Author: Anton Rapetov
Date: 2021-01-21T12:33:06-08:00
New Revision: bfec9148a042c8fd6093ae0d54c784211a295c6c
URL: https://github.com/llvm/llvm-project/commit/bfec9148a042c8fd6093ae0d54c784211a295c6c
DIFF: https://github.com/llvm/llvm-project/commit/bfec9148a042c8fd6093ae0d54c784211a295c6c.diff
LOG: Scalar: Don't visit constants in findInnerReductionPhi in LoopInterchange
In LoopInterchange, `findInnerReductionPhi()` looks for reduction
variables, which cannot be constants. Update it to return early in that
case.
This also addresses a blocker for removing use-lists from ConstantData,
whose users could be spread across arbitrary modules in the same
LLVMContext.
Differential Revision: https://reviews.llvm.org/D94712
Added:
Modified:
llvm/lib/Transforms/Scalar/LoopInterchange.cpp
llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
index a93273970a2f..d9dbc0deb42a 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -661,6 +661,10 @@ static Value *followLCSSA(Value *SV) {
// Check V's users to see if it is involved in a reduction in L.
static PHINode *findInnerReductionPhi(Loop *L, Value *V) {
+ // Reduction variables cannot be constants.
+ if (isa<Constant>(V))
+ return nullptr;
+
for (Value *User : V->users()) {
if (PHINode *PHI = dyn_cast<PHINode>(User)) {
if (PHI->getNumIncomingValues() == 1)
diff --git a/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll b/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
index 24c5184a4156..03bd5b71af94 100644
--- a/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
+++ b/llvm/test/Transforms/LoopInterchange/reductions-across-inner-and-outer-loop.ll
@@ -150,3 +150,42 @@ for1.loopexit: ; preds = %for1.inc
%sum.inc.lcssa2 = phi i64 [ %sum.inc.lcssa, %for1.inc ]
ret i64 %sum.inc.lcssa2
}
+
+; Check that we do not interchange or crash if the PHI in the outer loop gets a
+; constant from the inner loop.
+; REMARKS: --- !Missed
+; REMARKS-NEXT: Pass: loop-interchange
+; REMARKS-NEXT: Name: UnsupportedPHIOuter
+; REMARKS-NEXT: Function: test_constant_inner_loop_res
+
+define i64 @test_constant_inner_loop_res([100 x [100 x i64]]* %Arr) {
+entry:
+ br label %for1.header
+
+for1.header: ; preds = %for1.inc, %entry
+ %indvars.iv23 = phi i64 [ 0, %entry ], [ %indvars.iv.next24, %for1.inc ]
+ %sum.outer = phi i64 [ 0, %entry ], [ %sum.inc.amend, %for1.inc ]
+ br label %for2
+
+for2: ; preds = %for2, %for1.header
+ %indvars.iv = phi i64 [ 0, %for1.header ], [ %indvars.iv.next.3, %for2 ]
+ %sum.inner = phi i64 [ %sum.outer, %for1.header ], [ %sum.inc, %for2 ]
+ %arrayidx = getelementptr inbounds [100 x [100 x i64]], [100 x [100 x i64]]* %Arr, i64 0, i64 %indvars.iv, i64 %indvars.iv23
+ %lv = load i64, i64* %arrayidx, align 4
+ %sum.inc = add i64 %sum.inner, %lv
+ %indvars.iv.next.3 = add nuw nsw i64 %indvars.iv, 1
+ %exit1 = icmp eq i64 %indvars.iv.next.3, 100
+ br i1 %exit1, label %for1.inc, label %for2
+
+for1.inc: ; preds = %for2
+ %sum.inc.lcssa = phi i64 [ %sum.inc, %for2 ]
+ %const.lcssa = phi i64 [ 0, %for2 ]
+ %sum.inc.amend = add i64 %const.lcssa, %sum.inc.lcssa
+ %indvars.iv.next24 = add nuw nsw i64 %indvars.iv23, 1
+ %exit2 = icmp eq i64 %indvars.iv.next24, 100
+ br i1 %exit2, label %for1.loopexit, label %for1.header
+
+for1.loopexit: ; preds = %for1.inc
+ %il.res.lcssa2 = phi i64 [ %sum.inc.amend, %for1.inc ]
+ ret i64 %il.res.lcssa2
+}