Generalize LSR's OptimizeSMax to handle unsigned max tests as well

as signed max tests. Along with r73717, this helps CodeGen avoid
emitting code for a maximum operation for this class of loop.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73718 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 340 insertions, 31 deletions

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 03966672d6..ad9235a18e 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -143,10 +143,10 @@ namespace {
     /// inside the loop then try to eliminate the cast opeation.
     void OptimizeShadowIV(Loop *L);
 
-    /// OptimizeSMax - Rewrite the loop's terminating condition
-    /// if it uses an smax computation.
-    ICmpInst *OptimizeSMax(Loop *L, ICmpInst *Cond,
-                           IVStrideUse* &CondUse);
+    /// OptimizeMax - Rewrite the loop's terminating condition
+    /// if it uses a max computation.
+    ICmpInst *OptimizeMax(Loop *L, ICmpInst *Cond,
+                          IVStrideUse* &CondUse);
 
     bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
                            const SCEVHandle *&CondStride);
@@ -2044,8 +2044,8 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
   return Cond;
 }
 
-/// OptimizeSMax - Rewrite the loop's terminating condition if it uses
-/// an smax computation.
+/// OptimizeMax - Rewrite the loop's terminating condition if it uses
+/// a max computation.
 ///
 /// This is a narrow solution to a specific, but acute, problem. For loops
 /// like this:
@@ -2055,10 +2055,10 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
 ///     p[i] = 0.0;
 ///   } while (++i < n);
 ///
-/// where the comparison is signed, the trip count isn't just 'n', because
-/// 'n' could be negative. And unfortunately this can come up even for loops
-/// where the user didn't use a C do-while loop. For example, seemingly
-/// well-behaved top-test loops will commonly be lowered like this:
+/// the trip count isn't just 'n', because 'n' might not be positive. And
+/// unfortunately this can come up even for loops where the user didn't use
+/// a C do-while loop. For example, seemingly well-behaved top-test loops
+/// will commonly be lowered like this:
 //
 ///   if (n > 0) {
 ///     i = 0;
@@ -2071,14 +2071,14 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
 /// test in such a way that indvars can't find it.
 ///
 /// When indvars can't find the if test in loops like this, it creates a
-/// signed-max expression, which allows it to give the loop a canonical
+/// max expression, which allows it to give the loop a canonical
 /// induction variable:
 ///
 ///   i = 0;
-///   smax = n < 1 ? 1 : n;
+///   max = n < 1 ? 1 : n;
 ///   do {
 ///     p[i] = 0.0;
-///   } while (++i != smax);
+///   } while (++i != max);
 ///
 /// Canonical induction variables are necessary because the loop passes
 /// are designed around them. The most obvious example of this is the
@@ -2094,8 +2094,8 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
 /// the instructions for the maximum computation.
 ///
-ICmpInst *LoopStrengthReduce::OptimizeSMax(Loop *L, ICmpInst *Cond,
-                                           IVStrideUse* &CondUse) {
+ICmpInst *LoopStrengthReduce::OptimizeMax(Loop *L, ICmpInst *Cond,
+                                          IVStrideUse* &CondUse) {
   // Check that the loop matches the pattern we're looking for.
   if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
       Cond->getPredicate() != CmpInst::ICMP_NE)
@@ -2113,12 +2113,14 @@ ICmpInst *LoopStrengthReduce::OptimizeSMax(Loop *L, ICmpInst *Cond,
   SCEVHandle IterationCount = SE->getAddExpr(BackedgeTakenCount, One);
 
   // Check for a max calculation that matches the pattern.
-  const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(IterationCount);
-  if (!SMax || SMax != SE->getSCEV(Sel)) return Cond;
+  if (!isa<SCEVSMaxExpr>(IterationCount) && !isa<SCEVUMaxExpr>(IterationCount))
+    return Cond;
+  const SCEVNAryExpr *Max = cast<SCEVNAryExpr>(IterationCount);
+  if (Max != SE->getSCEV(Sel)) return Cond;
 
-  SCEVHandle SMaxLHS = SMax->getOperand(0);
-  SCEVHandle SMaxRHS = SMax->getOperand(1);
-  if (!SMaxLHS || SMaxLHS != One) return Cond;
+  SCEVHandle MaxLHS = Max->getOperand(0);
+  SCEVHandle MaxRHS = Max->getOperand(1);
+  if (!MaxLHS || MaxLHS != One) return Cond;
 
   // Check the relevant induction variable for conformance to
   // the pattern.
@@ -2135,19 +2137,23 @@ ICmpInst *LoopStrengthReduce::OptimizeSMax(Loop *L, ICmpInst *Cond,
   // Check the right operand of the select, and remember it, as it will
   // be used in the new comparison instruction.
   Value *NewRHS = 0;
-  if (SE->getSCEV(Sel->getOperand(1)) == SMaxRHS)
+  if (SE->getSCEV(Sel->getOperand(1)) == MaxRHS)
     NewRHS = Sel->getOperand(1);
-  else if (SE->getSCEV(Sel->getOperand(2)) == SMaxRHS)
+  else if (SE->getSCEV(Sel->getOperand(2)) == MaxRHS)
     NewRHS = Sel->getOperand(2);
   if (!NewRHS) return Cond;
 
+  // Determine the new comparison opcode. It may be signed or unsigned,
+  // and the original comparison may be either equality or inequality.
+  CmpInst::Predicate Pred =
+    isa<SCEVSMaxExpr>(Max) ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT;
+  if (Cond->getPredicate() == CmpInst::ICMP_EQ)
+    Pred = CmpInst::getInversePredicate(Pred);
+
   // Ok, everything looks ok to change the condition into an SLT or SGE and
   // delete the max calculation.
   ICmpInst *NewCond =
-    new ICmpInst(Cond->getPredicate() == CmpInst::ICMP_NE ?
-                   CmpInst::ICMP_SLT :
-                   CmpInst::ICMP_SGE,
-                 Cond->getOperand(0), NewRHS, "scmp", Cond);
+    new ICmpInst(Pred, Cond->getOperand(0), NewRHS, "scmp", Cond);
 
   // Delete the max calculation instructions.
   Cond->replaceAllUsesWith(NewCond);
@@ -2360,10 +2366,10 @@ void LoopStrengthReduce::OptimizeLoopTermCond(Loop *L) {
     StrideNoReuse.insert(*CondStride);
   }
 
-  // If the trip count is computed in terms of an smax (due to ScalarEvolution
+  // If the trip count is computed in terms of a max (due to ScalarEvolution
   // being unable to find a sufficient guard, for example), change the loop
-  // comparison to use SLT instead of NE.
-  Cond = OptimizeSMax(L, Cond, CondUse);
+  // comparison to use SLT or ULT instead of NE.
+  Cond = OptimizeMax(L, Cond, CondUse);
 
   // If possible, change stride and operands of the compare instruction to
   // eliminate one stride.
diff --git a/test/CodeGen/X86/optimize-smax.ll b/test/CodeGen/X86/optimize-max-0.ll
index 0c3be31e29..90c14565e9 100644
--- a/test/CodeGen/X86/optimize-smax.ll
+++ b/test/CodeGen/X86/optimize-max-0.ll
@@ -1,7 +1,7 @@
 ; RUN: llvm-as < %s | llc -march=x86 | not grep cmov
 
-; LSR should be able to eliminate the smax computations by
-; making the loops use slt comparisons instead of ne comparisons.
+; LSR should be able to eliminate the max computations by
+; making the loops use slt/ult comparisons instead of ne comparisons.
 
 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
 target triple = "i386-apple-darwin9"
@@ -231,6 +231,231 @@ return:		; preds = %bb20
 	ret void
 }
 
+define void @bar(i8* %r, i32 %s, i32 %w, i32 %x, i8* %j, i32 %d) nounwind {
+entry:
+	%0 = mul i32 %x, %w		; <i32> [#uses=2]
+	%1 = mul i32 %x, %w		; <i32> [#uses=1]
+	%2 = udiv i32 %1, 4		; <i32> [#uses=1]
+	%.sum2 = add i32 %2, %0		; <i32> [#uses=2]
+	%cond = icmp eq i32 %d, 1		; <i1> [#uses=1]
+	br i1 %cond, label %bb29, label %bb10.preheader
+
+bb10.preheader:		; preds = %entry
+	%3 = icmp ne i32 %x, 0		; <i1> [#uses=1]
+	br i1 %3, label %bb.nph9, label %bb18.loopexit
+
+bb.nph7:		; preds = %bb7.preheader
+	%4 = mul i32 %y.08, %w		; <i32> [#uses=1]
+	%5 = mul i32 %y.08, %s		; <i32> [#uses=1]
+	%6 = add i32 %5, 1		; <i32> [#uses=1]
+	%tmp8 = icmp ugt i32 1, %w		; <i1> [#uses=1]
+	%smax9 = select i1 %tmp8, i32 1, i32 %w		; <i32> [#uses=1]
+	br label %bb6
+
+bb6:		; preds = %bb7, %bb.nph7
+	%x.06 = phi i32 [ 0, %bb.nph7 ], [ %indvar.next7, %bb7 ]		; <i32> [#uses=3]
+	%7 = add i32 %x.06, %4		; <i32> [#uses=1]
+	%8 = shl i32 %x.06, 1		; <i32> [#uses=1]
+	%9 = add i32 %6, %8		; <i32> [#uses=1]
+	%10 = getelementptr i8* %r, i32 %9		; <i8*> [#uses=1]
+	%11 = load i8* %10, align 1		; <i8> [#uses=1]
+	%12 = getelementptr i8* %j, i32 %7		; <i8*> [#uses=1]
+	store i8 %11, i8* %12, align 1
+	br label %bb7
+
+bb7:		; preds = %bb6
+	%indvar.next7 = add i32 %x.06, 1		; <i32> [#uses=2]
+	%exitcond10 = icmp ne i32 %indvar.next7, %smax9		; <i1> [#uses=1]
+	br i1 %exitcond10, label %bb6, label %bb7.bb9_crit_edge
+
+bb7.bb9_crit_edge:		; preds = %bb7
+	br label %bb9
+
+bb9:		; preds = %bb7.preheader, %bb7.bb9_crit_edge
+	br label %bb10
+
+bb10:		; preds = %bb9
+	%indvar.next11 = add i32 %y.08, 1		; <i32> [#uses=2]
+	%exitcond12 = icmp ne i32 %indvar.next11, %x		; <i1> [#uses=1]
+	br i1 %exitcond12, label %bb7.preheader, label %bb10.bb18.loopexit_crit_edge
+
+bb10.bb18.loopexit_crit_edge:		; preds = %bb10
+	br label %bb10.bb18.loopexit_crit_edge.split
+
+bb10.bb18.loopexit_crit_edge.split:		; preds = %bb.nph9, %bb10.bb18.loopexit_crit_edge
+	br label %bb18.loopexit
+
+bb.nph9:		; preds = %bb10.preheader
+	%13 = icmp ugt i32 %w, 0		; <i1> [#uses=1]
+	br i1 %13, label %bb.nph9.split, label %bb10.bb18.loopexit_crit_edge.split
+
+bb.nph9.split:		; preds = %bb.nph9
+	br label %bb7.preheader
+
+bb7.preheader:		; preds = %bb.nph9.split, %bb10
+	%y.08 = phi i32 [ 0, %bb.nph9.split ], [ %indvar.next11, %bb10 ]		; <i32> [#uses=3]
+	br i1 true, label %bb.nph7, label %bb9
+
+bb.nph5:		; preds = %bb18.loopexit
+	%14 = udiv i32 %w, 2		; <i32> [#uses=1]
+	%15 = icmp ult i32 %w, 2		; <i1> [#uses=1]
+	%16 = udiv i32 %x, 2		; <i32> [#uses=2]
+	br i1 %15, label %bb18.bb20_crit_edge.split, label %bb.nph5.split
+
+bb.nph5.split:		; preds = %bb.nph5
+	%tmp2 = icmp ugt i32 1, %16		; <i1> [#uses=1]
+	%smax3 = select i1 %tmp2, i32 1, i32 %16		; <i32> [#uses=1]
+	br label %bb13
+
+bb13:		; preds = %bb18, %bb.nph5.split
+	%y.14 = phi i32 [ 0, %bb.nph5.split ], [ %indvar.next1, %bb18 ]		; <i32> [#uses=4]
+	%17 = mul i32 %14, %y.14		; <i32> [#uses=2]
+	%18 = shl i32 %y.14, 1		; <i32> [#uses=1]
+	%19 = urem i32 %y.14, 2		; <i32> [#uses=1]
+	%20 = add i32 %19, %18		; <i32> [#uses=1]
+	%21 = mul i32 %20, %s		; <i32> [#uses=2]
+	br i1 true, label %bb.nph3, label %bb17
+
+bb.nph3:		; preds = %bb13
+	%22 = add i32 %17, %0		; <i32> [#uses=1]
+	%23 = add i32 %17, %.sum2		; <i32> [#uses=1]
+	%24 = udiv i32 %w, 2		; <i32> [#uses=2]
+	%tmp = icmp ugt i32 1, %24		; <i1> [#uses=1]
+	%smax = select i1 %tmp, i32 1, i32 %24		; <i32> [#uses=1]
+	br label %bb14
+
+bb14:		; preds = %bb15, %bb.nph3
+	%x.12 = phi i32 [ 0, %bb.nph3 ], [ %indvar.next, %bb15 ]		; <i32> [#uses=5]
+	%25 = shl i32 %x.12, 2		; <i32> [#uses=1]
+	%26 = add i32 %25, %21		; <i32> [#uses=1]
+	%27 = getelementptr i8* %r, i32 %26		; <i8*> [#uses=1]
+	%28 = load i8* %27, align 1		; <i8> [#uses=1]
+	%.sum = add i32 %22, %x.12		; <i32> [#uses=1]
+	%29 = getelementptr i8* %j, i32 %.sum		; <i8*> [#uses=1]
+	store i8 %28, i8* %29, align 1
+	%30 = shl i32 %x.12, 2		; <i32> [#uses=1]
+	%31 = or i32 %30, 2		; <i32> [#uses=1]
+	%32 = add i32 %31, %21		; <i32> [#uses=1]
+	%33 = getelementptr i8* %r, i32 %32		; <i8*> [#uses=1]
+	%34 = load i8* %33, align 1		; <i8> [#uses=1]
+	%.sum6 = add i32 %23, %x.12		; <i32> [#uses=1]
+	%35 = getelementptr i8* %j, i32 %.sum6		; <i8*> [#uses=1]
+	store i8 %34, i8* %35, align 1
+	br label %bb15
+
+bb15:		; preds = %bb14
+	%indvar.next = add i32 %x.12, 1		; <i32> [#uses=2]
+	%exitcond = icmp ne i32 %indvar.next, %smax		; <i1> [#uses=1]
+	br i1 %exitcond, label %bb14, label %bb15.bb17_crit_edge
+
+bb15.bb17_crit_edge:		; preds = %bb15
+	br label %bb17
+
+bb17:		; preds = %bb15.bb17_crit_edge, %bb13
+	br label %bb18
+
+bb18.loopexit:		; preds = %bb10.bb18.loopexit_crit_edge.split, %bb10.preheader
+	%36 = icmp ult i32 %x, 2		; <i1> [#uses=1]
+	br i1 %36, label %bb20, label %bb.nph5
+
+bb18:		; preds = %bb17
+	%indvar.next1 = add i32 %y.14, 1		; <i32> [#uses=2]
+	%exitcond4 = icmp ne i32 %indvar.next1, %smax3		; <i1> [#uses=1]
+	br i1 %exitcond4, label %bb13, label %bb18.bb20_crit_edge
+
+bb18.bb20_crit_edge:		; preds = %bb18
+	br label %bb18.bb20_crit_edge.split
+
+bb18.bb20_crit_edge.split:		; preds = %bb18.bb20_crit_edge, %bb.nph5
+	br label %bb20
+
+bb20:		; preds = %bb18.bb20_crit_edge.split, %bb18.loopexit
+	switch i32 %d, label %return [
+		i32 3, label %bb22
+		i32 1, label %bb29
+	]
+
+bb22:		; preds = %bb20
+	%37 = mul i32 %x, %w		; <i32> [#uses=1]
+	%38 = udiv i32 %37, 4		; <i32> [#uses=1]
+	%.sum3 = add i32 %38, %.sum2		; <i32> [#uses=2]
+	%39 = add i32 %x, 15		; <i32> [#uses=1]
+	%40 = and i32 %39, -16		; <i32> [#uses=1]
+	%41 = add i32 %w, 15		; <i32> [#uses=1]
+	%42 = and i32 %41, -16		; <i32> [#uses=1]
+	%43 = mul i32 %40, %s		; <i32> [#uses=1]
+	%44 = icmp ugt i32 %x, 0		; <i1> [#uses=1]
+	br i1 %44, label %bb.nph, label %bb26
+
+bb.nph:		; preds = %bb22
+	br label %bb23
+
+bb23:		; preds = %bb24, %bb.nph
+	%y.21 = phi i32 [ 0, %bb.nph ], [ %indvar.next5, %bb24 ]		; <i32> [#uses=3]
+	%45 = mul i32 %y.21, %42		; <i32> [#uses=1]
+	%.sum1 = add i32 %45, %43		; <i32> [#uses=1]
+	%46 = getelementptr i8* %r, i32 %.sum1		; <i8*> [#uses=1]
+	%47 = mul i32 %y.21, %w		; <i32> [#uses=1]
+	%.sum5 = add i32 %47, %.sum3		; <i32> [#uses=1]
+	%48 = getelementptr i8* %j, i32 %.sum5		; <i8*> [#uses=1]
+	tail call void @llvm.memcpy.i32(i8* %48, i8* %46, i32 %w, i32 1)
+	br label %bb24
+
+bb24:		; preds = %bb23
+	%indvar.next5 = add i32 %y.21, 1		; <i32> [#uses=2]
+	%exitcond6 = icmp ne i32 %indvar.next5, %x		; <i1> [#uses=1]
+	br i1 %exitcond6, label %bb23, label %bb24.bb26_crit_edge
+
+bb24.bb26_crit_edge:		; preds = %bb24
+	br label %bb26
+
+bb26:		; preds = %bb24.bb26_crit_edge, %bb22
+	%49 = mul i32 %x, %w		; <i32> [#uses=1]
+	%.sum4 = add i32 %.sum3, %49		; <i32> [#uses=1]
+	%50 = getelementptr i8* %j, i32 %.sum4		; <i8*> [#uses=1]
+	%51 = mul i32 %x, %w		; <i32> [#uses=1]
+	%52 = udiv i32 %51, 2		; <i32> [#uses=1]
+	tail call void @llvm.memset.i32(i8* %50, i8 -128, i32 %52, i32 1)
+	ret void
+
+bb29:		; preds = %bb20, %entry
+	%53 = add i32 %w, 15		; <i32> [#uses=1]
+	%54 = and i32 %53, -16		; <i32> [#uses=1]
+	%55 = icmp ugt i32 %x, 0		; <i1> [#uses=1]
+	br i1 %55, label %bb.nph11, label %bb33
+
+bb.nph11:		; preds = %bb29
+	br label %bb30
+
+bb30:		; preds = %bb31, %bb.nph11
+	%y.310 = phi i32 [ 0, %bb.nph11 ], [ %indvar.next13, %bb31 ]		; <i32> [#uses=3]
+	%56 = mul i32 %y.310, %54		; <i32> [#uses=1]
+	%57 = getelementptr i8* %r, i32 %56		; <i8*> [#uses=1]
+	%58 = mul i32 %y.310, %w		; <i32> [#uses=1]
+	%59 = getelementptr i8* %j, i32 %58		; <i8*> [#uses=1]
+	tail call void @llvm.memcpy.i32(i8* %59, i8* %57, i32 %w, i32 1)
+	br label %bb31
+
+bb31:		; preds = %bb30
+	%indvar.next13 = add i32 %y.310, 1		; <i32> [#uses=2]
+	%exitcond14 = icmp ne i32 %indvar.next13, %x		; <i1> [#uses=1]
+	br i1 %exitcond14, label %bb30, label %bb31.bb33_crit_edge
+
+bb31.bb33_crit_edge:		; preds = %bb31
+	br label %bb33
+
+bb33:		; preds = %bb31.bb33_crit_edge, %bb29
+	%60 = mul i32 %x, %w		; <i32> [#uses=1]
+	%61 = getelementptr i8* %j, i32 %60		; <i8*> [#uses=1]
+	%62 = mul i32 %x, %w		; <i32> [#uses=1]
+	%63 = udiv i32 %62, 2		; <i32> [#uses=1]
+	tail call void @llvm.memset.i32(i8* %61, i8 -128, i32 %63, i32 1)
+	ret void
+
+return:		; preds = %bb20
+	ret void
+}
+
 declare void @llvm.memcpy.i32(i8*, i8*, i32, i32) nounwind
 
 declare void @llvm.memset.i32(i8*, i8, i32, i32) nounwind
diff --git a/test/CodeGen/X86/optimize-max-1.ll b/test/CodeGen/X86/optimize-max-1.ll
new file mode 100644
index 0000000000..084e1818f5
--- /dev/null
+++ b/test/CodeGen/X86/optimize-max-1.ll
@@ -0,0 +1,78 @@
+; RUN: llvm-as < %s | llc -march=x86-64 | not grep cmov
+
+; LSR should be able to eliminate both smax and umax expressions
+; in loop trip counts.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+
+define void @fs(double* nocapture %p, i64 %n) nounwind {
+entry:
+	%tmp = icmp slt i64 %n, 1		; <i1> [#uses=1]
+	%smax = select i1 %tmp, i64 1, i64 %n		; <i64> [#uses=1]
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%i.0 = phi i64 [ 0, %entry ], [ %0, %bb ]		; <i64> [#uses=2]
+	%scevgep = getelementptr double* %p, i64 %i.0		; <double*> [#uses=1]
+	store double 0.000000e+00, double* %scevgep, align 8
+	%0 = add i64 %i.0, 1		; <i64> [#uses=2]
+	%exitcond = icmp eq i64 %0, %smax		; <i1> [#uses=1]
+	br i1 %exitcond, label %return, label %bb
+
+return:		; preds = %bb
+	ret void
+}
+
+define void @bs(double* nocapture %p, i64 %n) nounwind {
+entry:
+	%tmp = icmp sge i64 %n, 1		; <i1> [#uses=1]
+	%smax = select i1 %tmp, i64 %n, i64 1		; <i64> [#uses=1]
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%i.0 = phi i64 [ 0, %entry ], [ %0, %bb ]		; <i64> [#uses=2]
+	%scevgep = getelementptr double* %p, i64 %i.0		; <double*> [#uses=1]
+	store double 0.000000e+00, double* %scevgep, align 8
+	%0 = add i64 %i.0, 1		; <i64> [#uses=2]
+	%exitcond = icmp eq i64 %0, %smax		; <i1> [#uses=1]
+	br i1 %exitcond, label %return, label %bb
+
+return:		; preds = %bb
+	ret void
+}
+
+define void @fu(double* nocapture %p, i64 %n) nounwind {
+entry:
+	%tmp = icmp eq i64 %n, 0		; <i1> [#uses=1]
+	%umax = select i1 %tmp, i64 1, i64 %n		; <i64> [#uses=1]
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%i.0 = phi i64 [ 0, %entry ], [ %0, %bb ]		; <i64> [#uses=2]
+	%scevgep = getelementptr double* %p, i64 %i.0		; <double*> [#uses=1]
+	store double 0.000000e+00, double* %scevgep, align 8
+	%0 = add i64 %i.0, 1		; <i64> [#uses=2]
+	%exitcond = icmp eq i64 %0, %umax		; <i1> [#uses=1]
+	br i1 %exitcond, label %return, label %bb
+
+return:		; preds = %bb
+	ret void
+}
+
+define void @bu(double* nocapture %p, i64 %n) nounwind {
+entry:
+	%tmp = icmp ne i64 %n, 0		; <i1> [#uses=1]
+	%umax = select i1 %tmp, i64 %n, i64 1		; <i64> [#uses=1]
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%i.0 = phi i64 [ 0, %entry ], [ %0, %bb ]		; <i64> [#uses=2]
+	%scevgep = getelementptr double* %p, i64 %i.0		; <double*> [#uses=1]
+	store double 0.000000e+00, double* %scevgep, align 8
+	%0 = add i64 %i.0, 1		; <i64> [#uses=2]
+	%exitcond = icmp eq i64 %0, %umax		; <i1> [#uses=1]
+	br i1 %exitcond, label %return, label %bb
+
+return:		; preds = %bb
+	ret void
+}