[llvm] r331799 - [LV] Fix for PR37248, Broadcast codegen incorrectly assumed vector loop body is single basic block
Hideki Saito via llvm-commits
llvm-commits at lists.llvm.org
Tue May 8 11:57:34 PDT 2018
Author: hsaito
Date: Tue May 8 11:57:34 2018
New Revision: 331799
URL: http://llvm.org/viewvc/llvm-project?rev=331799&view=rev
Log:
[LV] Fix for PR37248, Broadcast codegen incorrectly assumed vector loop body is single basic block
Summary:
Broadcast code generation emitted instructions in pre-header, while the instruction they are dependent on in the vector loop body.
This resulted in an IL verification error ---- value used before defined.
Reviewers: rengolin, fhahn, hfinkel
Reviewed By: rengolin, fhahn
Subscribers: dcaballe, Ka-Ka, llvm-commits
Differential Revision: https://reviews.llvm.org/D46302
Added:
llvm/trunk/test/Transforms/LoopVectorize/pr37248.ll
Modified:
llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=331799&r1=331798&r2=331799&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Tue May 8 11:57:34 2018
@@ -1737,14 +1737,16 @@ struct LoopVectorize : public FunctionPa
//===----------------------------------------------------------------------===//
Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
- // We need to place the broadcast of invariant variables outside the loop.
+ // We need to place the broadcast of invariant variables outside the loop,
+ // but only if it's proven safe to do so. Else, broadcast will be inside
+ // vector loop body.
Instruction *Instr = dyn_cast<Instruction>(V);
- bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
- bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
-
+ bool SafeToHoist = OrigLoop->isLoopInvariant(V) &&
+ (!Instr ||
+ DT->dominates(Instr->getParent(), LoopVectorPreHeader));
// Place the code for broadcasting invariant variables in the new preheader.
IRBuilder<>::InsertPointGuard Guard(Builder);
- if (Invariant)
+ if (SafeToHoist)
Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
// Broadcast the scalar into all locations in the vector.
Added: llvm/trunk/test/Transforms/LoopVectorize/pr37248.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/pr37248.ll?rev=331799&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/pr37248.ll (added)
+++ llvm/trunk/test/Transforms/LoopVectorize/pr37248.ll Tue May 8 11:57:34 2018
@@ -0,0 +1,42 @@
+; RUN: opt -passes='loop-vectorize' -force-vector-width=2 -S < %s | FileCheck %s
+;
+; Forcing VF=2 to trigger vector code gen
+;
+; This is a test case that let's vectorizer's code gen to generate
+; more than one BasicBlocks in the loop body (emulated masked scatter)
+; for those targets that do not support masked scatter. Broadcast
+; code generation was previously dependent on loop body being
+; a single basic block and this test case exposed incorrect code gen
+; resulting in an assert in IL verification. Test passes if IL verification
+; does not fail.
+;
+; Performing minimal check in the output to ensure the loop is actually
+; vectorized.
+;
+; CHECK: vector.body
+
+ at a = external global [2 x i16], align 1
+
+define void @f1() {
+entry:
+ br label %for.body
+
+for.body: ; preds = %land.end, %entry
+ %0 = phi i32 [ undef, %entry ], [ %dec, %land.end ]
+ br i1 undef, label %land.end, label %land.rhs
+
+land.rhs: ; preds = %for.body
+ %1 = load i32, i32* undef, align 1
+ br label %land.end
+
+land.end: ; preds = %land.rhs, %for.body
+ %2 = trunc i32 %0 to i16
+ %arrayidx = getelementptr inbounds [2 x i16], [2 x i16]* @a, i16 0, i16 %2
+ store i16 undef, i16* %arrayidx, align 1
+ %dec = add nsw i32 %0, -1
+ %cmp = icmp sgt i32 %0, 1
+ br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge: ; preds = %land.end
+ unreachable
+}
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