[llvm] r275217 - [LV] Remove wrong assumption about LCSSA
Michael Kuperstein via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 12 14:24:06 PDT 2016
Author: mkuper
Date: Tue Jul 12 16:24:06 2016
New Revision: 275217
URL: http://llvm.org/viewvc/llvm-project?rev=275217&view=rev
Log:
[LV] Remove wrong assumption about LCSSA
The LCSSA pass itself will not generate several redundant PHI nodes in a single
exit block. However, such redundant PHI nodes don't violate LCSSA form, and may
be introduced by passes that preserve LCSSA, and/or preserved by the LCSSA pass
itself. So, assuming a single PHI node per exit block is not safe.
Modified:
llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
llvm/trunk/test/Transforms/LoopVectorize/iv_outside_user.ll
Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=275217&r1=275216&r2=275217&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Tue Jul 12 16:24:06 2016
@@ -3112,9 +3112,6 @@ void InnerLoopVectorizer::fixupIVUsers(P
// value (the value that feeds into the phi from the loop latch).
// We allow both, but they, obviously, have different values.
- // We only expect at most one of each kind of user. This is because LCSSA will
- // canonicalize the users to a single PHI node per exit block, and we
- // currently only vectorize loops with a single exit.
assert(OrigLoop->getExitBlock() && "Expected a single exit block");
// An external user of the last iteration's value should see the value that
@@ -3132,7 +3129,6 @@ void InnerLoopVectorizer::fixupIVUsers(P
auto *User = cast<PHINode>(UI);
if (User->getBasicBlockIndex(MiddleBlock) == -1)
User->addIncoming(EndValue, MiddleBlock);
- break;
}
}
@@ -3159,7 +3155,6 @@ void InnerLoopVectorizer::fixupIVUsers(P
Value *Escape = II.transform(B, CMO, PSE.getSE(), DL);
Escape->setName("ind.escape");
User->addIncoming(Escape, MiddleBlock);
- break;
}
}
}
Modified: llvm/trunk/test/Transforms/LoopVectorize/iv_outside_user.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/iv_outside_user.ll?rev=275217&r1=275216&r2=275217&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/iv_outside_user.ll (original)
+++ llvm/trunk/test/Transforms/LoopVectorize/iv_outside_user.ll Tue Jul 12 16:24:06 2016
@@ -108,3 +108,28 @@ for.body:
for.end:
ret i32* %inc.lag1
}
+
+; CHECK-LABEL: @multiphi
+; CHECK-LABEL: scalar.ph:
+; CHECK: %bc.resume.val = phi i32 [ %n.vec, %middle.block ], [ 0, %entry ]
+; CHECK-LABEL: for.end:
+; CHECK: %phi = phi i32 [ {{.*}}, %for.body ], [ %n.vec, %middle.block ]
+; CHECK: %phi2 = phi i32 [ {{.*}}, %for.body ], [ %n.vec, %middle.block ]
+; CHECK: store i32 %phi2, i32* %p
+; CHECK: ret i32 %phi
+define i32 @multiphi(i32 %k, i32* %p) {
+entry:
+ br label %for.body
+
+for.body:
+ %inc.phi = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+ %inc = add nsw i32 %inc.phi, 1
+ %cmp = icmp eq i32 %inc, %k
+ br i1 %cmp, label %for.end, label %for.body
+
+for.end:
+ %phi = phi i32 [ %inc, %for.body ]
+ %phi2 = phi i32 [ %inc, %for.body ]
+ store i32 %phi2, i32* %p
+ ret i32 %phi
+}
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