[llvm-commits] [llvm] r107224 - in /llvm/trunk: lib/Analysis/ScalarEvolution.cpp test/Transforms/IndVarSimplify/tripcount_compute.ll
Dan Gohman
gohman at apple.com
Tue Jun 29 16:43:07 PDT 2010
Author: djg
Date: Tue Jun 29 18:43:06 2010
New Revision: 107224
URL: http://llvm.org/viewvc/llvm-project?rev=107224&view=rev
Log:
Fix ScalarEvolution's tripcount computation for chains of loops
where each loop's induction variable's start value is the exit
value of a preceding loop.
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/test/Transforms/IndVarSimplify/tripcount_compute.ll
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=107224&r1=107223&r2=107224&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Tue Jun 29 18:43:06 2010
@@ -4337,54 +4337,51 @@
// the arguments into constants, and if so, try to constant propagate the
// result. This is particularly useful for computing loop exit values.
if (CanConstantFold(I)) {
- std::vector<Constant*> Operands;
- Operands.reserve(I->getNumOperands());
+ SmallVector<Constant *, 4> Operands;
+ bool MadeImprovement = false;
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
Value *Op = I->getOperand(i);
if (Constant *C = dyn_cast<Constant>(Op)) {
Operands.push_back(C);
- } else {
- // If any of the operands is non-constant and if they are
- // non-integer and non-pointer, don't even try to analyze them
- // with scev techniques.
- if (!isSCEVable(Op->getType()))
- return V;
-
- const SCEV *OpV = getSCEVAtScope(Op, L);
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV)) {
- Constant *C = SC->getValue();
- if (C->getType() != Op->getType())
- C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
- Op->getType(),
- false),
- C, Op->getType());
- Operands.push_back(C);
- } else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV)) {
- if (Constant *C = dyn_cast<Constant>(SU->getValue())) {
- if (C->getType() != Op->getType())
- C =
- ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
- Op->getType(),
- false),
- C, Op->getType());
- Operands.push_back(C);
- } else
- return V;
- } else {
- return V;
- }
+ continue;
}
+
+ // If any of the operands is non-constant and if they are
+ // non-integer and non-pointer, don't even try to analyze them
+ // with scev techniques.
+ if (!isSCEVable(Op->getType()))
+ return V;
+
+ const SCEV *OrigV = getSCEV(Op);
+ const SCEV *OpV = getSCEVAtScope(OrigV, L);
+ MadeImprovement |= OrigV != OpV;
+
+ Constant *C = 0;
+ if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OpV))
+ C = SC->getValue();
+ if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(OpV))
+ C = dyn_cast<Constant>(SU->getValue());
+ if (!C) return V;
+ if (C->getType() != Op->getType())
+ C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
+ Op->getType(),
+ false),
+ C, Op->getType());
+ Operands.push_back(C);
}
- Constant *C = 0;
- if (const CmpInst *CI = dyn_cast<CmpInst>(I))
- C = ConstantFoldCompareInstOperands(CI->getPredicate(),
- Operands[0], Operands[1], TD);
- else
- C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
- &Operands[0], Operands.size(), TD);
- if (C)
+ // Check to see if getSCEVAtScope actually made an improvement.
+ if (MadeImprovement) {
+ Constant *C = 0;
+ if (const CmpInst *CI = dyn_cast<CmpInst>(I))
+ C = ConstantFoldCompareInstOperands(CI->getPredicate(),
+ Operands[0], Operands[1], TD);
+ else
+ C = ConstantFoldInstOperands(I->getOpcode(), I->getType(),
+ &Operands[0], Operands.size(), TD);
+ if (!C) return V;
return getSCEV(C);
+ }
}
}
@@ -4434,7 +4431,29 @@
// If this is a loop recurrence for a loop that does not contain L, then we
// are dealing with the final value computed by the loop.
if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
- if (!L || !AddRec->getLoop()->contains(L)) {
+ // First, attempt to evaluate each operand.
+ // Avoid performing the look-up in the common case where the specified
+ // expression has no loop-variant portions.
+ for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
+ const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
+ if (OpAtScope == AddRec->getOperand(i))
+ continue;
+
+ // Okay, at least one of these operands is loop variant but might be
+ // foldable. Build a new instance of the folded commutative expression.
+ SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
+ AddRec->op_begin()+i);
+ NewOps.push_back(OpAtScope);
+ for (++i; i != e; ++i)
+ NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
+
+ AddRec = cast<SCEVAddRecExpr>(getAddRecExpr(NewOps, AddRec->getLoop()));
+ break;
+ }
+
+ // If the scope is outside the addrec's loop, evaluate it by using the
+ // loop exit value of the addrec.
+ if (!AddRec->getLoop()->contains(L)) {
// To evaluate this recurrence, we need to know how many times the AddRec
// loop iterates. Compute this now.
const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
@@ -4443,6 +4462,7 @@
// Then, evaluate the AddRec.
return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
}
+
return AddRec;
}
Modified: llvm/trunk/test/Transforms/IndVarSimplify/tripcount_compute.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/tripcount_compute.ll?rev=107224&r1=107223&r2=107224&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/tripcount_compute.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/tripcount_compute.ll Tue Jun 29 18:43:06 2010
@@ -1,9 +1,12 @@
+; RUN: opt < %s -indvars -S | FileCheck %s
+
; These tests ensure that we can compute the trip count of various forms of
; loops. If the trip count of the loop is computable, then we will know what
; the exit value of the loop will be for some value, allowing us to substitute
; it directly into users outside of the loop, making the loop dead.
-;
-; RUN: opt < %s -indvars -loop-deletion -simplifycfg -S | not grep br
+
+; CHECK: @linear_setne
+; CHECK: ret i32 100
define i32 @linear_setne() {
entry:
@@ -19,6 +22,9 @@
ret i32 %i
}
+; CHECK: @linear_setne_2
+; CHECK: ret i32 100
+
define i32 @linear_setne_2() {
entry:
br label %loop
@@ -33,6 +39,9 @@
ret i32 %i
}
+; CHECK: @linear_setne_overflow
+; CHECK: ret i32 0
+
define i32 @linear_setne_overflow() {
entry:
br label %loop
@@ -47,6 +56,9 @@
ret i32 %i
}
+; CHECK: @linear_setlt
+; CHECK: ret i32 100
+
define i32 @linear_setlt() {
entry:
br label %loop
@@ -61,6 +73,9 @@
ret i32 %i
}
+; CHECK: @quadratic_setlt
+; CHECK: ret i32 34
+
define i32 @quadratic_setlt() {
entry:
br label %loop
@@ -76,6 +91,9 @@
ret i32 %i
}
+; CHECK: @chained
+; CHECK: ret i32 200
+
define i32 @chained() {
entry:
br label %loop
@@ -98,3 +116,47 @@
loopexit2: ; preds = %loop2
ret i32 %j
}
+
+; CHECK: @chained4
+; CHECK: ret i32 400
+
+define i32 @chained4() {
+entry:
+ br label %loop
+
+loop: ; preds = %loop, %entry
+ %i = phi i32 [ 0, %entry ], [ %i.next, %loop ] ; <i32> [#uses=3]
+ %i.next = add i32 %i, 1 ; <i32> [#uses=1]
+ %c = icmp ne i32 %i.next, 100 ; <i1> [#uses=1]
+ br i1 %c, label %loop, label %loopexit
+
+loopexit: ; preds = %loop
+ br label %loop2
+
+loop2: ; preds = %loop2, %loopexit
+ %j = phi i32 [ %i.next, %loopexit ], [ %j.next, %loop2 ] ; <i32> [#uses=3]
+ %j.next = add i32 %j, 1 ; <i32> [#uses=1]
+ %c2 = icmp ne i32 %j.next, 200 ; <i1> [#uses=1]
+ br i1 %c2, label %loop2, label %loopexit2
+
+loopexit2: ; preds = %loop
+ br label %loop8
+
+loop8: ; preds = %loop2, %loopexit
+ %k = phi i32 [ %j.next, %loopexit2 ], [ %k.next, %loop8 ] ; <i32> [#uses=3]
+ %k.next = add i32 %k, 1 ; <i32> [#uses=1]
+ %c8 = icmp ne i32 %k.next, 300 ; <i1> [#uses=1]
+ br i1 %c8, label %loop8, label %loopexit8
+
+loopexit8: ; preds = %loop2
+ br label %loop9
+
+loop9: ; preds = %loop2, %loopexit
+ %l = phi i32 [ %k.next, %loopexit8 ], [ %l.next, %loop9 ] ; <i32> [#uses=3]
+ %l.next = add i32 %l, 1 ; <i32> [#uses=1]
+ %c9 = icmp ne i32 %l.next, 400 ; <i1> [#uses=1]
+ br i1 %c9, label %loop9, label %loopexit9
+
+loopexit9: ; preds = %loop2
+ ret i32 %l.next
+}
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