Fix for two constant propagation problems in GVN with the assume intrinsic
instruction.
Patch by Yuanrui Zhang.
Differential Revision: http://reviews.llvm.org/D16100
llvm-svn: 258435
diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index 3ae01657..6c217c9 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -316,7 +316,7 @@
unsigned replaceDominatedUsesWith(Value *From, Value *To, DominatorTree &DT,
const BasicBlockEdge &Edge);
/// \brief Replace each use of 'From' with 'To' if that use is dominated by
-/// the given BasicBlock. Returns the number of replacements made.
+/// the end of the given BasicBlock. Returns the number of replacements made.
unsigned replaceDominatedUsesWith(Value *From, Value *To, DominatorTree &DT,
const BasicBlock *BB);
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index a028b8c4..5f55db6 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -2133,7 +2133,8 @@
/// The given values are known to be equal in every block
/// dominated by 'Root'. Exploit this, for example by replacing 'LHS' with
/// 'RHS' everywhere in the scope. Returns whether a change was made.
-/// If DominatesByEdge is false, then it means that it is dominated by Root.End.
+/// If DominatesByEdge is false, then it means that we will propagate the RHS
+/// value starting from the end of Root.Start.
bool GVN::propagateEquality(Value *LHS, Value *RHS, const BasicBlockEdge &Root,
bool DominatesByEdge) {
SmallVector<std::pair<Value*, Value*>, 4> Worklist;
@@ -2195,7 +2196,7 @@
unsigned NumReplacements =
DominatesByEdge
? replaceDominatedUsesWith(LHS, RHS, *DT, Root)
- : replaceDominatedUsesWith(LHS, RHS, *DT, Root.getEnd());
+ : replaceDominatedUsesWith(LHS, RHS, *DT, Root.getStart());
Changed |= NumReplacements > 0;
NumGVNEqProp += NumReplacements;
@@ -2271,7 +2272,7 @@
DominatesByEdge
? replaceDominatedUsesWith(NotCmp, NotVal, *DT, Root)
: replaceDominatedUsesWith(NotCmp, NotVal, *DT,
- Root.getEnd());
+ Root.getStart());
Changed |= NumReplacements > 0;
NumGVNEqProp += NumReplacements;
}
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 3e69553..ed941a7 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1569,7 +1569,7 @@
UI != UE;) {
Use &U = *UI++;
auto *I = cast<Instruction>(U.getUser());
- if (DT.dominates(BB, I->getParent())) {
+ if (DT.properlyDominates(BB, I->getParent())) {
U.set(To);
DEBUG(dbgs() << "Replace dominated use of '" << From->getName() << "' as "
<< *To << " in " << *U << "\n");
diff --git a/llvm/test/Transforms/GVN/assume-equal.ll b/llvm/test/Transforms/GVN/assume-equal.ll
index f9304a8..d423c16 100644
--- a/llvm/test/Transforms/GVN/assume-equal.ll
+++ b/llvm/test/Transforms/GVN/assume-equal.ll
@@ -226,6 +226,46 @@
ret i32 17
}
+; This test checks if GVN can do the constant propagation correctly
+; when there are multiple uses of the same assume value in the
+; basic block that has a loop back-edge pointing to itself.
+;
+; CHECK-LABEL: define i32 @_Z1il(i32 %val, i1 %k)
+define i32 @_Z1il(i32 %val, i1 %k) {
+ br label %next
+
+next:
+; CHECK: tail call void @llvm.assume(i1 %k)
+; CHECK-NEXT: %cmp = icmp eq i32 %val, 50
+ tail call void @llvm.assume(i1 %k)
+ tail call void @llvm.assume(i1 %k)
+ %cmp = icmp eq i32 %val, 50
+ br i1 %cmp, label %next, label %meh
+
+meh:
+ ret i32 0
+}
+
+; This test checks if GVN can prevent the constant propagation correctly
+; in the successor blocks that are not dominated by the basic block
+; with the assume instruction.
+;
+; CHECK-LABEL: define i1 @_z1im(i32 %val, i1 %k, i1 %j)
+define i1 @_z1im(i32 %val, i1 %k, i1 %j) {
+ br i1 %j, label %next, label %meh
+
+next:
+; CHECK: tail call void @llvm.assume(i1 %k)
+; CHECK-NEXT: br label %meh
+ tail call void @llvm.assume(i1 %k)
+ tail call void @llvm.assume(i1 %k)
+ br label %meh
+
+meh:
+; CHECK: ret i1 %k
+ ret i1 %k
+}
+
declare noalias i8* @_Znwm(i64)
declare void @_ZN1AC1Ev(%struct.A*)
declare void @llvm.assume(i1)