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| author | Sanjoy Das <sanjoy@playingwithpointers.com> | 2015-11-06 19:01:03 +0000 |
|---|---|---|
| committer | Sanjoy Das <sanjoy@playingwithpointers.com> | 2015-11-06 19:01:03 +0000 |
| commit | c01b4d2b28184d0a9efee934c8a5b7aab57984ab (patch) | |
| tree | fdd6313ad25e0502f572b34f09b6b674bfa5b44f | |
| parent | 9349dcc74a10f3056639b455d56288e62e23f13c (diff) | |
| download | bcm5719-llvm-c01b4d2b28184d0a9efee934c8a5b7aab57984ab.tar.gz bcm5719-llvm-c01b4d2b28184d0a9efee934c8a5b7aab57984ab.zip | |
[ValueTracking] De-pessimize isImpliedCondition around unsigned compares
Summary:
Currently `isImpliedCondition` will optimize "I +_nuw C < L ==> I < L"
only if C is positive. This is an unnecessary restriction -- the
implication holds even if `C` is negative.
Reviewers: reames, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D14369
llvm-svn: 252332
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 8 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstSimplify/implies.ll | 13 |
2 files changed, 16 insertions, 5 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 3dc9f3a1037..f4824aebe52 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -4109,12 +4109,12 @@ static bool isTruePredicate(CmpInst::Predicate Pred, Value *LHS, Value *RHS) { case CmpInst::ICMP_ULE: { ConstantInt *CI; - // LHS u< LHS +_{nuw} C if C > 0 - // LHS u<= LHS +_{nuw} C if C >= 0 + // LHS u< LHS +_{nuw} C if C != 0 + // LHS u<= LHS +_{nuw} C if (match(RHS, m_NUWAdd(m_Specific(LHS), m_ConstantInt(CI)))) { if (Pred == CmpInst::ICMP_ULT) - return CI->getValue().isStrictlyPositive(); - return !CI->isNegative(); + return !CI->isZero(); + return true; } return false; } diff --git a/llvm/test/Transforms/InstSimplify/implies.ll b/llvm/test/Transforms/InstSimplify/implies.ll index 8e5bbf2c897..eb8db4224fa 100644 --- a/llvm/test/Transforms/InstSimplify/implies.ll +++ b/llvm/test/Transforms/InstSimplify/implies.ll @@ -65,7 +65,7 @@ define i1 @test3(i32 %length.i, i32 %i) { ret i1 %res } -; i +_{nuw} C_{>0} <u L ==> i <u L +; i +_{nuw} C <u L ==> i <u L define i1 @test4(i32 %length.i, i32 %i) { ; CHECK-LABEL: @test4 ; CHECK: ret i1 true @@ -116,6 +116,17 @@ define i1 @test8(i32 %length.i, i32 %i) { ret i1 %res } +; i +_{nuw} C <s L ==> i < L, even if C is negative +define i1 @test9(i32 %length.i, i32 %i) { +; CHECK-LABEL: @test9( +; CHECK: ret i1 true + %iplus1 = add nuw i32 %i, -100 + %var29 = icmp ult i32 %i, %length.i + %var30 = icmp ult i32 %iplus1, %length.i + %res = icmp ule i1 %var30, %var29 + ret i1 %res +} + ; X >=(s) Y == X ==> Y (i1 1 becomes -1 for reasoning) define i1 @test_sge(i32 %length.i, i32 %i) { ; CHECK-LABEL: @test_sge |
