
+  %tmp55 = xor i8 %tmp54, %tmp51
+; CHECK: ret i8 %tmp551
+  ret i8 %tmp55
+}