SCEVExpander: Fold constant PHIs harder. The logic below only understands proper IVs.

PR20093.

llvm-svn: 211433

2 files changed, 53 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
index b5070434d14..8c75b0db70f 100644
--- a/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/llvm/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/DataLayout.h"
@@ -1706,7 +1707,7 @@ unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
 
     // Fold constant phis. They may be congruent to other constant phis and
     // would confuse the logic below that expects proper IVs.
-    if (Value *V = Phi->hasConstantValue()) {
+    if (Value *V = SimplifyInstruction(Phi, SE.DL, SE.TLI, SE.DT)) {
       Phi->replaceAllUsesWith(V);
       DeadInsts.push_back(Phi);
       ++NumElim;
diff --git a/llvm/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll b/llvm/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll
new file mode 100644
index 00000000000..3df4c210b4a
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll
@@ -0,0 +1,51 @@
+; RUN: opt -S -loop-unswitch -instcombine -indvars < %s | FileCheck %s
+
+@c = external global i32**, align 8
+
+define void @test1() {
+entry:
+  br i1 undef, label %for.end12, label %for.cond.preheader
+
+for.cond.preheader:                               ; preds = %entry
+  %0 = load i32*** @c, align 8
+  %1 = load i32** %0, align 8
+  %2 = load i32* %1, align 4
+  br label %for.body
+
+for.body:                                         ; preds = %for.cond.backedge, %for.body9.us, %for.cond.preheader
+  %3 = phi i32* [ %1, %for.cond.preheader ], [ %3, %for.cond.backedge ], [ %6, %for.body9.us ]
+  %4 = phi i32 [ %2, %for.cond.preheader ], [ undef, %for.cond.backedge ], [ %7, %for.body9.us ]
+  %i.024 = phi i32 [ 0, %for.cond.preheader ], [ %inc, %for.cond.backedge ], [ 0, %for.body9.us ]
+  %tobool1 = icmp eq i32 %4, 0
+  br i1 %tobool1, label %if.end, label %for.cond.backedge
+
+if.end:                                           ; preds = %for.body
+  %5 = load i32* %3, align 4
+  %tobool4 = icmp eq i32 %5, 0
+  br i1 %tobool4, label %for.cond3, label %for.body9.preheader
+
+for.body9.preheader:                              ; preds = %if.end
+  %tobool8 = icmp eq i32 %i.024, 1
+  br i1 %tobool8, label %for.body9.us, label %for.body9
+
+for.body9.us:                                     ; preds = %for.body9.preheader
+  %6 = load i32** undef, align 8
+  %7 = load i32* %6, align 4
+  br label %for.body
+
+for.cond3:                                        ; preds = %for.cond3, %if.end
+  br label %for.cond3
+
+for.body9:                                        ; preds = %for.body9, %for.body9.preheader
+  br label %for.body9
+
+for.cond.backedge:                                ; preds = %for.body
+  %inc = add nsw i32 %i.024, 1
+  br i1 false, label %for.body, label %for.end12
+
+for.end12:                                        ; preds = %for.cond.backedge, %entry
+  ret void
+
+; CHECK-LABEL: @test1
+; CHECK-NOT: phi
+}