Fix SCEVExpander to handle loops with no preheader when LSR gives it a

"phony" insertion point.

Fixes rdar://10619599: "SelectionDAGBuilder shouldn't visit PHI nodes!" assert

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147439 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index 5f83914cb273c1b457ee49053e21a1f2d34f1f87..0a3cda998f49c073eece0205c9b4745cf4cd5879 100644 (file)
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -1443,6 +1443,12 @@ Value *SCEVExpander::expand(const SCEV *S) {
       if (!L) break;
       if (BasicBlock *Preheader = L->getLoopPreheader())
         InsertPt = Preheader->getTerminator();
+      else {
+        // LSR sets the insertion point for AddRec start/step values to the
+        // block start to simplify value reuse, even though it's an invalid
+        // position. SCEVExpander must correct for this in all cases.
+        InsertPt = L->getHeader()->getFirstInsertionPt();
+      }
     } else {
       // If the SCEV is computable at this level, insert it into the header
       // after the PHIs (and after any other instructions that we've inserted

diff --git a/test/Transforms/LoopStrengthReduce/2012-02-nopreheader.ll b/test/Transforms/LoopStrengthReduce/2012-02-nopreheader.ll
new file mode 100644 (file)
index 0000000..78d4ef7
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/2012-02-nopreheader.ll
@@ -0,0 +1,50 @@
+; RUN: opt -loop-reduce -S < %s | FileCheck %s
+;
+; <rdar://10619599> "SelectionDAGBuilder shouldn't visit PHI nodes!" assert.
+
+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-f128:128:128-n8:16:32"
+target triple = "i386-apple-darwin"
+
+; LSR should convert the inner loop (bb7.us) IV (j.01.us) into float*.
+; This involves a nested AddRec, the outer AddRec's loop invariant components
+; cannot find a preheader, so they should be expanded in the loop header
+; (bb7.lr.ph.us) below the existing phi i.12.us.
+; CHECK: @nopreheader
+; CHECK: bb7.lr.ph.us:
+; CHECK: %lsr.iv = phi float*
+; CHECK: bb7.us:
+; CHECK: %lsr.iv2 = phi float*
+define void @nopreheader(float* nocapture %a, i32 %n) nounwind {
+entry:
+  %0 = sdiv i32 %n, undef
+  indirectbr i8* undef, [label %bb10.preheader]
+
+bb10.preheader:                                   ; preds = %bb4
+  indirectbr i8* undef, [label %bb8.preheader.lr.ph, label %return]
+
+bb8.preheader.lr.ph:                              ; preds = %bb10.preheader
+  indirectbr i8* null, [label %bb7.lr.ph.us, label %bb9]
+
+bb7.lr.ph.us:                                     ; preds = %bb9.us, %bb8.preheader.lr.ph
+  %i.12.us = phi i32 [ %2, %bb9.us ], [ 0, %bb8.preheader.lr.ph ]
+  %tmp30 = mul i32 %0, %i.12.us
+  indirectbr i8* undef, [label %bb7.us]
+
+bb7.us:                                           ; preds = %bb7.lr.ph.us, %bb7.us
+  %j.01.us = phi i32 [ 0, %bb7.lr.ph.us ], [ %1, %bb7.us ]
+  %tmp31 = add i32 %tmp30, %j.01.us
+  %scevgep9 = getelementptr float* %a, i32 %tmp31
+  store float undef, float* %scevgep9, align 1
+  %1 = add nsw i32 %j.01.us, 1
+  indirectbr i8* undef, [label %bb9.us, label %bb7.us]
+
+bb9.us:                                           ; preds = %bb7.us
+  %2 = add nsw i32 %i.12.us, 1
+  indirectbr i8* undef, [label %bb7.lr.ph.us, label %return]
+
+bb9:                                              ; preds = %bb9, %bb8.preheader.lr.ph
+  indirectbr i8* undef, [label %bb9, label %return]
+
+return:                                           ; preds = %bb9, %bb9.us, %bb10.preheader
+  ret void
+}