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canonicalize:

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-%a + 42
into
42 - %a

previously we were emitting:
-(%a + 42)

This fixes the infinite loop in PR12338. The generated code is still not perfect, though.
Will work on that next

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158237 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nuno Lopes 2012-06-08 22:30:05 +00:00
parent 791e2e0867
commit 0f68fbb9e5
2 changed files with 29 additions and 4 deletions
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9
lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -170,10 +170,11 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
// -A + B --> B - A // -A + B --> B - A
// -A + -B --> -(A + B) // -A + -B --> -(A + B)
if (Value *LHSV = dyn_castNegVal(LHS)) { if (Value *LHSV = dyn_castNegVal(LHS)) {
if (Value *RHSV = dyn_castNegVal(RHS)) { if (!isa<Constant>(RHS))
Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum"); if (Value *RHSV = dyn_castNegVal(RHS)) {
return BinaryOperator::CreateNeg(NewAdd); Value *NewAdd = Builder->CreateAdd(LHSV, RHSV, "sum");
} return BinaryOperator::CreateNeg(NewAdd);
}
return BinaryOperator::CreateSub(RHS, LHSV); return BinaryOperator::CreateSub(RHS, LHSV);
} }

24
test/Transforms/InstCombine/pr12338.ll Normal file
View File

@ -0,0 +1,24 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
define void @entry() nounwind {
entry:
br label %for.cond
for.cond:
%local = phi <1 x i32> [ <i32 0>, %entry ], [ %phi2, %cond.end47 ]
; CHECK: sub <1 x i32> <i32 92>, %local
%phi3 = sub <1 x i32> zeroinitializer, %local
br label %cond.end
cond.false:
br label %cond.end
cond.end:
%cond = phi <1 x i32> [ %phi3, %for.cond ], [ undef, %cond.false ]
br label %cond.end47
cond.end47:
%sum = add <1 x i32> %cond, <i32 92>
%phi2 = sub <1 x i32> zeroinitializer, %sum
br label %for.cond
}