Merging r348181:

------------------------------------------------------------------------
r348181 | lebedevri | 2018-12-03 12:07:58 -0800 (Mon, 03 Dec 2018) | 8 lines

[InstCombine] foldICmpWithLowBitMaskedVal(): disable 2 faulty folds.

These two folds are invalid for this non-constant pattern
when the mask ends up being all-ones:
https://rise4fun.com/Alive/9au
https://rise4fun.com/Alive/UcQM

Fixes https://bugs.llvm.org/show_bug.cgi?id=39861
------------------------------------------------------------------------

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@348528 91177308-0d34-0410-b5e6-96231b3b80d8

Author: tstellar

lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -2924,12 +2924,16 @@ static Value *foldICmpWithLowBitMaskedVal(ICmpInst &I,
     //  x & (-1 >> y) s>= x    ->    x s<= (-1 >> y)
     if (X != I.getOperand(1)) // X must be on RHS of comparison!
       return nullptr;         // Ignore the other case.
+    if (!match(M, m_Constant())) // Can not do this fold with non-constant.
+      return nullptr;
     DstPred = ICmpInst::Predicate::ICMP_SLE;
     break;
   case ICmpInst::Predicate::ICMP_SLT:
     //  x & (-1 >> y) s< x    ->    x s> (-1 >> y)
     if (X != I.getOperand(1)) // X must be on RHS of comparison!
       return nullptr;         // Ignore the other case.
+    if (!match(M, m_Constant())) // Can not do this fold with non-constant.
+      return nullptr;
     DstPred = ICmpInst::Predicate::ICMP_SGT;
     break;
   case ICmpInst::Predicate::ICMP_SLE:

test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sge-to-icmp-sle.ll

@@ -26,8 +26,9 @@ define i1 @p0(i8 %x) {
 define i1 @pv(i8 %x, i8 %y) {
 ; CHECK-LABEL: @pv(
 ; CHECK-NEXT:    [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sge i8 [[TMP0]], [[X:%.*]]
-; CHECK-NEXT:    ret i1 [[TMP1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[TMP0]], [[X:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = icmp sge i8 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i1 [[RET]]
 ;
   %tmp0 = lshr i8 -1, %y
   %tmp1 = and i8 %tmp0, %x
@@ -120,8 +121,9 @@ define i1 @cv0(i8 %y) {
 ; CHECK-LABEL: @cv0(
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
 ; CHECK-NEXT:    [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sle i8 [[X]], [[TMP0]]
-; CHECK-NEXT:    ret i1 [[TMP1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[X]], [[TMP0]]
+; CHECK-NEXT:    [[RET:%.*]] = icmp sge i8 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i1 [[RET]]
 ;
   %x = call i8 @gen8()
   %tmp0 = lshr i8 -1, %y

test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-slt-to-icmp-sgt.ll

@@ -26,8 +26,9 @@ define i1 @p0(i8 %x) {
 define i1 @pv(i8 %x, i8 %y) {
 ; CHECK-LABEL: @pv(
 ; CHECK-NEXT:    [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i8 [[TMP0]], [[X:%.*]]
-; CHECK-NEXT:    ret i1 [[TMP1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[TMP0]], [[X:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = icmp slt i8 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i1 [[RET]]
 ;
   %tmp0 = lshr i8 -1, %y
   %tmp1 = and i8 %tmp0, %x
@@ -120,8 +121,9 @@ define i1 @cv0(i8 %y) {
 ; CHECK-LABEL: @cv0(
 ; CHECK-NEXT:    [[X:%.*]] = call i8 @gen8()
 ; CHECK-NEXT:    [[TMP0:%.*]] = lshr i8 -1, [[Y:%.*]]
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i8 [[X]], [[TMP0]]
-; CHECK-NEXT:    ret i1 [[TMP1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[X]], [[TMP0]]
+; CHECK-NEXT:    [[RET:%.*]] = icmp slt i8 [[TMP1]], [[X]]
+; CHECK-NEXT:    ret i1 [[RET]]
 ;
   %x = call i8 @gen8()
   %tmp0 = lshr i8 -1, %y