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[RuntimeUnrolling] Populate the VMap entry correctly when default generated through lookup 

During runtime unrolling on loops with multiple exits, we update the
exit blocks with the correct phi values from both original and remainder
loop.
In this process, we lookup the VMap for the mapped incoming phi values,
but did not update the VMap if a default entry was generated in the VMap
during the lookup. This default value is generated when constants or
values outside the current loop are looked up.
This patch fixes the assertion failure when null entries are present in
the VMap because of this lookup. Added a testcase that showcases the
problem.

llvm-svn: 313358
This commit is contained in:
Anna Thomas 2017-09-15 13:29:33 +00:00
parent 2a3209ed0a
commit 512dde77ba
2 changed files with 51 additions and 3 deletions
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10
llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
View File

@ -782,11 +782,15 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
// Add the incoming values from the remainder code to the end of the phi
// node.
for (unsigned i =0; i < oldNumOperands; i++){
Value *newVal = VMap[Phi->getIncomingValue(i)];
Value *newVal = VMap.lookup(Phi->getIncomingValue(i));
// newVal can be a constant or derived from values outside the loop, and
// hence need not have a VMap value.
if (!newVal)
// hence need not have a VMap value. Also, since lookup already generated
// a default "null" VMap entry for this value, we need to populate that
// VMap entry correctly, with the mapped entry being itself.
if (!newVal) {
newVal = Phi->getIncomingValue(i);
VMap[Phi->getIncomingValue(i)] = Phi->getIncomingValue(i);
}
Phi->addIncoming(newVal,
cast<BasicBlock>(VMap[Phi->getIncomingBlock(i)]));
}

44
llvm/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
View File

@ -4,6 +4,8 @@
; RUN: opt < %s -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=false -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine -S | FileCheck %s -check-prefix=PROLOG
; RUN: opt < %s -loop-unroll -unroll-runtime -unroll-runtime-epilog=false -unroll-count=2 -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine
; REQUIRES: asserts
; the third and fifth RUNs generate an epilog/prolog remainder block for all the test
; cases below (it does not generate a loop).
@ -478,3 +480,45 @@ latch: ; preds = %innerH
exit: ; preds = %latch
ret void
}
declare i8 addrspace(1)* @foo(i32)
; inner loop prolog unrolled
; a value from outer loop is used in exit block of inner loop.
; Don't create VMap entries for such values (%trip).
define i8 addrspace(1)* @test9(i8* nocapture readonly %arg, i32 %n) {
; PROLOG: test9(
; PROLOG: header.prol:
; PROLOG-NEXT: %phi.prol = phi i64 [ 0, %header.prol.preheader ], [ %iv.next.prol, %latch.prol ]
; PROLOG: latch.prol:
; PROLOG-NOT: trip
; PROLOG: br i1 %prol.iter.cmp, label %header.prol.loopexit.unr-lcssa, label %header.prol
bb:
br label %outerloopHdr
outerloopHdr: ; preds = %outerLatch, %bb
%trip = add i32 %n, -1
%outercnd = icmp slt i32 0, %trip
br i1 %outercnd, label %preheader, label %outerLatch
preheader: ; preds = %outerloopHdr
%tmp4 = zext i32 0 to i64
br label %header
header: ; preds = %latch, %preheader
%phi = phi i64 [ %tmp4, %preheader ], [ %iv.next, %latch ]
%tmp7 = trunc i64 %phi to i32
br i1 true, label %latch, label %innerexit
innerexit: ; preds = %header
%tmp9 = call i8 addrspace(1)* @foo(i32 %trip)
ret i8 addrspace(1)* %tmp9
latch: ; preds = %header
%tmp11 = add nsw i32 %tmp7, 1
%innercnd = icmp slt i32 %tmp11, %trip
%iv.next = add nuw nsw i64 %phi, 1
br i1 %innercnd, label %header, label %outerLatch
outerLatch: ; preds = %latch, %outerloopHdr
br label %outerloopHdr
}