[llvm] 703f6a6 - [ConstraintElimination] Support conditions from loop preheaders
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 4 05:58:52 PST 2021
Author: Florian Hahn
Date: 2021-02-04T13:58:32Z
New Revision: 703f6a6828b51cd2b475982a9de2af242dfba97c
URL: https://github.com/llvm/llvm-project/commit/703f6a6828b51cd2b475982a9de2af242dfba97c
DIFF: https://github.com/llvm/llvm-project/commit/703f6a6828b51cd2b475982a9de2af242dfba97c.diff
LOG: [ConstraintElimination] Support conditions from loop preheaders
This patch extends the condition collection logic to allow adding
conditions from pre-headers to loop headers, by allowing cases where the
target block dominates some of its predecessors.
Added:
Modified:
llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
llvm/test/Transforms/ConstraintElimination/dom.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index a127f0b391d7..f6a6b4807adf 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -247,6 +247,15 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
if (!Br || !Br->isConditional())
continue;
+ // Returns true if we can add a known condition from BB to its successor
+ // block Succ. Each predecessor of Succ can either be BB or be dominated by
+ // Succ (e.g. the case when adding a condition from a pre-header to a loop
+ // header).
+ auto CanAdd = [&BB, &DT](BasicBlock *Succ) {
+ return all_of(predecessors(Succ), [&BB, &DT, Succ](BasicBlock *Pred) {
+ return Pred == &BB || DT.dominates(Succ, Pred);
+ });
+ };
// If the condition is an OR of 2 compares and the false successor only has
// the current block as predecessor, queue both negated conditions for the
// false successor.
@@ -254,7 +263,7 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
if (match(Br->getCondition(), m_LogicalOr(m_Value(Op0), m_Value(Op1))) &&
match(Op0, m_Cmp()) && match(Op1, m_Cmp())) {
BasicBlock *FalseSuccessor = Br->getSuccessor(1);
- if (FalseSuccessor->getSinglePredecessor()) {
+ if (CanAdd(FalseSuccessor)) {
WorkList.emplace_back(DT.getNode(FalseSuccessor), cast<CmpInst>(Op0),
true);
WorkList.emplace_back(DT.getNode(FalseSuccessor), cast<CmpInst>(Op1),
@@ -269,7 +278,7 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
if (match(Br->getCondition(), m_LogicalAnd(m_Value(Op0), m_Value(Op1))) &&
match(Op0, m_Cmp()) && match(Op1, m_Cmp())) {
BasicBlock *TrueSuccessor = Br->getSuccessor(0);
- if (TrueSuccessor->getSinglePredecessor()) {
+ if (CanAdd(TrueSuccessor)) {
WorkList.emplace_back(DT.getNode(TrueSuccessor), cast<CmpInst>(Op0),
false);
WorkList.emplace_back(DT.getNode(TrueSuccessor), cast<CmpInst>(Op1),
@@ -281,9 +290,9 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
auto *CmpI = dyn_cast<CmpInst>(Br->getCondition());
if (!CmpI)
continue;
- if (Br->getSuccessor(0)->getSinglePredecessor())
+ if (CanAdd(Br->getSuccessor(0)))
WorkList.emplace_back(DT.getNode(Br->getSuccessor(0)), CmpI, false);
- if (Br->getSuccessor(1)->getSinglePredecessor())
+ if (CanAdd(Br->getSuccessor(1)))
WorkList.emplace_back(DT.getNode(Br->getSuccessor(1)), CmpI, true);
}
diff --git a/llvm/test/Transforms/ConstraintElimination/dom.ll b/llvm/test/Transforms/ConstraintElimination/dom.ll
index 424e98742289..1c3e120a8962 100644
--- a/llvm/test/Transforms/ConstraintElimination/dom.ll
+++ b/llvm/test/Transforms/ConstraintElimination/dom.ll
@@ -146,9 +146,9 @@ define void @test_cond_from_preheader(i32 %x, i1 %c) {
; CHECK-NEXT: br i1 [[C_1]], label [[LOOP:%.*]], label [[BB2]]
; CHECK: loop:
; CHECK-NEXT: [[T_1:%.*]] = icmp ule i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[T_1]])
+; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[F_1:%.*]] = icmp ugt i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[F_1]])
+; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[C_2:%.*]] = icmp ule i32 [[X]], 9
; CHECK-NEXT: call void @use(i1 [[C_2]])
; CHECK-NEXT: [[C_3:%.*]] = icmp ugt i32 [[X]], 9
@@ -156,7 +156,7 @@ define void @test_cond_from_preheader(i32 %x, i1 %c) {
; CHECK-NEXT: br i1 true, label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: [[C_4:%.*]] = icmp ule i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[C_4]])
+; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: ret void
; CHECK: bb2:
; CHECK-NEXT: [[C_5:%.*]] = icmp ugt i32 [[X]], 10
@@ -203,9 +203,9 @@ define void @test_cond_from_preheader_successors_flipped(i32 %x, i1 %c) {
; CHECK-NEXT: br i1 [[C_1]], label [[BB2]], label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[F_1:%.*]] = icmp ule i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[F_1]])
+; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[T_1:%.*]] = icmp ugt i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[T_1]])
+; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[C_2:%.*]] = icmp ule i32 [[X]], 11
; CHECK-NEXT: call void @use(i1 [[C_2]])
; CHECK-NEXT: [[C_3:%.*]] = icmp ugt i32 [[X]], 11
@@ -213,7 +213,7 @@ define void @test_cond_from_preheader_successors_flipped(i32 %x, i1 %c) {
; CHECK-NEXT: br i1 true, label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: [[F_2:%.*]] = icmp ule i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[F_2]])
+; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: ret void
; CHECK: bb2:
; CHECK-NEXT: [[C_5:%.*]] = icmp ugt i32 [[X]], 10
@@ -266,17 +266,17 @@ define void @test_cond_from_preheader_and(i32 %x, i32 %y, i1 %c) {
; CHECK-NEXT: br i1 [[AND]], label [[LOOP:%.*]], label [[EXIT_1:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[T_1:%.*]] = icmp ule i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[T_1]])
+; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[F_1:%.*]] = icmp ugt i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[F_1]])
+; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[C_1:%.*]] = icmp ule i32 [[X]], 9
; CHECK-NEXT: call void @use(i1 [[C_1]])
; CHECK-NEXT: [[C_2:%.*]] = icmp ugt i32 [[X]], 9
; CHECK-NEXT: call void @use(i1 [[C_2]])
; CHECK-NEXT: [[T_2:%.*]] = icmp ugt i32 [[Y]], 99
-; CHECK-NEXT: call void @use(i1 [[T_2]])
+; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[F_2:%.*]] = icmp ule i32 [[Y]], 99
-; CHECK-NEXT: call void @use(i1 [[F_2]])
+; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[C_3:%.*]] = icmp ugt i32 [[Y]], 100
; CHECK-NEXT: call void @use(i1 [[C_3]])
; CHECK-NEXT: [[C_4:%.*]] = icmp ugt i32 [[Y]], 100
@@ -425,17 +425,17 @@ define void @test_cond_from_preheader_or(i32 %x, i32 %y, i1 %c) {
; CHECK-NEXT: br i1 [[OR]], label [[EXIT_1:%.*]], label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[T_1:%.*]] = icmp ugt i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[T_1]])
+; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[F_1:%.*]] = icmp ule i32 [[X]], 10
-; CHECK-NEXT: call void @use(i1 [[F_1]])
+; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[C_1:%.*]] = icmp ugt i32 [[X]], 11
; CHECK-NEXT: call void @use(i1 [[C_1]])
; CHECK-NEXT: [[C_2:%.*]] = icmp ule i32 [[X]], 11
; CHECK-NEXT: call void @use(i1 [[C_2]])
; CHECK-NEXT: [[T_2:%.*]] = icmp ule i32 [[Y]], 99
-; CHECK-NEXT: call void @use(i1 [[T_2]])
+; CHECK-NEXT: call void @use(i1 true)
; CHECK-NEXT: [[F_2:%.*]] = icmp ugt i32 [[Y]], 99
-; CHECK-NEXT: call void @use(i1 [[F_2]])
+; CHECK-NEXT: call void @use(i1 false)
; CHECK-NEXT: [[C_3:%.*]] = icmp ule i32 [[Y]], 98
; CHECK-NEXT: call void @use(i1 [[C_3]])
; CHECK-NEXT: [[C_4:%.*]] = icmp ule i32 [[Y]], 98
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