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| author | Max Kazantsev <mkazantsev@azul.com> | 2021-10-09 14:47:44 +0700 |
|---|---|---|
| committer | Max Kazantsev <mkazantsev@azul.com> | 2021-10-09 14:47:44 +0700 |
| commit | 4c0da2366305c49672d89ee0e90afcf85fa2641f (patch) | |
| tree | 6a09cd174a8063283b418287d853b4bb133a68de | |
| parent | 49ca01047f0c1d0003ee49ebec5a6fa154aa6612 (diff) | |
| download | llvm-4c0da2366305c49672d89ee0e90afcf85fa2641f.zip llvm-4c0da2366305c49672d89ee0e90afcf85fa2641f.tar.gz llvm-4c0da2366305c49672d89ee0e90afcf85fa2641f.tar.bz2 | |
[LoopDeletion] Support selects when symbolically evaluating 1st iteration
Adds support for selects for which we know value on the 1st iteration.
Differential Revision: https://reviews.llvm.org/D104111
Reviewed By: nikic
| -rw-r--r-- | llvm/lib/Transforms/Scalar/LoopDeletion.cpp | 8 | ||||
| -rw-r--r-- | llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll | 9 |
2 files changed, 12 insertions, 5 deletions
diff --git a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp index e1e5ef9..03f7f25 100644 --- a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp +++ b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp @@ -197,6 +197,14 @@ getValueOnFirstIteration(Value *V, DenseMap<Value *, Value *> &FirstIterValue, Value *RHS = getValueOnFirstIteration(Cmp->getOperand(1), FirstIterValue, SQ); FirstIterV = SimplifyICmpInst(Cmp->getPredicate(), LHS, RHS, SQ); + } else if (auto *Select = dyn_cast<SelectInst>(V)) { + Value *Cond = + getValueOnFirstIteration(Select->getCondition(), FirstIterValue, SQ); + if (auto *C = dyn_cast<ConstantInt>(Cond)) { + auto *Selected = C->isAllOnesValue() ? Select->getTrueValue() + : Select->getFalseValue(); + FirstIterV = getValueOnFirstIteration(Selected, FirstIterValue, SQ); + } } if (!FirstIterV) FirstIterV = V; diff --git a/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll b/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll index 18f4805..1bdcefc 100644 --- a/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll +++ b/llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll @@ -979,25 +979,24 @@ failure: unreachable } -; TODO: We can break the backedge here. define i32 @test_select_const(i32 %x) { ; CHECK-LABEL: @test_select_const( ; CHECK-NEXT: entry: ; CHECK-NEXT: br label [[LOOP:%.*]] ; CHECK: loop: -; CHECK-NEXT: [[SUM:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[SUM_NEXT:%.*]], [[BACKEDGE:%.*]] ] +; CHECK-NEXT: [[SUM:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ] ; CHECK-NEXT: [[SUB:%.*]] = sub i32 4, [[SUM]] ; CHECK-NEXT: [[IS_POSITIVE:%.*]] = icmp sgt i32 [[SUB]], 0 ; CHECK-NEXT: [[SEL:%.*]] = select i1 [[IS_POSITIVE]], i32 [[SUB]], i32 [[X:%.*]] ; CHECK-NEXT: [[SEL_COND:%.*]] = icmp sgt i32 [[SEL]], 0 -; CHECK-NEXT: br i1 [[SEL_COND]], label [[BACKEDGE]], label [[IF_FALSE:%.*]] +; CHECK-NEXT: br i1 [[SEL_COND]], label [[BACKEDGE:%.*]], label [[IF_FALSE:%.*]] ; CHECK: if.false: ; CHECK-NEXT: br label [[BACKEDGE]] ; CHECK: backedge: ; CHECK-NEXT: [[MERGE_PHI:%.*]] = phi i32 [ 0, [[IF_FALSE]] ], [ [[SUB]], [[LOOP]] ] -; CHECK-NEXT: [[SUM_NEXT]] = add i32 [[SUM]], [[MERGE_PHI]] +; CHECK-NEXT: [[SUM_NEXT:%.*]] = add i32 [[SUM]], [[MERGE_PHI]] ; CHECK-NEXT: [[LOOP_COND:%.*]] = icmp ne i32 [[SUM_NEXT]], 4 -; CHECK-NEXT: br i1 [[LOOP_COND]], label [[LOOP]], label [[DONE:%.*]] +; CHECK-NEXT: br label [[DONE:%.*]] ; CHECK: done: ; CHECK-NEXT: [[SUM_NEXT_LCSSA:%.*]] = phi i32 [ [[SUM_NEXT]], [[BACKEDGE]] ] ; CHECK-NEXT: ret i32 [[SUM_NEXT_LCSSA]] |