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

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

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

llvm-svn: 205010
This commit is contained in:
Erik Verbruggen 2014-03-28 14:50:57 +00:00
parent 06cf5cbf74
commit 11e61b79e5
3 changed files with 12 additions and 77 deletions
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12
lib/Target/README.txt
View File

@ -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

14
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -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;
}

63
test/Transforms/InstCombine/icmp.ll
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@ -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
}