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Teach InstructionSimplify the trick of skipping incoming phi

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values that are equal to the phi itself.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119161 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2010-11-15 17:52:45 +00:00
parent 503dcc9822
commit 5520089465
2 changed files with 28 additions and 4 deletions
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13
lib/Analysis/InstructionSimplify.cpp
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@ -142,9 +142,12 @@ static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS,
// Evaluate the BinOp on the incoming phi values.
Value *CommonValue = 0;
for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
Value *Incoming = PI->getIncomingValue(i);
// If the incoming value is the phi node itself, it can be safely skipped.
if (Incoming == PI) continue;
Value *V = PI == LHS ?
SimplifyBinOp(Opcode, PI->getIncomingValue(i), RHS, TD, MaxRecurse) :
SimplifyBinOp(Opcode, LHS, PI->getIncomingValue(i), TD, MaxRecurse);
SimplifyBinOp(Opcode, Incoming, RHS, TD, MaxRecurse) :
SimplifyBinOp(Opcode, LHS, Incoming, TD, MaxRecurse);
// If the operation failed to simplify, or simplified to a different value
// to previously, then give up.
if (!V || (CommonValue && V != CommonValue))
@ -172,8 +175,10 @@ static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS,
// Evaluate the BinOp on the incoming phi values.
Value *CommonValue = 0;
for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
Value *V = SimplifyCmpInst(Pred, PI->getIncomingValue(i), RHS, TD,
MaxRecurse);
Value *Incoming = PI->getIncomingValue(i);
// If the incoming value is the phi node itself, it can be safely skipped.
if (Incoming == PI) continue;
Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, MaxRecurse);
// If the operation failed to simplify, or simplified to a different value
// to previously, then give up.
if (!V || (CommonValue && V != CommonValue))

19
test/Transforms/InstCombine/phi.ll
View File

@ -469,3 +469,22 @@ ret:
; CHECK: @test20
; CHECK: ret i1 false
}
define i1 @test21(i1 %c1, i1 %c2) {
%a = alloca i32
%b = alloca i32
%c = alloca i32
br i1 %c1, label %true, label %false
true:
br label %loop
false:
br label %loop
loop:
%p = phi i32* [ %a, %true ], [ %b, %false ], [ %p, %loop ]
%r = icmp eq i32* %p, %c
br i1 %c2, label %ret, label %loop
ret:
ret i1 %r
; CHECK: @test21
; CHECK: ret i1 false
}