[llvm-commits] [llvm] r97126 - in /llvm/trunk: lib/Analysis/ScalarEvolution.cpp lib/Transforms/Scalar/IndVarSimplify.cpp lib/Transforms/Utils/LoopSimplify.cpp test/CodeGen/X86/2009-09-07-CoalescerBug.ll test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll test/Transforms/LoopDeletion/simplify-then-delete.ll
Dan Gohman
gohman at apple.com
Wed Feb 24 22:57:05 PST 2010
Author: djg
Date: Thu Feb 25 00:57:05 2010
New Revision: 97126
URL: http://llvm.org/viewvc/llvm-project?rev=97126&view=rev
Log:
Make LoopSimplify change conditional branches in loop exiting blocks
which branch on undef to branch on a boolean constant for the edge
exiting the loop. This helps ScalarEvolution compute trip counts for
loops.
Teach ScalarEvolution to recognize single-value PHIs, when safe, and
ForgetSymbolicName to forget such single-value PHI nodes as apprpriate
in ForgetSymbolicName.
Added:
llvm/trunk/test/Transforms/LoopDeletion/simplify-then-delete.ll
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp
llvm/trunk/test/CodeGen/X86/2009-09-07-CoalescerBug.ll
llvm/trunk/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=97126&r1=97125&r2=97126&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Thu Feb 25 00:57:05 2010
@@ -2549,14 +2549,14 @@
/// the Scalars map if they reference SymName. This is used during PHI
/// resolution.
void
-ScalarEvolution::ForgetSymbolicName(Instruction *I, const SCEV *SymName) {
+ScalarEvolution::ForgetSymbolicName(Instruction *PN, const SCEV *SymName) {
SmallVector<Instruction *, 16> Worklist;
- PushDefUseChildren(I, Worklist);
+ PushDefUseChildren(PN, Worklist);
SmallPtrSet<Instruction *, 8> Visited;
- Visited.insert(I);
+ Visited.insert(PN);
while (!Worklist.empty()) {
- I = Worklist.pop_back_val();
+ Instruction *I = Worklist.pop_back_val();
if (!Visited.insert(I)) continue;
std::map<SCEVCallbackVH, const SCEV *>::iterator It =
@@ -2568,12 +2568,15 @@
continue;
// SCEVUnknown for a PHI either means that it has an unrecognized
- // structure, or it's a PHI that's in the progress of being computed
- // by createNodeForPHI. In the former case, additional loop trip
- // count information isn't going to change anything. In the later
- // case, createNodeForPHI will perform the necessary updates on its
- // own when it gets to that point.
- if (!isa<PHINode>(I) || !isa<SCEVUnknown>(It->second)) {
+ // structure, it's a PHI that's in the progress of being computed
+ // by createNodeForPHI, or it's a single-value PHI. In the first case,
+ // additional loop trip count information isn't going to change anything.
+ // In the second case, createNodeForPHI will perform the necessary
+ // updates on its own when it gets to that point. In the third, we do
+ // want to forget the SCEVUnknown.
+ if (!isa<PHINode>(I) ||
+ !isa<SCEVUnknown>(It->second) ||
+ (I != PN && It->second == SymName)) {
ValuesAtScopes.erase(It->second);
Scalars.erase(It);
}
@@ -2696,9 +2699,21 @@
return SymbolicName;
}
- // It's tempting to recognize PHIs with a unique incoming value, however
- // this leads passes like indvars to break LCSSA form. Fortunately, such
- // PHIs are rare, as instcombine zaps them.
+ // If the PHI has a single incoming value, follow that value, unless the
+ // PHI's incoming blocks are in a different loop, in which case doing so
+ // risks breaking LCSSA form. Instcombine would normally zap these, but
+ // it doesn't have DominatorTree information, so it may miss cases.
+ if (Value *V = PN->hasConstantValue(DT)) {
+ bool AllSameLoop = true;
+ Loop *PNLoop = LI->getLoopFor(PN->getParent());
+ for (size_t i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (LI->getLoopFor(PN->getIncomingBlock(i)) != PNLoop) {
+ AllSameLoop = false;
+ break;
+ }
+ if (AllSameLoop)
+ return getSCEV(V);
+ }
// If it's not a loop phi, we can't handle it yet.
return getUnknown(PN);
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=97126&r1=97125&r2=97126&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Thu Feb 25 00:57:05 2010
@@ -384,17 +384,18 @@
// in this loop, insert a canonical induction variable of the largest size.
Value *IndVar = 0;
if (NeedCannIV) {
- // Check to see if the loop already has a canonical-looking induction
- // variable. If one is present and it's wider than the planned canonical
- // induction variable, temporarily remove it, so that the Rewriter
- // doesn't attempt to reuse it.
- PHINode *OldCannIV = L->getCanonicalInductionVariable();
- if (OldCannIV) {
+ // Check to see if the loop already has any canonical-looking induction
+ // variables. If any are present and wider than the planned canonical
+ // induction variable, temporarily remove them, so that the Rewriter
+ // doesn't attempt to reuse them.
+ SmallVector<PHINode *, 2> OldCannIVs;
+ while (PHINode *OldCannIV = L->getCanonicalInductionVariable()) {
if (SE->getTypeSizeInBits(OldCannIV->getType()) >
SE->getTypeSizeInBits(LargestType))
OldCannIV->removeFromParent();
else
- OldCannIV = 0;
+ break;
+ OldCannIVs.push_back(OldCannIV);
}
IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L, LargestType);
@@ -404,17 +405,21 @@
DEBUG(dbgs() << "INDVARS: New CanIV: " << *IndVar << '\n');
// Now that the official induction variable is established, reinsert
- // the old canonical-looking variable after it so that the IR remains
- // consistent. It will be deleted as part of the dead-PHI deletion at
+ // any old canonical-looking variables after it so that the IR remains
+ // consistent. They will be deleted as part of the dead-PHI deletion at
// the end of the pass.
- if (OldCannIV)
- OldCannIV->insertAfter(cast<Instruction>(IndVar));
+ while (!OldCannIVs.empty()) {
+ PHINode *OldCannIV = OldCannIVs.pop_back_val();
+ OldCannIV->insertBefore(L->getHeader()->getFirstNonPHI());
+ }
}
// If we have a trip count expression, rewrite the loop's exit condition
// using it. We can currently only handle loops with a single exit.
ICmpInst *NewICmp = 0;
- if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount) && ExitingBlock) {
+ if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount) &&
+ !BackedgeTakenCount->isZero() &&
+ ExitingBlock) {
assert(NeedCannIV &&
"LinearFunctionTestReplace requires a canonical induction variable");
// Can't rewrite non-branch yet.
Modified: llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp?rev=97126&r1=97125&r2=97126&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopSimplify.cpp Thu Feb 25 00:57:05 2010
@@ -159,6 +159,22 @@
}
}
+ // If there are exiting blocks with branches on undef, resolve the undef in
+ // the direction which will exit the loop. This will help simplify loop
+ // trip count computations.
+ SmallVector<BasicBlock*, 8> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
+ for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(),
+ E = ExitingBlocks.end(); I != E; ++I)
+ if (BranchInst *BI = dyn_cast<BranchInst>((*I)->getTerminator()))
+ if (BI->isConditional()) {
+ if (UndefValue *Cond = dyn_cast<UndefValue>(BI->getCondition())) {
+ BI->setCondition(ConstantInt::get(Cond->getType(),
+ !L->contains(BI->getSuccessor(0))));
+ Changed = true;
+ }
+ }
+
// Does the loop already have a preheader? If so, don't insert one.
BasicBlock *Preheader = L->getLoopPreheader();
if (!Preheader) {
@@ -250,8 +266,6 @@
break;
}
if (UniqueExit) {
- SmallVector<BasicBlock*, 8> ExitingBlocks;
- L->getExitingBlocks(ExitingBlocks);
for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
BasicBlock *ExitingBlock = ExitingBlocks[i];
if (!ExitingBlock->getSinglePredecessor()) continue;
Modified: llvm/trunk/test/CodeGen/X86/2009-09-07-CoalescerBug.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/2009-09-07-CoalescerBug.ll?rev=97126&r1=97125&r2=97126&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/2009-09-07-CoalescerBug.ll (original)
+++ llvm/trunk/test/CodeGen/X86/2009-09-07-CoalescerBug.ll Thu Feb 25 00:57:05 2010
@@ -8,8 +8,7 @@
define i64 @hammer_time(i64 %modulep, i64 %physfree) nounwind ssp noredzone noimplicitfloat {
; CHECK: hammer_time:
; CHECK: movq $Xrsvd, %rax
-; CHECK: movq $Xrsvd, %rsi
-; CHECK: movq $Xrsvd, %rdi
+; CHECK: movq $Xrsvd, %rcx
entry:
br i1 undef, label %if.then, label %if.end
Modified: llvm/trunk/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll?rev=97126&r1=97125&r2=97126&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll Thu Feb 25 00:57:05 2010
@@ -7,7 +7,7 @@
LoopHead: ; preds = %LoopHead, %0, %0
%A = phi i32 [ 7, %0 ], [ 7, %0 ], [ %B, %LoopHead ] ; <i32> [#uses=1]
%B = add i32 %A, 1 ; <i32> [#uses=2]
- br i1 undef, label %LoopHead, label %Out
+ br i1 true, label %LoopHead, label %Out
Out: ; preds = %LoopHead
ret i32 %B
Added: llvm/trunk/test/Transforms/LoopDeletion/simplify-then-delete.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopDeletion/simplify-then-delete.ll?rev=97126&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopDeletion/simplify-then-delete.ll (added)
+++ llvm/trunk/test/Transforms/LoopDeletion/simplify-then-delete.ll Thu Feb 25 00:57:05 2010
@@ -0,0 +1,65 @@
+; RUN: opt < %s -S -indvars -loop-deletion -simplifycfg | FileCheck %s
+; PR5794
+
+; Indvars and loop deletion should be able to eliminate all looping
+; in this testcase.
+
+; CHECK: define i32 @pmat(i32 %m, i32 %n, double* %y) nounwind {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: ret i32 0
+; CHECK-NEXT: }
+
+target datalayout = "e-p:64:64:64"
+
+define i32 @pmat(i32 %m, i32 %n, double* %y) nounwind {
+entry:
+ %cmp4 = icmp sgt i32 %m, 0
+ br i1 %cmp4, label %bb.n10, label %w.e12
+
+w.c:
+ %cmp = icmp slt i32 %inc11, %m
+ br i1 %cmp, label %w.c2.p, label %w.c.w.e12c
+
+w.c.w.e12c:
+ br label %w.c.w.e12c.s
+
+w.c.w.e12c.s:
+ br label %w.e12
+
+bb.n10:
+ %cmp51 = icmp sgt i32 %n, 0
+ br i1 %cmp51, label %bb.n10.w.c.w.e12c.sc, label %bb.n10.bb.n10.sc
+
+bb.n10.bb.n10.sc:
+ br label %bb.n10.s
+
+bb.n10.w.c.w.e12c.sc:
+ br label %w.c.w.e12c.s
+
+bb.n10.s:
+ br label %w.c2.p
+
+w.c2.p:
+ %i.05 = phi i32 [ 0, %bb.n10.s ], [ %inc11, %w.c ]
+ br i1 false, label %bb.n, label %w.e
+
+w.c2:
+ br i1 undef, label %w.b6, label %w.c2.w.ec
+
+w.c2.w.ec:
+ br label %w.e
+
+bb.n:
+ br label %w.b6
+
+w.b6:
+ br label %w.c2
+
+w.e:
+ %i.08 = phi i32 [ undef, %w.c2.w.ec ], [ %i.05, %w.c2.p ]
+ %inc11 = add nsw i32 %i.08, 1
+ br label %w.c
+
+w.e12:
+ ret i32 0
+}
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