Revert "InstCombine: merge constants in both operands of icmp."

This reverts commit r204912, and follow-up commit r204948.

This introduced a performance regression, and the fix is not completely
clear yet.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205010 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/README.txt

@@ -930,6 +930,18 @@ optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
 
 //===---------------------------------------------------------------------===//
 
+int g(int x) { return (x - 10) < 0; }
+Should combine to "x <= 9" (the sub has nsw).  Currently not
+optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
+
+//===---------------------------------------------------------------------===//
+
+int g(int x) { return (x + 10) < 0; }
+Should combine to "x < -10" (the add has nsw).  Currently not
+optimized with "clang -emit-llvm-bc | opt -std-compile-opts".
+
+//===---------------------------------------------------------------------===//
+
 int f(int i, int j) { return i < j + 1; }
 int g(int i, int j) { return j > i - 1; }
 Should combine to "i <= j" (the add/sub has nsw).  Currently not

lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -3008,20 +3008,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
     // icmp X, X+Cst
     if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
       return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate());
-
-    ConstantInt *Cst2;
-    if (I.isSigned() &&
-        match(Op1, m_ConstantInt(Cst)) &&
-        match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst2))) &&
-        cast<BinaryOperator>(Op0)->hasNoSignedWrap()) {
-      // icmp X+Cst2, Cst --> icmp X, Cst-Cst2
-      // iff Cst-Cst2 does not overflow
-      bool Overflow;
-      APInt NewCst = Cst->getValue().ssub_ov(Cst2->getValue(), Overflow);
-      if (!Overflow)
-        return new ICmpInst(I.getPredicate(), X,
-                            ConstantInt::get(Cst->getType(), NewCst));
-    }
   }
   return Changed ? &I : 0;
 }

test/Transforms/InstCombine/icmp.ll

@@ -1356,66 +1356,3 @@ define i1 @icmp_ashr_ashr_ne(i32 %a, i32 %b) nounwind {
  %z = icmp ne i32 %x, %y
  ret i1 %z
 }
-
-; CHECK-LABEL: icmp_add_const_const1
-; CHECK: %cmp = icmp slt i32 %x, -10
-; CHECK-NOT: %add = add nsw i32 %x, 10
-define i32 @icmp_add_const_const1(i32 %x) nounwind ssp uwtable {
-entry:
-  %add = add nsw i32 %x, 10
-  %cmp = icmp slt i32 %add, 0
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
-}
-
-; CHECK-LABEL: icmp_add_const_const2
-; CHECK: %cmp = icmp slt i32 %x, -10
-; CHECK-NOT: %add = add nsw i32 %x, 10
-define i32 @icmp_add_const_const2(i32 %x) nounwind ssp uwtable {
-entry:
-  %add = add nsw i32 10, %x
-  %cmp = icmp sgt i32 0, %add
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
-}
-
-; CHECK-LABEL: icmp_add_const_const3
-; CHECK: %cmp = icmp slt i32 %x, 20
-; CHECK-NOT: %sub = add nsw i32 %x, -10
-define i32 @icmp_add_const_const3(i32 %x) nounwind ssp uwtable {
-entry:
-  %add = add nsw i32 -10, %x
-  %cmp = icmp sgt i32 10, %add
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
-}
-
-; CHECK-LABEL: icmp_add_const_intmin
-; CHECK: %cmp = icmp ne i32 %x, 2147483638
-define i32 @icmp_add_const_intmin(i32 %x) nounwind ssp uwtable {
-entry:
-  %add = add nsw i32 %x, 10
-  %cmp = icmp sgt i32 %add, -2147483648
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
-}
-
-; CHECK-LABEL: icmp_add_const_intmax
-; CHECK: %cmp = icmp ne i32 %x, 2147483637
-define i32 @icmp_add_const_intmax(i32 %x) nounwind ssp uwtable {
-entry:
-  %add = add nsw i32 %x, 10
-  %cmp = icmp slt i32 %add, 2147483647
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
-}
-
-; CHECK-LABEL: icmp_add_const_ult
-; CHECK: %cmp = icmp ult i32 %add, 6
-define i32 @icmp_add_const_ult(i32 %a) #0 {
-entry:
-  %add = add nsw i32 %a, -49
-  %cmp = icmp ult i32 %add, 6
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
-}