Don't attempt to simplify an non-affine IV expression if it can't

be simplified to a loop-invariant value. This fixes PR4315.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72798 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 53 insertions, 12 deletions

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index ca7aa7bd30..af61eae16f 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -465,17 +465,6 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
       // Compute the final addrec to expand into code.
       SCEVHandle AR = IU->getReplacementExpr(*UI);
 
-      // FIXME: It is an extremely bad idea to indvar substitute anything more
-      // complex than affine induction variables.  Doing so will put expensive
-      // polynomial evaluations inside of the loop, and the str reduction pass
-      // currently can only reduce affine polynomials.  For now just disable
-      // indvar subst on anything more complex than an affine addrec, unless
-      // it can be expanded to a trivial value.
-      if (!Stride->isLoopInvariant(L) &&
-          !isa<SCEVConstant>(AR) &&
-          L->contains(User->getParent()))
-        continue;
-
       Value *NewVal = 0;
       if (AR->isLoopInvariant(L)) {
         BasicBlock::iterator I = Rewriter.getInsertionPoint();
@@ -487,6 +476,15 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
         Rewriter.setInsertionPoint(I);
         ++NumReplaced;
       } else {
+        // FIXME: It is an extremely bad idea to indvar substitute anything more
+        // complex than affine induction variables.  Doing so will put expensive
+        // polynomial evaluations inside of the loop, and the str reduction pass
+        // currently can only reduce affine polynomials.  For now just disable
+        // indvar subst on anything more complex than an affine addrec, unless
+        // it can be expanded to a trivial value.
+        if (!Stride->isLoopInvariant(L))
+          continue;
+
         const Type *IVTy = Offset->getType();
         const Type *UseTy = Op->getType();
 
@@ -520,7 +518,7 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, const Type *LargestType,
         // induction variable, still in the canonical induction variable's
         // type, so that all expanded arithmetic is done in the same type.
         SCEVHandle NewAR = SE->getAddRecExpr(SE->getIntegerSCEV(0, LargestType),
-                                           PromotedStride, L);
+                                             PromotedStride, L);
         // Add the PromotedOffset as a separate step, because it may not be
         // loop-invariant.
         NewAR = SE->getAddExpr(NewAR, PromotedOffset);
diff --git a/test/Transforms/IndVarSimplify/variable-stride-ivs.ll b/test/Transforms/IndVarSimplify/variable-stride-ivs-0.ll
index 759ba8e177..759ba8e177 100644
--- a/test/Transforms/IndVarSimplify/variable-stride-ivs.ll
+++ b/test/Transforms/IndVarSimplify/variable-stride-ivs-0.ll
diff --git a/test/Transforms/IndVarSimplify/variable-stride-ivs-1.ll b/test/Transforms/IndVarSimplify/variable-stride-ivs-1.ll
new file mode 100644
index 0000000000..075e899cd9
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/variable-stride-ivs-1.ll
@@ -0,0 +1,43 @@
+; RUN: llvm-as < %s | opt -indvars
+; PR4315
+
+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-f80:128:128"
+target triple = "x86_64-undermydesk-freebsd8.0"
+	%struct.mbuf = type <{ %struct.mbuf*, i8*, i32, i8, i8, i8, i8 }>
+
+define i32 @crash(%struct.mbuf* %m) nounwind {
+entry:
+	br label %for.cond
+
+for.cond:		; preds = %if.end, %entry
+	%i.0 = phi i32 [ 0, %entry ], [ %inc, %if.end ]		; <i32> [#uses=3]
+	%chksum.0 = phi i8 [ 0, %entry ], [ %conv3, %if.end ]		; <i8> [#uses=3]
+	%cmp = icmp slt i32 %i.0, 1		; <i1> [#uses=1]
+	br i1 %cmp, label %for.body, label %do.body
+
+for.body:		; preds = %for.cond
+	br i1 undef, label %if.end, label %do.body
+
+if.end:		; preds = %for.body
+	%i.02 = trunc i32 %i.0 to i8		; <i8> [#uses=1]
+	%conv3 = add i8 %chksum.0, %i.02		; <i8> [#uses=1]
+	%inc = add i32 %i.0, 1		; <i32> [#uses=1]
+	br label %for.cond
+
+do.body:		; preds = %do.cond, %for.body, %for.cond
+	%chksum.2 = phi i8 [ undef, %do.cond ], [ %chksum.0, %for.body ], [ %chksum.0, %for.cond ]		; <i8> [#uses=1]
+	br i1 undef, label %do.cond, label %bb.nph
+
+bb.nph:		; preds = %do.body
+	br label %while.body
+
+while.body:		; preds = %while.body, %bb.nph
+	%chksum.13 = phi i8 [ undef, %while.body ], [ %chksum.2, %bb.nph ]		; <i8> [#uses=0]
+	br i1 undef, label %do.cond, label %while.body
+
+do.cond:		; preds = %while.body, %do.body
+	br i1 false, label %do.end, label %do.body
+
+do.end:		; preds = %do.cond
+	ret i32 0
+}