[llvm-commits] [llvm] r169182 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombine.h lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp test/Transforms/InstCombine/2010-11-01-lshr-mask.ll test/Transforms/InstCombine/shift.ll test/Transforms/InstCombine/signext.ll

[Pete Couperus]

Hi Shuxin,

+    if (ShrAmt < ShlAmt) {
+      Constant *Amt = ConstantInt::get(VarX->getType(), ShlAmt - ShrAmt);
+      New = BinaryOperator::CreateShl(VarX, Amt);
+      BinaryOperator *Orig = cast<BinaryOperator>(Shl);
+      New->setHasNoSignedWrap(Orig->hasNoSignedWrap());
+      New->setHasNoUnsignedWrap(Orig->hasNoUnsignedWrap());
+    } else {
+      Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt);
+      New = BinaryOperator::CreateLShr(VarX, Amt);
+    }

Maybe I'm missing something, but shouldn't the
BinaryOperator::CreateLShr be Create[AL]Shr depending on the type you
started with, not unconditionally CreateLShr?

+define i32 @test60(i32 %x) {
+  %shr = ashr i32 %x, 4
+  %shl = shl i32 %shr, 1
+  %or = or i32 %shl, 1
+  ret i32 %or
+; CHECK: @test60
+; CHECK: lshr i32 %x, 3
+}

I would expect this to be ashr i32 %x, 3?

Pete