[llvm-commits] [llvm] r61082 - in /llvm/trunk: lib/Analysis/ScalarEvolution.cpp test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll test/Analysis/ScalarEvolution/2008-12-14-StrideAndSigned.ll test/Analysis/ScalarEvolution/2008-12-15-DontUseSDiv.ll
Nick Lewycky
nicholas at mxc.ca
Tue Dec 16 00:30:09 PST 2008
Author: nicholas
Date: Tue Dec 16 02:30:01 2008
New Revision: 61082
URL: http://llvm.org/viewvc/llvm-project?rev=61082&view=rev
Log:
Generalize support for analyzing loops to include SLE/SGE loop exit conditions
and support for non-unit strides with signed exit conditions.
Added:
llvm/trunk/test/Analysis/ScalarEvolution/2008-12-14-StrideAndSigned.ll
llvm/trunk/test/Analysis/ScalarEvolution/2008-12-15-DontUseSDiv.ll
Modified:
llvm/trunk/lib/Analysis/ScalarEvolution.cpp
llvm/trunk/test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll
llvm/trunk/test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll
Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=61082&r1=61081&r2=61082&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Tue Dec 16 02:30:01 2008
@@ -2924,15 +2924,16 @@
if (!R)
return true;
- if (isSigned)
- return true; // XXX: because we don't have an sdiv scev.
-
// If negative, it wraps around every iteration, but we don't care about that.
APInt S = SC->getValue()->getValue().abs();
- APInt Dist = APInt::getMaxValue(R->getValue()->getBitWidth()) -
- R->getValue()->getValue();
+ uint32_t Width = R->getValue()->getBitWidth();
+ APInt Dist = (isSigned ? APInt::getSignedMaxValue(Width)
+ : APInt::getMaxValue(Width))
+ - R->getValue()->getValue();
+ // Because we're looking at distance, we perform an unsigned comparison,
+ // regardless of the sign of the computation.
if (trueWhenEqual)
return !S.ult(Dist);
else
@@ -2961,24 +2962,15 @@
// m. So, we count the number of iterations in which {n,+,s} < m is true.
// Note that we cannot simply return max(m-n,0)/s because it's not safe to
// treat m-n as signed nor unsigned due to overflow possibility.
+ //
+ // Assuming that the loop will run at least once, we know that it will
+ // run (m-n)/s times.
// First, we get the value of the LHS in the first iteration: n
SCEVHandle Start = AddRec->getOperand(0);
SCEVHandle One = SE.getIntegerSCEV(1, RHS->getType());
- // Assuming that the loop will run at least once, we know that it will
- // run (m-n)/s times.
- SCEVHandle End = RHS;
-
- if (!executesAtLeastOnce(L, isSigned, trueWhenEqual,
- SE.getMinusSCEV(Start, One), RHS)) {
- // If not, we get the value of the LHS in the first iteration in which
- // the above condition doesn't hold. This equals to max(m,n).
- End = isSigned ? SE.getSMaxExpr(RHS, Start)
- : SE.getUMaxExpr(RHS, Start);
- }
-
// If the expression is less-than-or-equal to, we need to extend the
// loop by one iteration.
//
@@ -2986,16 +2978,23 @@
// might not divide cleanly. For example, if you have {2,+,5} u< 10 the
// division would equal one, but the loop runs twice putting the
// induction variable at 12.
-
+ SCEVHandle End = SE.getAddExpr(RHS, Stride);
if (!trueWhenEqual)
- // (Stride - 1) is correct only because we know it's unsigned.
- // What we really want is to decrease the magnitude of Stride by one.
- Start = SE.getMinusSCEV(Start, SE.getMinusSCEV(Stride, One));
- else
- Start = SE.getMinusSCEV(Start, Stride);
+ End = SE.getMinusSCEV(End, One);
+
+ if (!executesAtLeastOnce(L, isSigned, trueWhenEqual,
+ SE.getMinusSCEV(Start, One), RHS)) {
+ // If not, we get the value of the LHS in the first iteration in which
+ // the above condition doesn't hold. This equals to max(m,n).
+ End = isSigned ? SE.getSMaxExpr(End, Start)
+ : SE.getUMaxExpr(End, Start);
+ }
// Finally, we subtract these two values to get the number of times the
- // backedge is executed: max(m,n)-n.
+ // backedge is executed: (max(m,n)-n)/s.
+ //
+ // Note that a trip count is always positive. Using SDiv here produces
+ // wrong answers when Start < End.
return SE.getUDivExpr(SE.getMinusSCEV(End, Start), Stride);
}
Modified: llvm/trunk/test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll?rev=61082&r1=61081&r2=61082&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll (original)
+++ llvm/trunk/test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll Tue Dec 16 02:30:01 2008
@@ -1,5 +1,4 @@
; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {255 iterations}
-; XFAIL: *
define i32 @foo(i32 %x, i32 %y, i32* %lam, i32* %alp) nounwind {
bb1.thread:
Modified: llvm/trunk/test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll?rev=61082&r1=61081&r2=61082&view=diff
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll (original)
+++ llvm/trunk/test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll Tue Dec 16 02:30:01 2008
@@ -1,5 +1,4 @@
; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {0 smax}
-; XFAIL: *
define i32 @f(i32 %c.idx.val) {
Added: llvm/trunk/test/Analysis/ScalarEvolution/2008-12-14-StrideAndSigned.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/2008-12-14-StrideAndSigned.ll?rev=61082&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/2008-12-14-StrideAndSigned.ll (added)
+++ llvm/trunk/test/Analysis/ScalarEvolution/2008-12-14-StrideAndSigned.ll Tue Dec 16 02:30:01 2008
@@ -0,0 +1,21 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution |& \
+; RUN: grep {(((-1 \\* %i0) + (100005 smax %i0)) /u 5)}
+
+define i32 @foo0(i32 %i0) nounwind {
+entry:
+ br label %bb1
+
+bb: ; preds = %bb1
+ %0 = add i32 %j.0, 1 ; <i32> [#uses=1]
+ %1 = add i32 %i.0, 5 ; <i32> [#uses=1]
+ br label %bb1
+
+bb1: ; preds = %bb, %entry
+ %j.0 = phi i32 [ 0, %entry ], [ %0, %bb ] ; <i32> [#uses=2]
+ %i.0 = phi i32 [ %i0, %entry ], [ %1, %bb ] ; <i32> [#uses=2]
+ %2 = icmp sgt i32 %i.0, 100000 ; <i1> [#uses=1]
+ br i1 %2, label %return, label %bb
+
+return: ; preds = %bb1
+ ret i32 %j.0
+}
Added: llvm/trunk/test/Analysis/ScalarEvolution/2008-12-15-DontUseSDiv.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/ScalarEvolution/2008-12-15-DontUseSDiv.ll?rev=61082&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/2008-12-15-DontUseSDiv.ll (added)
+++ llvm/trunk/test/Analysis/ScalarEvolution/2008-12-15-DontUseSDiv.ll Tue Dec 16 02:30:01 2008
@@ -0,0 +1,20 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution |& grep {/u 5}
+
+define i8 @foo0(i8 %i0) nounwind {
+entry:
+ br label %bb1
+
+bb: ; preds = %bb1
+ %0 = add i8 %j.0, 1 ; <i8> [#uses=1]
+ %1 = add i8 %i.0, 5 ; <i8> [#uses=1]
+ br label %bb1
+
+bb1: ; preds = %bb, %entry
+ %j.0 = phi i8 [ 0, %entry ], [ %0, %bb ] ; <i8> [#uses=2]
+ %i.0 = phi i8 [ %i0, %entry ], [ %1, %bb ] ; <i8> [#uses=2]
+ %2 = icmp sgt i8 %i.0, 100 ; <i1> [#uses=1]
+ br i1 %2, label %return, label %bb
+
+return: ; preds = %bb1
+ ret i8 %j.0
+}
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